Patent Publication Number: US-2017370167-A1

Title: Mud-gas separator apparatus and methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of, and priority to, U.S. patent application No. 62/089,913, filed Dec. 10, 2014, the entire disclosure of which is hereby incorporated herein by reference. 
     This application claims the benefit of the filing date of, and priority to, U.S. patent application No. 62/173,633, filed Jun. 10, 2015, the entire disclosure of which is hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates in general to mud-gas separators and, in particular, to automatically controlling one or more aspects of a mud-gas separator apparatus. 
     BACKGROUND OF THE DISCLOSURE 
     During the drilling of an oil or gas well, different materials may be discharged from the well. The discharged materials may include mixtures of solid, liquid, and gas materials. A mud-gas separator may be used to separate the gas materials from the solid and liquid materials. After separation, the gas materials flow out through a gas vent line, and the solid and liquid materials flow out through a slurry return line. In some cases, a mud-gas separator apparatus may have too large of a footprint, taking up too much ground space at a wellsite. Also, the mud-gas separator apparatus may have too large of a volume, taking up too much volumetric space during transportation to the wellsite and/or during operation at the wellsite. Further, the gas materials may flow out of the slurry return line, rather than out of the gas vent line, increasing the risk of fire at the wellsite. Still further, personnel at the wellsite may not be aware that the amount of solid and liquid materials in the mud-gas separator vessel at any given time is either too high or too low. Therefore, what is needed is an apparatus, method, or kit that addresses one or more of the foregoing issues, or other issue(s). 
     SUMMARY 
     In a first aspect, there is provided an apparatus that includes a mud-gas separator vessel adapted to receive a multiphase flow and separate gas materials therefrom. The mud-gas separator vessel defines an internal region in which a slurry is adapted to be collected, and the slurry defines a fluid level within the internal region. At least one sensor is operably coupled to the mud-gas separator vessel and is adapted to measure the fluid level when the slurry is collected in the internal region. An electronic controller is in communication with the at least one sensor and is adapted to receive from the at least one sensor measurement data associated with the measurement of the fluid level. A control valve is in communication with the electronic controller and is adapted to control discharge of the slurry out of the mud-gas separator vessel. The electronic controller is adapted to automatically control the control valve based on the measurement data received from the at least one sensor and thus actively control the fluid level within the internal region using the control valve. 
     In an exemplary embodiment, the control valve includes an electric actuator and a rotary control valve operably coupled thereto. 
     In another exemplary embodiment, the at least one sensor includes a guided wave level sensor, the guided wave level sensor including a probe, and the apparatus further includes a level sensor housing assembly connected to the mud-gas separator vessel, the level sensor housing assembly including a tubular member within which at least a portion of the probe extends. 
     In yet another exemplary embodiment, the level sensor housing assembly further includes first and second fittings between which the tubular member extends; and first and second isolation valves connected to the first and second fittings, respectively, and to the mud-gas separator vessel; wherein the tubular member is spaced from the mud-gas separator vessel; and wherein the guided wave level sensor is connected to the second fitting and the probe extends through the second fitting and at least into the tubular member. 
     In certain exemplary embodiments, the electronic controller includes one or more processors; a non-transitory computer readable medium operably coupled to the one or more processors; and a plurality of instructions stored on the non-transitory computer readable medium and executable by the one or more processors, the plurality of instructions including instructions that cause the one or more processors to automatically control the control valve based on the measurement data. 
     In an exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to automatically further close the control valve in response to determining that the fluid level is decreasing too rapidly; and instructions that cause the one or more processors to automatically open, or further open, the control valve in response to determining that the fluid level is increasing too rapidly. 
     In another exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to determine that the fluid level is not within a stability zone; and instructions that cause the one or more processors to automatically adjust a valve position of the control valve in response to determining that the fluid level is not within the stability zone. 
     In yet another exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to determine a proportional parameter; and instructions that cause the one or more processors to determine a differential parameter. 
     In still yet another exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve further include instructions that cause the one or more processors to determine a valve position change based on the proportional and differential parameters if either: the proportional parameter is not less than a proportional fluctuation constant, or the differential parameter is not less than a differential fluctuation constant; and instructions that cause the one or more processors to set a change in a valve position of the control valve to zero degrees if: the proportional parameter is less than the proportional fluctuation constant, and the differential parameter is less than the differential fluctuation constant. 
     In certain exemplary embodiments, the instructions that cause the one or more processors to automatically control the control valve further include instructions that cause the one or more processors to determine a maximum allowable valve position change if a rate of change of the valve position due to the valve position change based on the proportional and differential parameters would not be less than an allowable angular velocity of the control valve. 
     In an exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve further include instructions that cause the one or more processors to update the valve position of the control valve by the valve position change based on the proportional and differential parameters if: the rate of change of the valve position due to the valve position change based on the proportional and differential parameters would be less than the allowable angular velocity of the control valve; and either: the proportional parameter is not less than the proportional fluctuation constant, or the differential parameter is not less than the differential fluctuation constant; instructions that cause the one or more processors to update the valve position of the control valve by the maximum allowable valve position change if: the rate of change of the valve position due to the valve position change based on the proportional and differential parameters would not be less than the allowable angular velocity of the control valve; and either: the proportional parameter is not less than the proportional fluctuation constant, or the differential parameter is not less than the differential fluctuation constant; and instructions that cause the one or more processors to update the valve position of the control valve by zero degrees if: the proportional parameter is less than a proportional fluctuation constant; and the differential parameter is less than a differential fluctuation constant. 
     In a second aspect, there is provided a method of actively controlling a fluid level in an internal region defined by a mud-gas separator vessel, the fluid level being defined by a slurry collected within the internal region, the method including automatically measuring, using at least one sensor, the fluid level in the internal region; automatically transmitting, using the at least one sensor, measurement data to an electronic controller, the measurement data being associated with the measurement of the fluid level defined by the slurry; and automatically controlling, using the electronic controller, a control valve based on the measurement data; wherein the automatic control of the control valve by the electronic controller automatically controls discharge of the slurry out of the mud-gas separator vessel and thus actively controls the fluid level. 
     In an exemplary embodiment, automatically controlling the control valve includes automatically further closing the control valve in response to determining that the fluid level is decreasing too rapidly; and automatically opening, or further opening, the control valve in response to determining that the fluid level is increasing too rapidly. 
     In another exemplary embodiment, automatically controlling the control valve includes automatically determining that the fluid level is not within a stability zone; and automatically adjusting the valve position of the control valve in response to determining that the fluid level is not within the stability zone. 
     In yet another exemplary embodiment, automatically controlling the control valve includes automatically determining a proportional parameter; and automatically determining a differential parameter. 
     In still yet another exemplary embodiment, automatically controlling the control valve further includes automatically determining a valve position change based on the proportional and differential parameters if either: the proportional parameter is not less than a proportional fluctuation constant, or the differential parameter is not less than a differential fluctuation constant; and automatically setting a change in a valve position of the control valve to zero degrees if: the proportional parameter is less than the proportional fluctuation constant, and the differential parameter is less than the differential fluctuation constant. 
     In certain exemplary embodiments, automatically controlling the control valve further includes automatically determining a maximum allowable valve position change if a rate of change of the valve position due to the valve position change based on the proportional and differential parameters would not be less than an allowable angular velocity of the control valve. 
     In an exemplary embodiment, automatically controlling the control valve further includes automatically updating the valve position of the control valve by the valve position change based on the proportional and differential parameters if: the rate of change of the valve position due to the valve position change based on the proportional and differential parameters would be less than the allowable angular velocity of the control valve; and either: the proportional parameter is not less than the proportional fluctuation constant, or the differential parameter is not less than the differential fluctuation constant; automatically updating the valve position of the control valve by the maximum allowable valve position change if: the rate of change of the valve position due to the valve position change based on the proportional and differential parameters would not be less than the allowable angular velocity of the control valve; and either: the proportional parameter is not less than the proportional fluctuation constant, or the differential parameter is not less than the differential fluctuation constant; and automatically updating the valve position of the control valve by zero degrees if: the proportional parameter is less than the proportional fluctuation constant; and the differential parameter is less than the differential fluctuation constant. 
     In a third aspect, there is provided a method of retrofitting a mud-gas separator apparatus, the mud-gas separator apparatus including a mud-gas separator vessel and a slurry return line connected thereto, the method including operably coupling at least one sensor to the mud-gas separator vessel; operably coupling an electronic controller to the at least one sensor; operably coupling a control valve to the electronic controller; and connecting the control valve to the slurry return line. 
     In another exemplary embodiment, operably coupling the at least one sensor to the mud-gas separator vessel includes operably coupling a guided wave level sensor to the mud-gas separator vessel. 
     In yet another exemplary embodiment, operably coupling the guided wave level sensor to the mud-gas separator vessel includes connecting the guided wave level sensor to a level sensor housing assembly; and connecting the level sensor housing assembly to the mud-gas separator vessel. 
     In certain exemplary embodiments, the guided wave level sensor includes a probe; wherein the level sensor housing assembly includes a tubular member; first and second fittings between which the tubular member extends; and first and second isolation valves connected to the first and second fittings, respectively; wherein connecting the guided wave level sensor to the level sensor housing assembly includes inserting the probe through the second fitting and into at least the tubular member; and connecting the guided wave level sensor to the second fitting; and wherein connecting the level sensor housing assembly to the mud-gas separator vessel includes connecting the first and second isolation valves to the mud-gas separator vessel so that the tubular member is spaced from the mud-gas separator vessel. 
     In an exemplary embodiment, operably coupling the control valve to the electronic controller includes operably coupling an electric actuator to the electronic controller; and operably coupling a rotary control valve to the electric actuator. 
     In another exemplary embodiment, the mud-gas separator vessel defines an internal region; wherein the at least one sensor is adapted to measure the fluid level when a slurry is collected in the internal region; wherein the control valve is adapted to control discharge of the slurry out of the mud-gas separator vessel; and wherein the electronic controller is adapted to receive from the at least one sensor measurement data associated with the measurement of the fluid level, and is further adapted to automatically control the control valve based on the measurement data and thus actively control the fluid level within the internal region using the control valve. 
     In a fourth aspect, there is provided a kit for actively controlling a fluid level within an internal region defined by a mud-gas separator vessel, the fluid level being defined by a slurry collected within the internal region, the kit including at least one sensor adapted to be operably coupled to the mud-gas separator vessel, and to measure the fluid level when the slurry is collected in the internal region; an electronic controller adapted to be in communication with the at least one sensor, and to receive from the at least one sensor measurement data associated with the measurement of the fluid level; and a control valve adapted to be in communication with the electronic controller, and to control discharge of the slurry out of the mud-gas separator vessel; wherein the electronic controller is adapted to automatically control the control valve based on the measurement data received from the at least one sensor and thus is adapted to actively control the fluid level within the internal region using the control valve. 
     In an exemplary embodiment, the at least one sensor includes a guided wave level sensor, the guided wave level sensor including a probe; and wherein the kit further includes a level sensor housing assembly adapted to be connected to the mud-gas separator vessel, the level sensor housing assembly including a tubular member within which at least a portion of the probe extends. 
     In another exemplary embodiment, the level sensor housing assembly further includes first and second fittings between which the tubular member extends; and first and second isolation valves connected to the first and second fittings, respectively, and adapted to be connected to the mud-gas separator vessel; wherein the guided wave level sensor is connected to the second fitting and the probe extends through the second fitting and at least into the tubular member. 
     In yet another exemplary embodiment, the electronic controller includes one or more processors; a non-transitory computer readable medium operably coupled to the one or more processors; and a plurality of instructions stored on the non-transitory computer readable medium and executable by the one or more processors, the plurality of instructions including instructions that cause the one or more processors to automatically control the control valve based on the measurement data. 
     In certain exemplary embodiments, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to automatically further close the control valve in response to determining that the fluid level is decreasing too rapidly; and instructions that cause the one or more processors to automatically open, or further open, the control valve in response to determining that the fluid level is increasing too rapidly. 
     In an exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to determine that the fluid level is not within a stability zone; and instructions that cause the one or more processors to automatically adjust a valve position of the control valve in response to determining that the fluid level is not within the stability zone. 
     In another exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to determine a proportional parameter; and instructions that cause the one or more processors to determine a differential parameter. 
     In yet another exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve include instructions that cause the one or more processors to determine a valve position change based on the proportional and differential parameters if either: the proportional parameter is not less than a proportional fluctuation constant, or the differential parameter is not less than a differential fluctuation constant; and instructions that cause the one or more processors to set a change in a valve position of the control valve to zero degrees if: the proportional parameter is less than the proportional fluctuation constant, and the differential parameter is less than the differential fluctuation constant. 
     In still yet another exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve further include instructions that cause the one or more processors to determine a maximum allowable valve position change if a rate of change of the valve position due to the valve position change based on the proportional and differential parameters is not less than an allowable angular velocity of the control valve. 
     In certain exemplary embodiment, the instructions that cause the one or more processors to automatically control the control valve further include instructions that cause the one or more processors to update the valve position of the control valve by the valve position change based on the proportional and differential parameters if: the rate of change of the valve position due to the valve position change based on the proportional and differential parameters would be less than the allowable angular velocity of the control valve; and either: the proportional parameter is not less than the proportional fluctuation constant, or the differential parameter is not less than the differential fluctuation constant; instructions that cause the one or more processors to update the valve position of the control valve by the maximum allowable valve position change if: the rate of change of the valve position due to the valve position change based on the proportional and differential parameters is not less than the allowable angular velocity of the control valve; and either: the proportional parameter is not less than the proportional fluctuation constant, or the differential parameter is not less than the differential fluctuation constant; and instructions that cause the one or more processors to update the valve position of the control valve by zero degrees if: the proportional parameter is less than the proportional fluctuation constant; and the differential parameter is less than the differential fluctuation constant. 
     Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed. 
    
    
     
       DESCRIPTION OF FIGURES 
       The accompanying drawings facilitate an understanding of the various embodiments. 
         FIG. 1  is a diagrammatic illustration of a mud-gas separator apparatus, according to an exemplary embodiment. 
         FIG. 2  is a perspective view of a portion of the mud-gas separator apparatus of  FIG. 1 , according to an exemplary embodiment. 
         FIG. 3  is a front elevational view of the portion of  FIG. 2 , according to an exemplary embodiment. 
         FIG. 4  is a right side elevational view of the portion of  FIGS. 2 and 3 , according to an exemplary embodiment. 
         FIG. 5  is a top plan view of the portion of  FIGS. 2-4 , according to an exemplary embodiment. 
         FIG. 6  is a perspective view of another portion of the mud-gas separator apparatus of  FIG. 1 , according to an exemplary embodiment. 
         FIG. 7  is a perspective view of the portion of  FIG. 6  and further illustrates internal components of the mud-gas separator apparatus, according to an exemplary embodiment. 
         FIG. 8  is a left side elevational view of yet another portion of the mud-gas separator apparatus of  FIG. 1  and further illustrates internal components of the mud-gas separator apparatus, according to an exemplary embodiment. 
         FIG. 9  is a diagrammatic illustration of a mud-gas separator apparatus according to another exemplary embodiment. 
         FIG. 10  is a flow chart illustration of a method of retrofitting a mud-gas separator apparatus, according to an exemplary embodiment. 
         FIG. 11  is a diagrammatic illustration of the mud-gas separator apparatus referenced in the method of  FIG. 10 , according to an exemplary embodiment. 
         FIG. 12  is a diagrammatic illustration of a mud-gas separator apparatus, according to an exemplary embodiment. 
         FIG. 13  is a perspective view of components of the mud-gas separator apparatus of  FIG. 12 , according to an exemplary embodiment. 
         FIG. 14A  is enlarged view of a portion of the components of  FIG. 13 , according to an exemplary embodiment. 
         FIG. 14B  is a perspective view of some of the components of the mud-gas separator apparatus shown in  FIGS. 13 and 14A , according to an exemplary embodiment. 
         FIG. 15  is a flow chart illustration of a method of controlling a control valve, according to an exemplary embodiment. 
         FIG. 16  is a diagrammatic illustration of a user interface according to an exemplary experimental embodiment, the user interface including an exemplary experimental embodiment of output generated during a simulation of the execution of the method of  FIG. 15 . 
         FIG. 17  is a view similar to that of  FIG. 16 , but depicting the user interface according to another exemplary experimental embodiment, the user interface including another exemplary experimental embodiment of output generated during a simulation of the execution of the method of  FIG. 15 . 
         FIG. 19  is a flow chart illustration of a method of retrofitting a mud-gas separator apparatus, according to an exemplary embodiment. 
         FIG. 20  is a flow chart illustration of a method of controlling a control valve, according to an exemplary embodiment. 
         FIG. 21  is a flow chart illustration of a step of the method of  FIG. 20 , according to an exemplary embodiment. 
         FIG. 22  is a diagrammatic illustration of the response of an exemplary experimental embodiment of the mud-gas separator apparatus of  FIG. 12  to a rapid increase in flow rate, according to an exemplary experimental embodiment. 
         FIG. 23  is a diagrammatic illustration of the response of an exemplary experimental embodiment of the mud-gas separator apparatus of  FIG. 12  to a rapid decrease in flow rate, according to an exemplary experimental embodiment. 
         FIG. 24  is a diagrammatic illustration of the response of an exemplary experimental embodiment of the mud-gas separator apparatus of  FIG. 12  to a disturbance, or temporary spike, in flow rate, according to an exemplary experimental embodiment. 
         FIG. 25  is a diagrammatic illustration of a node for implementing one or more exemplary embodiments of the present disclosure, according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In an exemplary embodiment, as illustrated in  FIG. 1 , an apparatus is generally referred to by the reference numeral  10  and includes a mud-gas separator vessel  12  and a guided wave level sensor  14  operably coupled thereto. An electronic controller  16  is operably coupled to, and in communication with, the guided wave level sensor  14 . A high level alarm  18  is operably coupled to, and in communication with, the electronic controller  16 . A low level alarm  19  is operably coupled to, and in communication with, the electronic controller  16 . The mud-gas separator vessel  12  includes an inlet  12   a  at an upper end portion thereof, a gas vent  12   b  at a top portion thereof, and an outlet  12   c  at a lower end portion thereof. The mud-gas separator  12  defines an internal region  12   d , with which the inlet  12   a , the gas vent  12   b , and the outlet  12   c  are in fluid communication. Baffle plates  12   e ,  12   f , and  12   g  are disposed within the internal region  12   a , and are connected to a cylindrical wall  12   h  of the mud-gas separator vessel  12 . In several exemplary embodiments, the baffle plates  12   e ,  12   f , and  12   g  are omitted from the mud-gas separator vessel  12 . A manway  12   i  is connected to the cylindrical wall  12   h , and provides access to the internal region  12 . A mud-gas inlet line  20  is in fluid communication with the inlet  12   a  of the mud-gas separator vessel  12 . A gas vent line  22  is in fluid communication with the gas vent  12   b  of the mud-gas separator vessel  12 . A slurry return line  24  is connected to the mud-gas separator vessel  12 , and is in fluid communication with the outlet  12   c . A control valve  26  is in fluid communication with the slurry return line  24 . The electronic controller  16  is connected to, and in communication with, the control valve  26 . In several exemplary embodiments, the electronic controller  16  includes one or more processors, a non-transitory computer readable medium operably coupled to the one or more processors, and a plurality of instructions stored on the non-transitory computer readable medium, the instructions being accessible to, and executable by, the one or more processors. 
     In an exemplary embodiment, the high level alarm  18  is a strobe light high level light/alarm. In an exemplary embodiment, the low level alarm  19  is a strobe light low level light/alarm. 
     In several exemplary embodiments, the guided wave level sensor  14  is, includes, or is part of, a Magnetrol® Eclipse® Model  706  high performance guided wave radar level transmitter, which is available from Magnetrol International, Incorporated, Downers Grove, Ill. USA. 
     In several exemplary embodiments, the electronic controller  16  is, includes, or is part of, a programmable logic controller (PLC). In several exemplary embodiments, the electronic controller  16  is, includes, or is part of, a programmable logic controller from the CP1 family of compact machine controllers, which are available from the Omron Corporation, Tokyo, Japan. 
     In several exemplary embodiments, the control valve  26  is, includes, or is part of, a Fisher® Vee-Ball™ V150, V1200, or V300 rotary control valve, each of which is available from Emerson Process Management, Marshalltown, Iowa USA. 
     In an exemplary embodiment, as illustrated in  FIGS. 2-5  with continuing reference to  FIG. 1 , the mud-gas separator vessel  12  further includes circumferentially-spaced high volume inlets  12   j  and  12   k  at the upper end portion thereof. Parallel-spaced high volume inlet lines  28  and  30  are connected to the mud-gas separator vessel  12 , extending vertically from below the mud-gas separator vessel  12 , along the cylindrical wall  12   h  thereof, and to the upper end portion thereof. The high volume inlet lines  28  and  30  are in fluid communication with the high volume inlets  12   j  and  12   k , respectively. The high volume inlet lines  28  and  30  include valves  28   a  and  30   a , respectively, at lower end portions thereof. A drain outlet  32  is formed through the bottom of the mud-gas separator vessel  12 . A clean-out line  34  is connected to the bottom of the mud-gas separator vessel  12  and is in fluid communication with the drain outlet  32 . The mud-gas separator vessel  12  is mounted on a platform  36 , which is supported by a base frame  38 . The high volume inlet lines  28  and  30  extend through the platform  36 . At least the bottom of the mud-gas separator vessel  12  and the clean-out line  34  extend below the platform  36 . A vertically-extending frame  40  extends upward from the base frame  38  and alongside the mud-gas separator vessel  12 . The vertically-extending frame  40  is connected to at least the cylindrical wall  12   h  of the mud-gas separator vessel  12 . 
     In an exemplary embodiment, as illustrated in  FIG. 6  with continuing reference to  FIGS. 1-5 , the guided wave level sensor  14  includes a guided wave radar probe  14   a . The guided wave radar probe  14   a  extends through the cylindrical wall  12   h  at a location proximate the manway  12   i , and into the internal region  12   d.    
     In an exemplary embodiment, as illustrated in  FIGS. 7 and 8  with continuing reference to  FIGS. 1-6 , the outlet  12   c  of the mud-gas separator vessel  12  includes a horizontally-extending segment  121  extending into the internal region  12   d , a joint  12   m  disposed in the internal region  12   d  and connected to the horizontally-extending segment  121 , and a vertically-extending segment  12   n  disposed in the internal region  12   d  and extending downwards from the joint  12   m . In an exemplary embodiment, the joint  12   m  is a 90-degree, or elbow, fitting. A downward-facing end  12   o  of the vertically-extending segment  12   n  is located near the drain outlet  32 . A fluid passage  12   p  is defined by at least the end  12   o , the vertically-extending segment  12   n , the joint  12   m , and the horizontally-extending segment  121 . The internal region  12   d  is in fluid communication with the slurry return line  24  via at least the fluid passage  12   p . In several exemplary embodiments, the horizontally-extending segment  121 , the joint  12   m , and the vertically-extending segment  12   n  may be characterized as a “dip tube.” 
     A stilling tube  42  extends within the internal region  12   d , from a location near the manway  12   i  to a location near the end  12   o  of the vertically-extending segment  12   n . The guided wave radar probe  14   a  extends within the stilling tube  42 . 
     In operation, in an exemplary embodiment, a multiphase flow travels through the mud-gas inlet line  20 , and into the internal region  12   d  of the mud-gas separator vessel  12  via the inlet  12   a  and/or one or both of the high volume inlet lines  28  and  30 . The multiphase flow traveling through the mud-gas inlet line  20  includes solid, liquid, and gas materials. In several exemplary embodiments, the multiphase flow traveling through the mud-gas inlet line  20  includes drilling fluid (or drilling mud) having free gas therewithin; this drilling mud may be used in oil and gas exploration and production operations. After entering the internal region  12   d , the multiphase flow impinges the baffles  12   e ,  12   f , and  12   g , separating the gas materials from the solid and liquid materials in the multiphase flow. Within the internal region  12   d , gravitational forces also cause the gas materials to separate from the solid and liquid materials in the multiphase flow. The separated gas materials rise upwards and flow out of the mud-gas separator vessel  12  and into the gas vent line  22  via the gas vent  12   b . The remaining solid and liquid materials (hereinafter the “slurry”) collect in the lower end portion of the mud-gas separator vessel  12 , defining a fluid level  44  within the internal region  12   d . Over time, the fluid level  44  rises, and the slurry rises to the end  12   o  and into the portion of the fluid passage  12   p  defined by the vertically-extending segment  12   n . The fluid level  44  continues to rise and, when the fluid level  44  reaches a predetermined level, at least a portion of the slurry is discharged from the mud-gas separator vessel  12 , flowing from the mud-gas separator vessel  12  and into the slurry return line  24  via the outlet  12   c . The slurry flows through the slurry return line  24 , the control valve  26 , and additional flow line(s)  46 , which are part of the slurry return line  24 . 
     During operation, the fluid level  44  is vertically higher than the vertical location of the end  12   o  to prevent any gas materials from exiting the mud-gas separator vessel  12  via the flow passage  12   p  and the outlet  12   c , that is, to prevent “vent gas carry under.” As a result, any risk of fire due to the gas materials is reduced. The slurry within the internal region  12   d  provides a liquid seal that prevents vent gas carry under. During operation, to prevent any gas materials from exiting the mud-gas separator vessel  12  via the flow passage  12   p  and the outlet  12   c , the guided wave level sensor  14  measures the fluid level  44  and communicates data associated with the measurement to the electronic controller  16 . The electronic controller  16 , in turn, automatically controls the control valve  26  based on the measurement data received from the guided wave level sensor  14 . The automatic control of the control valve  26  controls the discharge of the slurry out of the mud-gas separator vessel  12  via the slurry return line  24 . In several exemplary embodiments, based on the measurement data received from the guided wave level sensor  14 , the electronic controller  16 : further opens the control valve  26 , allowing more slurry to flow through the slurry return line  24  and thus reducing the fluid level  44 ; further closes the control valve  26 , reducing the amount of slurry that flows through the slurry return line  24  and thus increasing the fluid level  44 ; or maintains the current valve position of the control valve  26 , the current valve position of the control valve  26  being at a fully open valve position, a fully closed valve position, or a partially open valve position. As a result, the fluid level  44  can be automatically maintained within a predetermined range within the mud-gas separator vessel  12  to prevent vent gas carry under therefrom; the automatic control of the control valve  26  by the electronic controller  16  automatically controls the discharge of the slurry out of the mud-gas separator vessel  12  and thus automatically maintains the fluid level within the predetermined range. 
     During operation, if the controller  16  determines that the fluid level  44  is too high (i.e., is at, or exceeds, a predetermined high level), the controller  16  activates the high level alarm  18 . During operation, if the controller  16  determines that the fluid level  44  is too low (i.e., is at, or is below, another predetermined low level), the controller  16  activates the low level alarm  19 . 
     In several exemplary embodiments, the combination of the guided wave level sensor  14 , the electronic controller  16 , and the control valve  26  provides intelligent system control of slurry discharge from the mud-gas separator vessel  12 , thereby actively preventing vent gas carry under. In several exemplary embodiments, the apparatus  10  maintains the liquid seal provided by the slurry, thereby preventing vent gas carry under. 
     In several exemplary embodiments, due to the intelligent system control, or active control, of the fluid level  44  by the combination of the guided wave level sensor  14 , the electronic controller  16 , and the control valve  26 , the need to include a U-tube in the slurry return line  24  is eliminated, thereby greatly reducing the footprint, and/or the volume, of the apparatus  10  (that is, how much ground space the apparatus  10  takes up, and/or how much volumetric space the apparatus  10  takes up). As a result, the apparatus  10 , or one or more components thereof, are easier to transport and install. 
     In several exemplary embodiments, a vertical distance between the fluid level  44  and the slurry return line  24 , or between the fluid level  44  and the downwardly-facing end  12   o  (or another portion of the segment  121 , the joint  12   m , or the segment  12   n ), must be high enough to reduce the risk of vent gas carry under. As shown in  FIG. 1 , this vertical distance is referred to as mud leg  48 . In several exemplary embodiments, due to the intelligent system control, or active control, of the fluid level  44  in the apparatus  10 , the need to unnecessarily increase the mud leg  48  is eliminated, thereby allowing the mud-gas separator vessel  12  to operate more efficiently and separate more multiphase flow. In several exemplary embodiments, the mud leg  48  may be reduced from, for example, 6 feet to 4 feet. 
     In several exemplary embodiments, instead of, or in addition to one or both of the alarms  18  and  19 , the electronic controller  16  may include a plurality of alarms. In several exemplary embodiments, instead of, or in addition to one or both of the alarms  18  and  19 , the apparatus  10  may include one or more other alarms. 
     In an exemplary embodiment, as illustrated in  FIG. 9  with continuing reference to  FIGS. 1-8 , an apparatus is generally referred to by the reference numeral  50  and includes the great majority of the components of the apparatus  10 , which components are given the same reference numerals. In the apparatus  50  illustrated in  FIG. 9 , the guided wave level sensor  14  is omitted, and the apparatus  50  instead includes a series of level sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e , all of which are operably coupled to the mud-gas separator vessel  12 . In several exemplary embodiments, at least one of the level sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e  includes a vibrating fork level switch. In several exemplary embodiments, at least one of the level sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e  is, includes, or is part of, a Rosemount® 2130 Enhanced Vibrating Fork Liquid Level Switch, which is available from Emerson Process Management Rosemount Inc., Chanhassen, Minn. USA. In several exemplary embodiments, the operation of the apparatus  50  is substantially identical to the operation of the apparatus  10 , except that, instead of the guided wave level sensor  14 , one or more of the level sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e  measure the fluid level  44  and communicate the measurement(s) to the electronic controller  16 . Therefore, the operation of the apparatus  50  will not be described in further detail. 
     In an exemplary embodiment, as illustrated in  FIGS. 10 and 11  with continuing reference to  FIGS. 1-9 , a method of retrofitting a mud-gas separator apparatus  53  (shown in  FIG. 11 ) to reduce the footprint or volume thereof is generally referred to by the reference numeral  54 . As shown in  FIG. 11 , the mud-gas separator apparatus  53  is identical to the mud-gas separator apparatus  50 , except that the additional flow line(s)  46  of the slurry return line  24  of the mud-gas separator apparatus  53  include a U-tube  56 . The U-tube  56  ensures a liquid seal to prevent vent gas carry under from the mud-gas separator vessel  12 , but also significantly increases the footprint or volume of the mud-gas separator apparatus  53 . The method  54  includes: at step  54   a  operably coupling the sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e  to the mud-gas separator vessel  12 ; at step  54   b  operably coupling the electronic controller  16  to the sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e ; at step  54   c  operably coupling the control valve  26  to the electronic controller  16 ; at step  54   e  operably coupling the alarms  18  and  19  to the electronic controller  16 ; and at step  54   f  removing the U-tube  56  from the slurry return line  24 , thereby reducing the footprint or volume of the mud-gas separator apparatus  53 . The U-tube  56  is removed at the step  54   f  because the U-tube  56  is no longer needed to ensure that a liquid seal is maintained to prevent vent gas carry under from the mud-gas separator vessel  12 . The U-tube  56  is no longer needed because of the active control of the liquid level  44  provided by the operation of the combination of the sensors  52   a ,  52   b ,  52   c ,  52   d , and  52   e , the electronic controller  16 , and the control valve  26 . In several exemplary embodiments, the guided wave level sensor  14  may be operably coupled to the mud-gas separator vessel  12  at the step  54   a , and the electronic controller  16  may be operably coupled to the guided wave level sensor  14  at the step  54   b.    
     In an exemplary embodiment, as illustrated in  FIG. 12  with continuing reference to  FIGS. 1-11 , an apparatus is generally referred to by the reference numeral  60  and includes a mud-gas separator vessel  62  and a level sensor housing assembly  64  connected thereto. At least a portion of a guided wave level sensor  66  is housed within the level sensor housing assembly  64 . An electronic controller  68  is operably coupled to, and in communication with, the guided wave level sensor  66 . A control box  70  is connected to the mud-gas separator vessel  62 . At least a portion of the electronic controller  68  is housed within the control box  70 . An electric actuator  72  is operably coupled to, and in communication with, the electronic controller  68 . A control valve  74  is operably coupled to the electric actuator  72 . In several exemplary embodiments, the electric actuator  72  is part of the control valve  74 , and the control valve  74  is in communication with the electronic controller  68  via the electric actuator  72 . As indicated in  FIG. 12  and as will be described in further detail below, in several exemplary embodiments, a multiphase flow is adapted to flow into the mud-gas separator vessel  62 , gas materials are adapted to separate from solid and liquid materials within the mud-gas separator vessel  62 , the separated gas materials are adapted to flow out of the mud-gas separator vessel  62  via a gas vent, and the solid and liquid materials are adapted to flow out of the mud-gas separator vessel  62  and through the control valve  74 . In an exemplary embodiment, the control valve  74  is connected to a slurry return line  75 , and the control valve  74  is in fluid communication with the mud-gas separator vessel  62  via at least the slurry return line  75 . In an exemplary embodiment, the slurry return line  75  is part of the mud-gas separator vessel  62 . As will be described in further detail below, in several exemplary embodiments, the control valve  74  is automatically controlled by the respective operations of the guided wave level sensor  66 , the electronic controller  68 , and the electric actuator  72 . 
     In an exemplary embodiment, as illustrated in  FIGS. 13, 14A, and 14B  with continuing reference to  FIGS. 1-12 , the mud-gas separator  62  includes all of the components of the mud-gas separator  12  as shown in  FIGS. 2-8 , which components are given the same reference numerals. Moreover, the apparatus  60  includes several other components of the apparatus  10  as shown in  FIGS. 1-8 , which components are given the same reference numerals. However, in contrast to the apparatus  10  as shown in  FIGS. 7 and 8 , the apparatus  60  does not include the guided wave level sensor  14  and thus the guided wave radar probe  14   a  thereof does not extend through the cylindrical wall  12   h  of the mud-gas separator vessel  62 . Further, the apparatus  60  does not include the stilling tube  42  and thus the stilling tube  42  does not extend within the internal region  12   d . The guided wave level sensor  14  and the stilling tube  42  are omitted from the apparatus  60  in favor of the guided wave level sensor  66  and the level sensor housing assembly  64 , respectively. 
     In the mud-gas separator vessel  62  shown in  FIGS. 13, 14A, and 14B , the level sensor housing assembly  64  is connected to the exterior of the cylindrical wall  12   h  of the mud-gas separator  62 . The control box  70  is also connected to the exterior of the cylindrical wall  12   h  of the mud-gas separator  62  at a location proximate the manway  12   i  of the mud-gas separator  62 . Although not shown in  FIGS. 13 and 14A , the control valve  74  is in fluid communication with the outlet  12   c  of the mud-gas separator vessel  62 . 
     As shown more clearly in  FIGS. 14A and 14B , the level sensor housing assembly  64  includes a lower t-shaped fitting  76  and an upper t-shaped fitting  78  vertically spaced therefrom. A tubular member  80  is connected to, and extends vertically between, the fittings  76  and  78 . The tubular member  80  is spaced from the exterior of the cylindrical wall  12   h . The tubular member  80  is in fluid communication with each of the fittings  76  and  78 . Isolation valves  82  and  84  are connected to, and in fluid communication with, the fittings  76  and  78 , respectively. The isolation valves  82  and  84  are connected to the cylindrical wall  12   h  of the mud-gas separator vessel  62 , and are in fluid communication with the internal region  12   d  of the mud-gas separator vessel  62  via respective openings (not shown) formed through the cylindrical wall  12   h . The isolation valve  82  is proximate the outlet  12   c , and the isolation valve  84  is proximate the manway  12   i . In an exemplary embodiment, as show in  FIGS. 13 and 14A , the isolation valve  82  is vertically positioned below the outlet  12   c  and thus below the horizontally-extending segment  121 . The tubular member  80  is in fluid communication with the internal region  12   d  of the mud-gas separator vessel  62  via the isolation valves  82  and  84  and the fittings  76  and  78 . The fitting  76  includes a solid cap  86  at the base thereof; in several exemplary embodiments, the cap  86  rests against, or is at least proximate, the platform  36 . The fitting  78  includes a cap  88  at the top thereof. An opening, or insertion port  90  ( FIG. 14A ), is formed through the cap  88 ; a rod-shaped probe  66   a  ( FIG. 14B ) of the guided wave level sensor  66  is adapted to extend through the insertion port  90 . 
     In several exemplary embodiments, instead of being t-shaped, the fittings  76  and  78  may be either y-shaped or cross-shaped, or may have other shapes. In several exemplary embodiments, the tubular member  80  may be integrally formed with one or both of the fittings  76  and  78 . In several exemplary embodiments, the isolation valves  82  and  84  may be integrally formed with the fittings  76  and  78 , respectively. 
     In an exemplary embodiment, the guided wave level sensor  66  is a LevelFlex FMP51 rod-type level sensor, which is available from Endress+Hauser Inc., Greenwood, Ind. USA. In an exemplary embodiment, the guided wave level sensor  66  is connected to the cap  88  of the fitting  78 , and the rod-shaped probe  66   a  ( FIG. 14B ) of the guided wave level sensor  66  extends through the insertion port  90 , through the fitting  78 , and at least within the tubular member  80 . In several exemplary embodiments, the rod-shaped probe  66   a  of the guided wave level sensor  66  extends through the fitting  78 , through the tubular member  80 , and within the fitting  76 . In several exemplary embodiments, the guided wave level sensor  66  is connected to the cap  88  via a flange connection  66   b  ( FIG. 14B ). 
     In an exemplary embodiment, the electronic controller  68  is, includes, or is part of, a CompactRIO embedded system, which is available from National Instruments Corporation, Austin, Tex. USA. In an exemplary embodiment, the electronic controller  68  is, includes, or is part of, a NI Single-Board RIO embedded system, which is available from National Instruments Corporation, Austin, Tex. USA. 
     In an exemplary embodiment, the electric actuator  72  is a Bettis EM-500 Series actuator, which is available from Bettis Electric, Mansfield, Ohio USA. In several exemplary embodiments, the actuator  72  is not an electric actuator and instead is another type of actuator. 
     In an exemplary embodiment, the control valve  74  is a rotary control valve. In an exemplary embodiment, the control valve  74  is a Fisher® Vee-Ball™ V150 rotary control valve, which is available from Emerson Process Management, Marshalltown, Iowa USA. In several exemplary embodiments, the electric actuator  72  is part of the control valve  74 , and/or the components together may be referred to as a control valve that is operably coupled to, and in communication with, the electronic controller  68 . 
     In operation, in an exemplary embodiment, a multiphase flow travels into the internal region  12   d  of the mud-gas separator vessel  62  via the inlet  12   a  and/or one or both of the high volume inlet lines  28  and  30 ; the multiphase flow includes solid, liquid, and gas materials. In several exemplary embodiments, the multiphase flow traveling into the internal region  12   d  includes drilling fluid (or drilling mud) having free gas therewithin; this drilling mud may be used in oil and gas exploration and production operations. After entering the internal region  12   d , the multiphase flow impinges one or more baffles, such as the baffles  12   e ,  12   f , and  12   g , separating the gas materials from the solid and liquid materials in the multiphase flow. Within the internal region  12   d , gravitational forces also cause the gas materials to separate from the solid and liquid materials in the multiphase flow. In several exemplary embodiments, the baffle plates  12   e ,  12   f , and  12   g  are omitted from the mud-gas separator vessel  12 , and the separation of the gas materials from the solid and liquid materials is primarily caused by gravitational forces. 
     The separated gas materials rise upwards and flow out of the mud-gas separator vessel  62  and into the gas vent line  22  via the gas vent  12   b . The remaining solid and liquid materials (hereinafter the “slurry”) collect in the lower end portion of the mud-gas separator vessel  62 , defining the fluid level  44  (shown in  FIGS. 1 and 8 ) within the internal region  12   d . Over time, the fluid level  44  rises, and the slurry rises to the end  12   o  and into the portion of the fluid passage  12   p  defined by the vertically-extending segment  12   n . The fluid level  44  continues to rise and, when the fluid level  44  reaches a predetermined level, at least a portion of the slurry is discharged from the mud-gas separator vessel  12 , flowing out of the mud-gas separator vessel  62  via the outlet  12   c . The slurry subsequently flows through the control valve  74  and additional flow line(s) downstream thereof. 
     During operation, the fluid level  44  is vertically higher than the vertical location of the end  12   o  to prevent any gas materials from exiting the mud-gas separator vessel  62  via the flow passage  12   p  and the outlet  12   c , that is, to prevent “vent gas carry under.” As a result, any risk of fire due to the gas materials is reduced. The slurry within the internal region  12   d  provides a liquid seal that prevents vent gas carry under. During operation, to prevent any gas materials from exiting the mud-gas separator vessel  62  via the flow passage  12   p  and the outlet  12   c , the guided wave level sensor  66  measures the fluid level  44  and communicates data associated with the measurement to the electronic controller  68 . The electronic controller  68  reads the data and, in turn, automatically controls the electric actuator  72 , which opens, further opens, or further closes the control valve  74  based on the measurement data received from the guided wave level sensor  66 ; thus, the electronic controller  68  automatically controls the control valve  74 . The automatic control of the control valve  74  controls the discharge of the slurry out of the mud-gas separator vessel  62 . In several exemplary embodiments, based on the measurement data received from the guided wave level sensor  66 , the electronic controller  68 : opens or further opens the control valve  74 , allowing more slurry to flow out of the internal region  12   d  and thus reducing the fluid level  44 ; further closes the control valve  74 , reducing the amount of slurry that flows out of the internal region  12   d  and thus increasing the fluid level  44 ; or maintains the current valve position of the control valve  74 , the current valve position of the control valve  74  being at a fully open valve position, a fully closed valve position, or a partially open valve position. As a result, the fluid level  44  can be automatically maintained within a predetermined range within the mud-gas separator vessel  62  to prevent vent gas carry under therefrom; the automatic control of the control valve  74  by the electronic controller  68  automatically controls the discharge of the slurry out of the mud-gas separator vessel  62  and thus automatically maintains the fluid level within the predetermined range. In several exemplary embodiments, the predetermined range is based on a desired value for the fluid level  44 , plus an acceptable increase thereabove and minus an acceptable decrease therebelow; thus, the predetermined range extends from a first level, which equals the desired value for the fluid level  44  minus the acceptable decrease therebelow, to a second level, which equals the desired value for the fluid level  44  plus the acceptable increase thereabove. 
     In several exemplary embodiments, the combination of the guided wave level sensor  66 , the electronic controller  68 , the electric actuator  72 , and the control valve  74  provides intelligent system control of slurry discharge from the mud-gas separator vessel  62 , thereby actively controlling the fluid level  44  and actively preventing vent gas carry under. In several exemplary embodiments, the apparatus  60  maintains the liquid seal provided by the slurry, thereby preventing vent gas carry under. 
     In several exemplary embodiments, due to the intelligent system control, or active control, of the fluid level  44  by the combination of the guided wave level sensor  66 , the electronic controller  68 , the electric actuator  72 , and the control valve  74 , the need to include a U-tube downstream of the control valve  74  is eliminated, thereby greatly reducing the footprint, and/or the volume, of the apparatus  60  (that is, how much ground space the apparatus  60  takes up, and/or how much volumetric space the apparatus  60  takes up). As a result, the apparatus  60 , or one or more components thereof, are easier to transport and install. 
     In several exemplary embodiments, the electronic controller  68  may include one or more alarms, and during operation may activate the one or more alarms when the fluid level  44  is too high (i.e., is at, or exceeds, a predetermined high level). In several exemplary embodiments, during operation, the electronic controller  68  may activate one or more alarms when the fluid level  44  is too low (i.e., is at, or is below, another predetermined low level). Instead of, or in addition to, activating one or more alarms, the electronic controller  68  may take other action(s) when the fluid level  44  is too high or too low. 
     In several exemplary embodiments, a vertical distance between the fluid level  44  and the outlet  12   c , or between the fluid level  44  and the downwardly-facing end  12   o  (or another portion of the segment  121 , the joint  12   m , or the segment  12   n ), must be high enough to reduce the risk of vent gas carry under. As shown in  FIGS. 1 and 8 , this vertical distance is referred to as the mud leg  48 . In several exemplary embodiments, due to the intelligent system control, or active control, of the fluid level  44  in the apparatus  60 , the need to unnecessarily increase the mud leg  48  is eliminated, thereby allowing the mud-gas separator vessel  62  to operate more efficiently and separate more multiphase flow, that is, separate gas materials in the multiphase flow from the remaining solid and liquid materials in the multiphase flow. 
     In an exemplary embodiment, as illustrated in  FIG. 15  with continuing reference to  FIGS. 1-14B , a method of controlling the control valve  74 , to actively control the fluid level  44  within the internal region  12   d  (or the mud leg  48  which is based on the fluid level  44 ), is generally referred to by the reference numeral  92 . In several exemplary embodiments, the method  92  is repeatedly executed during the above-described operation of the apparatus  60 . 
     In an exemplary embodiment, the method  92  is executed by the operation of the electronic controller  68 , which is, includes, or is part of, a proportional derivative (PD) controller, as well as by the above-described operation of the guided wave level sensor  66 , the electric actuator  72 , and the control valve  74 . 
     In the method  92 , a proportional parameter P is determined at step  94 . At the step  94 , in an exemplary embodiment, the proportional parameter P is equal to the current fluid level  44 , as currently measured by the guided wave level sensor  66 , minus a set fluid level, which is the desired value for the fluid level  44  (P=Current Fluid Level−Set Fluid Level). At the step  94 , the electronic controller  68  reads data associated with the fluid level  44  from the guided wave level sensor  66 , which transmits the data to the electronic controller  68 . In several exemplary embodiments, the electronic controller  68  reads the data associated with the fluid level  44  from one or more measurements by the guided wave level sensor  66  taken at the end of an update time interval of, for example, every 1 second, 5 seconds, or 10 seconds. 
     At step  96 , a differential parameter D is determined. At the step  96 , in an exemplary embodiment, the differential parameter D is equal to the rate of change of the fluid level  44 . At step  98 , it is determined whether the proportional parameter P is less than a proportional fluctuation constant Pf, and whether the differential parameter D is less than a differential fluctuation constant Df. If it is determined at the step  98  that the proportional parameter P is less than the proportional fluctuation constant Pf, and that the differential parameter D is less than the differential fluctuation constant Df, then at step  100  the change in the valve position of the control valve  74  is set to zero (0) degrees, that is, the valve position of the control valve  74  is not to be changed. If it is determined at the step  98  that the proportional parameter P is not less than the proportional fluctuation constant Pf, and/or that the differential parameter D is not less than the differential fluctuation constant Df, then at step  102  a valve position change Delta is determined. At the step  102 , a valve position change Delta is equal to the product of a proportional constant Pc and the proportional parameter P, plus the product of a differential constant Dc and the differential parameter D (Delta=(Pc)(P)+(Dc)(D)). At step  104 , it is determined whether a rate of change of the valve position due to the valve position change Delta determined at the step  102  would be less than the allowable angular velocity of the valve Vv. If not, then at step  106  the change in the valve position of the control valve  74  is set to the maximum allowable valve position change Delta MAX , which is equal to the product of the allowable angular velocity of the valve Vv and the update time interval between which the data associated with the fluid level  44  is read from the guided wave level sensor  66  (Delta MAX =(Vv)(Update Interval)). If at the step  104  it is determined that the rate of change of the valve position due to the valve position change Delta determined at the step  102  is indeed less than the allowable angular velocity of the valve Vv, then at step  108  the valve position of the control valve  74  is updated by the valve position change Delta determined at the step  102 . Alternatively, if the step  100  was executed, then at the step  108  the valve position of the control valve  74  is updated to remain unchanged, that is, updated by zero degrees. Alternatively, if the step  106  was executed, then at the step  108  the valve position of the control valve  74  is updated by the maximum allowable valve position change Delta MAX  of the control valve  74 . 
     In an exemplary embodiment, at the step  108 , to update the valve position of the control valve  74  by the valve position change Delta determined at the step  102 , the electronic controller  68  sends one or more signals corresponding to the valve position change Delta to the electric actuator  72 , which then opens, further opens, or further closes the control valve  74  by the valve position change Delta (or a value based thereupon). In an exemplary embodiment, at the step  108 , to update the valve position of the control valve  74  by the maximum allowable valve position change Delta MAX  of the control valve  74 , the electronic controller  68  sends one or more signals corresponding to the maximum allowable valve position change Delta MAX  to the electric actuator  72 , which then opens, further opens, or further closes the control valve  74  by the maximum allowable valve position change Delta MAX  (or a value based thereupon). 
     As noted above, in several exemplary embodiments, the method  92  is repeatedly executed during the above-described operation of the apparatus  60 . In an exemplary embodiment, the method  92  is executed upon the reading of data from the guided wave level sensor  66 , the read data being associated with the fluid level  44  measured by the guided wave level sensor  66  at the end of one updated time interval. The execution of the method  92  is then repeated upon the reading of data from the guided wave level sensor  66 , the read data being associated with the fluid level  44  measured by the guided wave level sensor  66  at the end of the next updated time interval; in several exemplary embodiments, this repeated execution of the method  92  continues during the operation of the apparatus  60 . As a result, in several exemplary embodiments, the fluid level  44  is continuously, or nearly continuously, monitored and controlled by the apparatus  60 . 
     As described above, the execution of the method  92  is based on the proportional constant Pc and the differential constant Dc. In an exemplary embodiment, each of the proportional constant Pc and the differential constant Dc is based on at least the diameter of the cylindrical wall  12   h  of the mud-gas separator vessel  62 . In an exemplary embodiment, when the diameter of the cylindrical wall  12   h  is about 6 feet, the proportional constant Pc is 5 or another value, and the differential constant Dc is 15 or another value. In several exemplary embodiments, when the diameter of the cylindrical wall  12   h  is either about 5 feet or about 4 feet, the proportional constant Pc is 5 or another value, and the differential constant Dc is 15 or another value. 
     As described above, the execution of the method  92  is based on the proportional fluctuation constant Pf and the differential fluctuation constant Df. In an exemplary embodiment, the proportional fluctuation constant Pf is about 0.1. In an exemplary embodiment, the differential fluctuation constant Df is about 0.25. In an exemplary embodiment, the proportional fluctuation constant Pf and the differential fluctuation constant Df is about 0.1 and about 0.25, respectively. The execution of the step  98 , and in particular the employment of the proportional fluctuation constant Pf and the differential fluctuation constant Df at the step  98 , prevents the electric actuator  72  from having to make small or otherwise negligible adjustments to the valve position of the control valve  74 , ensuring that only meaningful adjustments to the valve position are made, as necessary, during the above-described operation of the apparatus  60 . 
     As described above, the execution of the method  92  is based on the set fluid level used in the determination at the step  94 , which set fluid level is the desired value for the fluid level  44 . In an exemplary embodiment, the set fluid level used in the determination at the step  94  is based on at least the diameter of the cylindrical wall  12   h  of the mud-gas separator vessel  62 . In an exemplary embodiment, when the diameter of the cylindrical wall  12   h  is about 6 feet, the set fluid level is about 50 inches or another value. In several exemplary embodiments, when the diameter of the cylindrical wall  12   h  is either about 5 feet or about 4 feet, the set fluid level is about 50 inches or another value. 
     In several exemplary embodiments, in addition to the proportional constant Pc, the differential constant Dc, the proportional fluctuation constant Pf, the differential fluctuation constant Df, and the set fluid level, the execution of the method  92  may be based on one or more other parameters including, for example, one or both of the following parameters: the flow rate of the multiphase flow entering the internal region  12   d  in, for example, gallons per minute; and the density of the multiphase flow in, for example, pounds per gallon. 
     In an exemplary embodiment, during the execution of the method  92 , the proportional constant Pc is about 5, the differential constant Dc is about 15, the proportional fluctuation constant Pf is about 0.1, the differential fluctuation constant Df is about 0.25, the diameter of the cylindrical wall  12   h  is about 6 feet, the flow rate of the multiphase flow entering the internal region  12   d  is about 1000 gallons per minute, the set fluid level is about 50 inches, and the density of the multiphase flow is about 16 pounds per gallon. 
     In several exemplary embodiments, the execution of the method  92  during the operation of the apparatus  60  provides intelligent system control, or active control, of the fluid level  44  in the apparatus  60 , thereby eliminating the need to unnecessarily increase the mud leg  48  and allowing the mud-gas separator vessel  62  to operate more efficiently and separate more multiphase flow. 
     In several exemplary embodiments, the execution of the method  92  during the operation of the apparatus  60  permits the mud leg  48  to be within a predetermined range that is generally equal to a vertical height h of the level sensor housing assembly  64  ( FIG. 13 ), thereby allowing the mud-gas separator vessel  62  to operate more efficiently and separate more multiphase flow; to achieve maintaining the mud leg  48  within this predetermined range, the set fluid level used in the determination at the step  94  may be located somewhere along the vertical height h, such as midway along the vertical height h. In several exemplary embodiments, the execution of the method  92  during the operation of the apparatus  60  permits the mud leg  48  to be within a predetermined range that is generally equal to a vertical distance defined by the level sensor housing assembly  64 , such as, for example, the vertical height h of the level sensor housing assembly  64 , the length of the tubular member  80 , the vertical distance between the isolation valves  82  and  84 , or the vertical distance between the fittings  76  and  78 ; to achieve maintaining the mud leg  48  within this predetermined range, the set fluid level used in the determination at the step  94  may be located somewhere along the vertical distance defined by the level sensor housing assembly  64 , such as midway along the vertical distance defined by the level sensor housing assembly  64 . 
     In an exemplary embodiment, during the above-described operation of the apparatus  60  including the above-described execution of the method  92 , the mud-gas separator  62  may experience a “kick” situation, during which an increased amount of gas material flows into the internal region  12   d  of the mud-gas separator  62 . The increased amount of gas material forces more of the slurry (i.e., the solid and liquid materials collected in the mud-gas separator vessel  62 ) to flow out of the internal region  12   d , via the outlet  12   c , and through the control valve  74 , thereby rapidly reducing the fluid level  44  and thus the mud leg  48 . However, the operation of the apparatus  60 , including the execution of the method  92 , automatically responds to the kick situation by accelerating the closing of the control valve  74  to maintain the mud leg  48  in a predetermined range, thereby maintaining the liquid seal that prevents vent gas carry under. In an exemplary embodiment, the predetermined range of the mud leg  48  maintained by the operation of the apparatus  60 , including the execution of the method  92 , is generally equal to a vertical distance defined by the level sensor housing assembly  64 , such as, for example, the vertical height h of the level sensor housing assembly  64 , the length of the tubular member  80 , the vertical distance between the isolation valves  82  and  84 , or the vertical distance between the fittings  76  and  78 . 
     In an exemplary embodiment, during the above-described operation of the apparatus  60  including the above-described execution of the method  92 , the fluid level  44  may begin to rapidly rise, causing the mud leg  48  to rapidly rise. This rapid rise in the fluid level  44 , and thus the mud leg  48 , may occur due to one or more reasons such as, for example, flow blockage or a clog in a fluid line located downstream of the control valve  74 , or a rapid increase in the flow rate of the multiphase flow traveling into the internal region  12   d . However, the operation of the apparatus  60 , including the execution of the method  92 , automatically responds to the rapid rise of the fluid level  44  by accelerating the opening of the control valve  74  to maintain the mud leg  48  in a predetermined range, thereby maintaining the separation performance of the mud-gas separator vessel  62 . In an exemplary embodiment, the predetermined range of the mud leg  48  maintained by the operation of the apparatus  60 , including the execution of the method  92 , is generally equal to a vertical distance defined by the level sensor housing assembly  64 , such as, for example, the vertical height h of the level sensor housing assembly  64 , the length of the tubular member  80 , the vertical distance between the isolation valves  82  and  84 , or the vertical distance between the fittings  76  and  78 . 
     In several exemplary embodiments, the method  92  may be employed to automatically control the control valve  26  in a manner substantially similar to the above-described manner by which the method  92  is employed to automatically control the control valve  74 . 
     In an exemplary experimental embodiment,  FIG. 16  illustrates a user interface  110  displayed on at least a portion of a display screen. In several exemplary experimental embodiments, the user interface  110  is part of a simulation program developed to fine tune and verify the performance of the algorithm employed in the method  92  of  FIG. 15 . In several exemplary experimental embodiments, the real-life behavior of an exemplary embodiment of the control valve  74  was modeled and embedded into the simulation program of which the user interface  110  is a part. As shown in  FIG. 16 , the user interface  110  includes an output  112  and input fields  114 ,  116 ,  118 ,  120 ,  122 ,  124 ,  126 ,  128 ,  130 ,  132 , and  134 . The proportional constant Pc is inputted in the field  114 . The differential constant Dc is inputted in the field  116 . The diameter of the cylindrical wall  12   h  is inputted in the field  118 . The flow rate of the multiphase flow entering the internal region  12   d  is inputted in the field  120 . The set fluid level to be used in the determination at the step  94  is inputted in the field  122 ; this set fluid level is the desired value for the fluid level  44 . The density of the multiphase flow entering the internal region  12   d  is inputted in the field  124 . In several exemplary embodiments, at least for the purpose of executing the simulation program of which the user interface  110  is a part, the initial height of the fluid level  44  is inputted in the field  126 , the initial open percentage of the control valve  74  (the initial degree to which the control valve  74  is open) is inputted in the field  128  (0% if the valve  74  is completely closed, 100% if the valve  74  is completely open), a kick situation pressure is inputted in the field  130 , and the kick situation duration is inputted in the field  132 . 
     As shown in  FIG. 16 , the output  112  includes a chart  134 . The chart  134  includes a horizontal axis  136  that indicates duration of time in, for example, seconds. In several exemplary embodiments, the duration of time indicated by the horizontal axis  136  represents the duration of time of operation of the apparatus  60 , or at least the duration of time of the repeated execution of the method  92 . The chart  134  further includes on either side thereof parallel-spaced vertical axes  138  and  140 . The vertical axis  138  indicates the fluid level  44  in, for example, inches. The vertical axis  140  indicates the open position of the control valve  74  in, for example, degrees (0 degrees if the valve  74  is completely closed, 100 degrees if the valve  74  is completely open). 
     The chart  134  displays five data series, namely data series  142 ,  144 ,  146 ,  148 , and  150 . The data series  142  indicates a value of the fluid level  44  necessary to provide a minimum fluid seal. The data series  142  is a horizontal line, indicating that the minimum fluid seal is constant across the duration of time. In an exemplary embodiment, the fluid level  44  necessary to provide a minimum fluid seal is located slightly above, or is slightly higher than the vertical position of, the downward-facing end  12   o  of the vertically-extending segment  12   n  that is located near the drain outlet  32 ; this vertical location is referred to by the reference numeral  44   a  in  FIG. 8 . 
     The data series  144  indicates a value of the fluid level  44  necessary to provide a conservatively safe fluid seal. The data series  144  is a horizontal line, indicating that the conservative safe fluid seal is constant across the duration of time. In an exemplary embodiment, the fluid level  44  necessary to provide the conservatively safe fluid seal is located along the nominal center line of the horizontally-extending segment  121 ; this vertical location is referred to by the reference numeral  44   b  in  FIG. 8 . 
     The data series  146  indicates the set fluid level used in the determination at the step  94 ; this set fluid level is the desired value for the fluid level  44 . The data series  146  is a horizontal line, indicating that the set fluid level used in the determination at the step  94  is constant across the duration of time. In an exemplary embodiment, the set fluid level used in the determination at the step  94  is located above, or is higher than the vertical position of, the vertical location  44   b ; this vertical location of the set fluid level is referred to by the reference  44   c  in  FIG. 8 . 
     The data series  148  indicates the actual fluid level  44 , as measured by the guide wave level sensor  66 . The data series  148  is not horizontal, but changes over time, indicating that the actual fluid level  44  varies over time. In an exemplary experimental embodiment, the vertical location of the actual fluid level  44  at a time of 1 second, as indicated by the chart  134  in the  FIG. 16 , is referred to by the reference numeral  44   d  in  FIG. 8 . 
     The data series  150  indicates the degree to which the control valve  74  is open. The data series  150  is not horizontal, but changes over time, indicating that the degree to which the control valve  74  is open varies over time. 
     As shown in  FIG. 16 , in an exemplary experimental embodiment, at a time of 1 second, the actual fluid level  44  indicated by the data series  148  is above the set fluid level indicated by the data series  146 , potentially reducing the separation performance of the mud-gas separator vessel  62 . However, the apparatus  60 , due to the execution of the method  92 , automatically detects this relatively high fluid level  44  and automatically responds to the relatively high fluid level  44  by accelerating the opening of the control valve  74  to a partially open valve position above 80 degrees, maintaining this partially open valve position for a period of time (until an elapsed time of about 21 seconds), and then automatically closing the control valve  74  to a partially open valve position of about 80 degrees, and subsequently to less than 80 degrees, when the actual fluid level  44  indicated by the data series  148  is about equal to the set fluid level indicated by the data series  146 . 
     As shown in  FIG. 17 , in an exemplary experimental embodiment, at a time of 1 second, the actual fluid level  44  indicated by the data series  148  is below the set fluid level indicated by the data series  146 , potentially increasing the risk of breaking the liquid seal provided by the slurry collected in the internal region  12   d . However, the apparatus  60 , due to the execution of the method  92 , automatically detects this relatively low fluid level  44  and automatically responds to the relatively low fluid level  44  by accelerating the closing of the control valve  74  to a completely or fully closed valve position, maintaining this completely or fully closed valve position for a period of time (until an elapsed time of about 23-26 seconds), automatically opening the control valve  74  to a partially open valve position of about 80 degrees, and then automatically closing the control valve  74  to a partially open valve position of about 60 degrees, or slightly higher than 60 degrees, when the actual fluid level  44  indicated by the data series  148  is about equal to the set fluid level indicated by the data series  146 . 
     Although  FIG. 16  illustrates an exemplary experimental embodiment of the user interface  110  that is part of a simulation program developed to fine tune and verify the performance of the algorithm employed in the method  92  of  FIG. 15 , in several exemplary embodiments, the method  92  includes displaying an output on a display screen that is similar to the embodiment of the output  112  shown in  FIG. 16 , that is, when the fluid level  44  is rapidly rising and the apparatus  60  automatically responds by accelerating the opening of the control valve  74 ; in several exemplary embodiments, the electronic controller  68 , and/or another computing device in communication with the electronic controller  68 , is programmed to display this similar output during the execution of the method  92 . 
     Similarly, although  FIG. 17  illustrates an exemplary experimental embodiment of the user interface  110  that is part of a simulation program developed to fine tune and verify the performance of the algorithm employed in the method  92  of  FIG. 15 , in several exemplary embodiments, the method  92  includes displaying an output on a display screen that is similar to the embodiment of the output  112  shown in  FIG. 17 , that is, when the fluid level  44  is rapidly decreasing and the apparatus  60  automatically responds by accelerating the closing of the control valve  74 ; in several exemplary embodiments, the electronic controller  68 , and/or another computing device in communication with the electronic controller  68 , is programmed to display this similar output during the execution of the method  92 . 
     In several exemplary embodiments, the electronic controller  68  includes one or more processors, a non-transitory computer readable medium operably coupled to the one or more processors, and a plurality of instructions (or computer program(s)) stored on the non-transitory computer readable medium, the instructions or program(s) being accessible to, and executable by, the one or more processors; in several exemplary embodiments, the one or more processors of the electronic controller  68  execute the plurality of instructions (or computer program(s)) to repeatedly execute at least the method  92  during the operation of the apparatus  60 . 
     In an exemplary embodiment, as illustrated in  FIG. 18  with continuing reference to  FIGS. 1-17 , the apparatus  60  includes a computing device  152  in communication with the electronic controller  68  via a network  154 . The computing device  152  includes a display  156  on which output  158  is configured to be displayed, the output  158  being similar to the output  112  except that the respective data series displayed on the output  158  (which are equivalent to the data series  142 ,  144 ,  146 ,  148 , and  150 ) indicate the different fluid levels and the valve position of the control valve  74  during the actual operation of the apparatus  60  (rather than a simulation). In an exemplary embodiment, the computing device  152  is located at the site at which the mud-gas separator vessel  62  is located. In an exemplary embodiment, the computing device  152  is remotely located from the mud-gas separator vessel  62 . As a result, the computing device  152  permits the apparatus  60  to be remotely monitored. In an exemplary embodiment, the computing device  152  is a part of the electronic controller  68 . 
     In an exemplary embodiment, the computing device  152  executes a program having a user interface that is similar to the user interface  110 , except that the respective input fields that are part of the user interface executed on the computing device  152  (which are equivalent to at least the fields  114 - 124 ) are used to modify the automatic operation the apparatus  60  (rather than a simulation), and the respective data series displayed on the output  158  (which are equivalent to the data series  142 ,  144 ,  146 ,  148 , and  150 ) indicate the different fluid levels and the valve position of the control valve  74  during the actual operation of the apparatus  60  (rather than a simulation). In an exemplary embodiment, the computing device  152  is located at the site at which the mud-gas separator vessel  62  is located. In an exemplary embodiment, the computing device  152  is remotely located from the mud-gas separator vessel  62 . As a result, the computing device  152  permits the apparatus  60  to be remotely monitored, and further permits the operation of the apparatus  60  to be remotely modified by inputting one or more different values in one or more of the respective input fields that are equivalent to at least the fields  114 - 124 . 
     In an exemplary embodiment, as illustrated in  FIG. 19  with continuing reference to  FIGS. 1-18 , a method of retrofitting a mud-gas separator apparatus is generally referred to by the reference numeral  160  and includes steps  162 ,  164 ,  166 , and  168 . At the step  162 , the guided wave level sensor  66  is coupled to a mud-gas separator vessel. In an exemplary embodiment, the step  162  includes connecting the guided wave level sensor  66  to the level sensor housing assembly  64  in accordance with the foregoing, and connecting the level sensor housing  64  to the mud-gas separator vessel. At the step  164 , the electronic controller  64  is operably coupled to the guided wave level sensor  66 . At the step  166 , the control valve  74  is operably coupled to the electronic controller  64 . In an exemplary embodiment, the step  166  includes operably coupling the electric actuator  72  to the control valve  74 , and operably coupling the electric actuator  72  to the electronic controller  68  so that the control valve  74  is operably coupled to the electronic controller  68  via the electric actuator  72 . At the step  168 , the control valve  74  is connected to the slurry return line  75 . 
     In an exemplary embodiment, as illustrated in  FIG. 20  with continuing reference to  FIGS. 1-19 , a method of controlling the control valve  74 , to actively control the fluid level  44  within the internal region  12   d  (or the mud leg  48  which is based on the fluid level  44 ), is generally referred to by the reference numeral  170 . In several exemplary embodiments, the method  170  is repeatedly executed during the above-described operation of the apparatus  60 . 
     In an exemplary embodiment, the method  170  is executed by the operation of the electronic controller  68 , which is, includes, or is part of, a proportional derivative (PD) controller, as well as by the above-described operation of the guided wave level sensor  66 , the electric actuator  72 , and the control valve  74 . 
     The method  170  includes all of the steps of the method  92 , which steps are given the same reference numerals. The method  170  further includes a step  172 , which in an exemplary embodiment is executed after the step  96  but before the step  98 . At the step  172 , it is determined whether the fluid level  44  is within a stability zone. If so, then the step  100  is executed. If it is determined at the step  172  that the fluid level is not within the stability zone, then the step  98  is executed. Except for the execution of the step  172 , the execution of the method  170  is identical to the above-described execution of the method  92 ; therefore, the remainder of the execution of the method  170  will not be described in detail. 
     In several exemplary embodiments, the step  172  is executed before one or both of the steps  94  and  96 . In several exemplary embodiments, the step  172  is executed after the step  98 . 
     In an exemplary embodiment, as illustrated in  FIG. 21  with continuing reference to  FIGS. 1-20 , the step  172  of the method  170  includes steps  172   a  and  172   b . At the step  172   a , it is determined whether the fluid level  44  is greater than about a first predetermined level (or a lower boundary fluid level). If it is determined at the step  172   a  that the fluid level  44  is not greater than about the first predetermined level, then it is determined that the fluid level  44  is not within the stability zone and the step  98  is executed. If it is determined at the step  172   a  that the fluid level  44  is greater than about the first predetermined level, then the step  172   b  is executed. At the step  172   b , it is determined whether the fluid level  44  is less than about a second predetermined level (or an upper boundary fluid level). If so, then the fluid level  44  is determined to be within the stability zone that is defined between the first and second predetermined fluid levels employed at the steps  172   a  and  172   b , respectively. Since the fluid level  44  is within the stability zone, the step  100  executed and thus the change in the valve position of the control valve  74  is set to zero (0) degrees, that is, the valve position of the control valve  74  is not to be changed. If it is determined at the step  172   b  that the fluid level  44  is above about the second predetermined level, then it is determined that the fluid level  44  is not within the stability zone and the step  98  is executed. 
     In an exemplary embodiment, the first predetermined level employed at the step  172   a  is the vertical location indicated by the reference numeral  44   b  in  FIG. 8 , or another vertical location. In an exemplary embodiment, the second predetermined level employed at the step  172   b  is the vertical location indicated by the reference numeral  44   d  in  FIG. 8 , or another vertical location. In an exemplary embodiment, the first and second predetermined levels employed at the steps  172   a  and  172   b , respectively, are the vertical locations indicated by the reference numerals  44   c  and  44   d , respectively. 
     In an exemplary embodiment, the execution of the method  170 , and in particular the execution of the step  172  of the method  170 , greatly reduces the duty cycle of the electric actuator  72 . As a result, the useful operating lives of the electric actuator  72  and the control valve  74  are greatly prolonged. 
     In an exemplary embodiment, the execution of the method  170 , and in particular the execution of the step  172  of the method  170 , results in little or no change to the valve position of the control valve  74  so long as the flow rate of the multiphase flow traveling into the internal region  12   d  is generally constant. As a result, the useful operating lives of the electric actuator  72  and the control valve  74  are greatly prolonged. 
     In several exemplary embodiments, the method  170  may be employed to automatically control the control valve  26  in a manner substantially similar to the above-described manner by which the method  170  is employed to automatically control the control valve  74 . 
     In an exemplary experimental embodiment, as illustrated in  FIG. 22  with continuing reference to  FIGS. 1-21 , experimental testing was conducted using an exemplary experimental embodiment of the apparatus  60 . During the experimental testing, the experimental exemplary embodiment of the apparatus  60  was operated in accordance with the above-described operation of the apparatus  60 , and an experimental exemplary embodiment of the method  170  was executed during this operation.  FIG. 22  includes a chart  174  describing the automatic response of the experimental embodiment of the apparatus  60  when the flow rate of the fluid traveling into the internal region  12   d  was quickly increased from about 160 gpm to about 420 gpm, as indicated by a data series  176  in the chart  174 . The fluid level  44  over time is indicated by a data series  178 . As shown in the chart  174 , the mud-gas separator vessel  62  includes a stability zone  180 . The stability zone  180  has a lower boundary fluid level  182 , which is equal to the first predetermined level employed at the step  172   a . The stability zone  180  also has an upper boundary fluid level  184 , which is equal to the second predetermined level employed at the step  172   b . The stability zone  180  extends between the fluid levels  182  and  184 , and is unchanged over time. As shown in the chart  174 , the lower boundary fluid level  182  was about 30 inches above the downward-facing end  12   o  of the vertically-extending segment  12   n , and the upper boundary fluid level  184  was about 46 inches above the downward-facing end  12   o.    
     As shown in the chart  174 , in an exemplary experimental embodiment, at an initial flow rate of 160 gpm, the fluid level  44  within the mud-gas separator vessel  62  was within the stability zone  180 , as indicated by the data series  178  from 0 to about 24 seconds. Beginning at about a time of 24 seconds, the flow rate was quickly increased from about 160 gpm to about 420 gpm at a time of about 30 seconds, causing the fluid level  44  to rise above the upper boundary fluid level  184  at around 40 seconds, outside of (or not within) the stability zone  180 . In response, the automatic operation of the exemplary experimental embodiment of the apparatus  60 , including the automatic execution of the exemplary experimental embodiment of the method  170 , caused the fluid level  44  to drop to about 25 inches at about a time of 58 seconds, and then rise to a steady state fluid level  44  of about 42 inches at about a time of 120 seconds. This steady state fluid level  44  was within the stability zone  180 . In an exemplary experimental embodiment, as shown in  FIG. 22 , the exemplary experimental embodiment of the apparatus  60  was able to stabilize in about 90 seconds in response to the quick increase of the flow rate from about 160 gpm to about 420 gpm, that is, the fluid level  44  was able to return to the stability zone  180  in about 90 seconds after the flow rate was increased to about 420 gpm. 
     In an exemplary embodiment, as illustrated in  FIG. 23  with continuing reference to  FIGS. 1-22 , a chart  186  describes the response of the experimental embodiment of the apparatus  60  when the flow rate of the fluid traveling into the internal region  12   d  was quickly decreased from about 420 gpm to about 160 gpm, as indicated by the data series  176  in the chart  186 . As shown in the chart  186 , at an initial flow rate of 420 gpm, the fluid level  44  within the mud-gas separator vessel  62  was within the stability zone  180 , as indicated by the data series  178  from 0 to about 16 seconds. Beginning at a time of about 16 seconds, the flow rate was quickly decreased from about 420 gpm to about 160 gpm at a time of about 24 seconds, causing the fluid level  44  to drop below the lower boundary fluid level  182  at around 40 seconds, outside of the stability zone  180 . In response, the automatic operation of the exemplary experimental embodiment of the apparatus  60 , including the automatic execution of the exemplary experimental embodiment of the method  170 , caused the fluid level  44  to increase to a steady state fluid level  44  of about 31 inches at about a time of 76 seconds. This steady state fluid level  44  was within the stability zone  180 . In an exemplary experimental embodiment, as shown in  FIG. 23 , the exemplary experimental embodiment of the apparatus  60  was able to stabilize in about 52 seconds in response to the quick decrease of the flow rate from about 420 gpm to about 160 gpm, that is, the fluid level  44  was able to return to the stability zone  180  in about 52 seconds after the flow rate was decreased to about 160 gpm. 
     In an exemplary embodiment, as illustrated in  FIG. 24  with continuing reference to  FIGS. 1-23 , a chart  188  describes the response of the experimental embodiment of the apparatus  60  when the apparatus  60  was subjected to a disturbance in which the flow rate of the fluid traveling into the internal region  12   d  was quickly increased from about 160 gpm to about 530 gpm, held at about 530 gpm for about 10-15 seconds, and then quickly decreased back down to about 160 gpm, as indicated by the data series  176  in the chart  188 . As shown in the chart  188 , at an initial flow rate of 160 gpm, the fluid level  44  within the mud-gas separator vessel  62  was within the stability zone  180 , as indicated by the data series  178  from 0 to about 85 seconds. Beginning at a time of about 80 seconds, the flow rate was quickly increased from about 160 gpm to about 530 gpm at about a time of 85 seconds, causing the fluid level  44  to rise above the upper boundary fluid level  184  slightly thereafter, outside of the stability zone  180 . The flow rate was held at about 530 gpm for about 10-15 seconds, and then was quickly decreased back down to about 160 gpm, causing a disturbance, or temporary spike, in the flow rate. In response to the disturbance, or temporary spike, in the flow rate, the automatic operation of the exemplary experimental embodiment of the apparatus  60 , including the automatic execution of the exemplary experimental embodiment of the method  170 , caused the fluid level  44  to drop to about 20 inches at about a time of 110 seconds, and then rise to a steady state fluid level  44  of about 35 inches at about a time of 200 seconds or slightly past 200 seconds (e.g., 205 seconds). This steady state fluid level  44  was within the stability zone  180 . In an exemplary experimental embodiment, as shown in  FIG. 22 , the exemplary experimental embodiment of the apparatus  60  was able to stabilize in about 120 seconds in response to the disturbance in the flow rate, that is, the fluid level  44  was able to return to the stability zone  180  in about 120 seconds after the disturbance, or temporary spike, in the flow rate. 
     In several exemplary embodiments, a plurality of instructions, or computer program(s), are stored on a non-transitory computer readable medium, the instructions or computer program(s) being accessible to, and executable by, one or more processors. In several exemplary embodiments, the one or more processors execute the plurality of instructions (or computer program(s)) to repeatedly execute at least the method  92 , or at least the method  170 , during the operation of the apparatus  60 . In several exemplary embodiments, the one or more processors are part of the electronic controller  68 , the computing device  152 , one or more other computing devices, or any combination thereof. In several exemplary embodiments, the non-transitory computer readable medium is part of the electronic controller  68 , the computing device  152 , one or more other computing devices, or any combination thereof. 
     In an exemplary embodiment, as illustrated in  FIG. 25  with continuing reference to  FIGS. 1-24 , an illustrative node  1000  for implementing one or more embodiments of one or more of the above-described networks, elements, methods and/or steps, and/or any combination thereof, is depicted. The node  1000  includes a microprocessor  1000   a , an input device  1000   b , a storage device  1000   c , a video controller  1000   d , a system memory  1000   e , a display  1000   f , and a communication device  1000   g  all interconnected by one or more buses  1000   h . In several exemplary embodiments, the storage device  1000   c  may include a floppy drive, hard drive, CD-ROM, optical drive, any other form of storage device and/or any combination thereof. In several exemplary embodiments, the storage device  1000   c  may include, and/or be capable of receiving, a floppy disk, CD-ROM, DVD-ROM, or any other form of computer-readable medium that may contain executable instructions. In several exemplary embodiments, the communication device  1000   g  may include a modem, network card, or any other device to enable the node to communicate with other nodes. In several exemplary embodiments, any node represents a plurality of interconnected (whether by intranet or Internet) computer systems, including without limitation, personal computers, mainframes, PDAs, smartphones and cell phones. 
     In several exemplary embodiments, one or more of the components of the apparatus  10 ,  50 ,  52 , or  60 , such as one or more of the sensors  14 ,  52   a ,  52   b ,  52   c ,  52   d , and  52   e , the electronic controller  16 , the control valve  26 , the guided wave level sensor  66 , the electronic controller  68 , the electric actuator  72 , the control valve  74 , and the computing device  152 , include at least the node  1000  and/or components thereof, and/or one or more nodes that are substantially similar to the node  1000  and/or components thereof. In several exemplary embodiments, one or more of the above-described components of the node  1000  and/or the apparatus  10 ,  50 ,  53 , or  60 , include respective pluralities of same components. 
     In several exemplary embodiments, a computer system typically includes at least hardware capable of executing machine readable instructions, as well as the software for executing acts (typically machine-readable instructions) that produce a desired result. In several exemplary embodiments, a computer system may include hybrids of hardware and software, as well as computer sub-systems. 
     In several exemplary embodiments, hardware generally includes at least processor-capable platforms, such as client-machines (also known as personal computers or servers), and hand-held processing devices (such as smart phones, tablet computers, personal digital assistants (PDAs), or personal computing devices (PCDs), for example). In several exemplary embodiments, hardware may include any physical device that is capable of storing machine-readable instructions, such as memory or other data storage devices. In several exemplary embodiments, other forms of hardware include hardware sub-systems, including transfer devices such as modems, modem cards, ports, and port cards, for example. 
     In several exemplary embodiments, software includes any machine code stored in any memory medium, such as RAM or ROM, and machine code stored on other devices (such as floppy disks, flash memory, or a CD ROM, for example). In several exemplary embodiments, software may include source or object code. In several exemplary embodiments, software encompasses any set of instructions capable of being executed on a node such as, for example, on a client machine or server. 
     In several exemplary embodiments, combinations of software and hardware could also be used for providing enhanced functionality and performance for certain embodiments of the present disclosure. In an exemplary embodiment, software functions may be directly manufactured into a silicon chip. Accordingly, it should be understood that combinations of hardware and software are also included within the definition of a computer system and are thus envisioned by the present disclosure as possible equivalent structures and equivalent methods. 
     In several exemplary embodiments, computer readable mediums include, for example, passive data storage, such as a random access memory (RAM) as well as semi-permanent data storage such as a compact disk read only memory (CD-ROM). One or more exemplary embodiments of the present disclosure may be embodied in the RAM of a computer to transform a standard computer into a new specific computing machine. In several exemplary embodiments, data structures are defined organizations of data that may enable an embodiment of the present disclosure. In an exemplary embodiment, a data structure may provide an organization of data, or an organization of executable code. 
     In several exemplary embodiments, any networks and/or one or more portions thereof, may be designed to work on any specific architecture. In an exemplary embodiment, one or more portions of any networks may be executed on a single computer, local area networks, client-server networks, wide area networks, internets, hand-held and other portable and wireless devices and networks. 
     In several exemplary embodiments, a database may be any standard or proprietary database software. In several exemplary embodiments, the database may have fields, records, data, and other database elements that may be associated through database specific software. In several exemplary embodiments, data may be mapped. In several exemplary embodiments, mapping is the process of associating one data entry with another data entry. In an exemplary embodiment, the data contained in the location of a character file can be mapped to a field in a second table. In several exemplary embodiments, the physical location of the database is not limiting, and the database may be distributed. In an exemplary embodiment, the database may exist remotely from the server, and run on a separate platform. In an exemplary embodiment, the database may be accessible across the Internet. In several exemplary embodiments, more than one database may be implemented. 
     In several exemplary embodiments, a plurality of instructions stored on a computer readable medium may be executed by one or more processors to cause the one or more processors to carry out or implement in whole or in part the above-described operation of each of the above-described exemplary embodiments of the mud-gas separator apparatus  10 ,  50 ,  53 , or  60 , the method  54 , the method  92 , the method  170 , and/or any combination thereof. In several exemplary embodiments, such a processor may include one or more of the microprocessor  1000   a , any processor(s) that are part of the components of the mud-gas separator apparatus  10 ,  50 ,  53 , or  60 , and/or any combination thereof, and such a computer readable medium may be distributed among one or more components of the mud-gas separator apparatus  10 ,  50 ,  53 , or  60 . In several exemplary embodiments, such a processor may execute the plurality of instructions in connection with a virtual computer system. In several exemplary embodiments, such a plurality of instructions may communicate directly with the one or more processors, and/or may interact with one or more operating systems, middleware, firmware, other applications, and/or any combination thereof, to cause the one or more processors to execute the instructions. 
     In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “left” and right”, “front” and “rear”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms. 
     In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear. 
     In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive. 
     Furthermore, invention(s) have described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.