Patent Publication Number: US-2017355534-A1

Title: Dry bulk pneumatic metering assembly and method

Description:
BACKGROUND 
     In the drilling and completion industry, the formation of boreholes for the purpose of production or injection of fluid is common. The boreholes are used for exploration or extraction of natural resources such as hydrocarbons, oil, gas, water, and alternatively for CO2 sequestration. To increase the production from a borehole, the production zone can be fractured to allow the formation fluids to flow more freely from the formation to the borehole. The fracturing operation includes pumping fluids at high pressure towards the formation wall to form formation fractures. To retain the fractures in an open condition after fracturing pressure is removed, the fractures must be physically propped open, and therefore the fracturing fluids commonly include solid granular materials, such as sand, generally referred to as proppants. Due to the large amount of fracturing fluid required for some operations, a correspondingly large amount of proppants are required which must be metered out in appropriate quantities to the frac blenders. 
     One prior method of measuring bulk material flow rate includes using a calibrated screw which moves a known weight per revolution, and then measuring the screw which drops dry products down into a chamber. Another prior method allows dry product to fall by gravity and then counts the particles and calculates the known rate of fall by the particles to calculate rate. 
     The art would be receptive to alternative systems and methods for determining bulk material flow rate. 
     BRIEF DESCRIPTION 
     A dry bulk pneumatic metering system includes a flow line configured for the passage of pneumatically-conveyed bulk material, a bulk material sensor arranged relative to the flow line, the bulk material sensor configured to send a first signal related to a quantity of the bulk material passing in the flow line and within a range of the bulk material sensor, a speed sensor arranged with respect to at least one area of the system, the speed sensor configured to send a second signal related to the speed of gas flow at the at least one area of the system, and a controller arranged to receive the first and second signals and configured to calculate a bulk material flow rate of the bulk material using the first and second signals. 
     An operating system including: a material receiving member; and, the dry bulk pneumatic metering system of claim  1 , the dry bulk pneumatic metering system further including a discharge portion arranged to discharge the bulk material from the dry bulk pneumatic metering system; wherein the bulk material discharged from the dry bulk pneumatic metering system is delivered to the material receiving member. 
     A method of determining a bulk material flow rate in a dry bulk pneumatic metering system, the method including: pneumatically conveying bulk material through a flow line of the system; sensing a quantity of the bulk material passing within the flow line and within a range of a bulk material sensor, the bulk material sensor arranged relative to the flow line, the bulk material sensor sending a first signal to a controller of the system; sensing a speed of gas flow at at least one area of the system using a speed sensor, the speed sensor sending a second signal to the controller; and, using the first and second signals in the controller to calculate the bulk material flow rate of the bulk material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  depicts a schematic diagram of one embodiment of a dry bulk pneumatic flow rate determining system; 
         FIG. 2  depicts a process flow diagram of one embodiment of an assembly incorporating the system of  FIG. 1 ; 
         FIG. 3  depicts a schematic diagram of the assembly of  FIG. 2 ; and, 
         FIG. 4  depicts a schematic view of an embodiment of an operational system usable for a downhole fracturing operation at a wellsite. 
     
    
    
     DETAILED DESCRIPTION 
     A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
     One embodiment of a dry bulk pneumatic metering system  10  for determining flow rate of a pneumatically conveyed bulk material  12  is shown in  FIG. 1 . The material  12  may be any dry, solid, particulate material, such as, but not limited to, sand and other proppants, salt, seed, shells, dust, powders, and additives, capable of being pneumatically conveyed through a flow line  14 , such as a pipe or tube. In one embodiment, a blower  16  may be used to pneumatically convey the material  12  in flow direction  18 , however the blower need not be directly connected to the flow line  14 . For example, the blower  16  may pressurize a tank (as shown in  FIGS. 2 and 3 ) containing a source of the material  12 , which in turn selectively releases the material  12  into the flow line  14 . The system  10  includes at least two sensors  20 ,  22  including at least one bulk material sensor  20  and at least one gas speed sensor  22 . In the illustrated embodiment, a first bulk material sensor  20  and a first gas speed sensor  22  are configured to sense an interior  24  of the flow line  14 , which may be pneumatically pressurized. However, in an alternative embodiment, the first gas speed sensor  22  or other gas speed sensors  22  may be positioned to detect gas speed within the system  10  at an area of the system  10  that does not pass the material  12 . That is, the gas speed sensor  22  may alternatively be positioned on a “clean” side of the system  10  (a portion of the system  10  through which the material  12  does not pass) while the bulk material sensor  20  is positioned on a “dirty” side of the system  10  (a portion of the system  10  through which the material  12  passes). While the gas speed sensor  22  may be positioned on the clean side of the system  10 , the bulk material sensor  20  must be positioned on the dirty side of the system  10 . Further, while the illustrated embodiment of the system  10  depicts the gas speed sensor  22  arranged to detect gas speed in the flow line  14  at a point downstream of the bulk material sensor  20 , the gas speed sensor  22  may alternatively be positioned to detect gas speed in the flow line  14  at a point upstream of the bulk material sensor  20 . 
     One embodiment of the bulk material sensor  20  for detecting a quantity of material  12  in the flow line  14 , and that can detect an amount of dry bulk material  12  in a void, is schematically depicted in  FIG. 1 . The bulk material sensor  20  may be a Doppler radar sensor that emits a sensor signal (electromagnetic waves, such as radio waves or microwaves), and the back-reflected Doppler-shifted energy signal is detected by the sensor  20  as the material  12  moves through the range  26  of the sensor  20  and is contacted by the sensor signal. The bulk material sensor  20  may alternatively be an optical sensor that can detect reflected light from the passing material  12 , in which case the optical sensor may additionally include a light source for directing a light signal onto the passing material  12 . Other commercially available bulk material sensors that are capable of measuring the quantity of particles in a void, such as a percentage of particles of material within the fluid (air) in the flow line  14  may also be incorporated into the system  10 . In the illustrated embodiment, the bulk material sensor  20  includes an attachment section  28  for attaching the bulk material sensor  20  to the flow line  14 . The attachment section  28  may include threads as shown, which are engageable with a threaded opening in the flow line  14 . Alternatively, the attachment section  28  may be welded or otherwise secured to the flow line  14 . In some alternative embodiments, the bulk material sensor  20  need not be directly connected to the flow line  14 , but may be arranged fixedly adjacent to the flow line  14 , such as in a case where the signal emitted from the bulk material sensor  20  and reflected energy signals from passing particles of bulk material  12  are passable through a wall of the flow line  14  without substantial loss of accuracy in the sensed signal, depicted schematically as  30 , emitted from the bulk material sensor  20 . 
     One embodiment of a gas speed sensor  22  for measuring the gas flow speed in the flow line  14  is schematically depicted in  FIG. 1 . While alternatively termed “airflow” sensor, it should be understood that the gas speed sensor  22  may be capable of detecting speeds of any conveyed gas. Although, in one embodiment, air is employed to pneumatically convey the bulk material  12  through the flow line  14 , the system  10  may allow the use of alternative gases there through. The speed of gas flow may be measured in feet/sec, meter/sec, or any other units used to measure speed, to output a gas speed signal, depicted schematically at  32 . Various types of gas speed sensors  22  may be used, including various types of anemometers and sensors that use both velocity sensing elements as well as temperature sensing elements to improve the accuracy of the velocity measurements. The gas speed sensor  22  may include at least a portion  23  positioned within the flow line  14 . One possible, non-limiting example of a gas speed sensor incorporable within the system  10  is the QuadraTherm flow meter commercially available from Sierra Instruments, Inc., although other commercially available gas speed sensors that are capable of measuring the gas flow speed within the flow line  14  may also be incorporated into the system  10  as the gas speed sensor  22 . 
     With the use of both the bulk material sensor  20  and the gas speed sensor  22 , the system  10  is not limited to gravity driven bulk material passage, and does not require airspeed assumptions in order to calculate the flow rate of the passing bulk material  12 . That is, the two signals  30 ,  32  from the bulk material sensor  20  and the gas speed sensor(s)  22  can be sent to a control system  34  to be combined by the controller  34  to calculate a variable accurate determination of bulk material flow rate. The system  10  thus provides the ability to accurately calculate bulk material flow rate at any air speed or product quantity. 
     One application of the system  10  is shown in  FIGS. 2 and 3 , where assembly  50  is but one example of how the system  10  may be employed. The assembly  50  includes a dry bulk material vessel, such as tank  52 . The tank  52  may be pressurizable. The tank  52  includes at least one entry port  54  for delivering the bulk material  12  into the tank  52 , and at least one exit port  56  for allowing the bulk material  12  to exit the tank  52 . In the illustrated embodiment, the tank  52  includes three exit ports  56 , although any number of exit ports  56  may be provided. As illustrated, the tank  52  is towable on a wheeled trailer bed  58 , pullable by a truck (not shown). Alternatively, the tank  52  may be provided on a train platform or other transportable platform such as a floating rig. In yet another alternative embodiment, the tank  52  may simply be provided on a non-movable surface such as the ground or a factory floor. 
     The exit port(s)  56  of the tank  52  fluidically communicate with the flow line  14 . As the flow line  14  is situated at the belly of the tank  52 , the flow line  14  may alternatively be termed a “belly line” in the assembly  50 . Each exit port  56  may be provided with a separate flow control valve  60  to permit or block the exit of bulk material  12  from the respective exit port  56  into the flow line  14 . One or more hoppers  62  may be provided in the tank  52  to direct the bulk material  12  towards respective exit ports  56 . 
     The blower  16  is provided on the trailer bed  58  and provides a source of pneumatic pressure to the assembly  50 . The pneumatic pressure may be delivered into the assembly  50  or blocked therefrom by valve  64  ( FIG. 2 ). The blower  16  may provide pneumatic pressure to the tank  52  through line  66 . A pressure transducer  68  may be employed on the line  66  to sense the pressure within the assembly  50  that is moving into the tank  52 . A flow control valve  70  may permit or block fluidic communication between the blower  16  and the tank  52 . The tank  52  is pressurizable by the blower  16  to create exiting flow and a force to the exiting dry bulk material  12  into the flow line  14 . The air coming into the tank  52  by the blower  16  may additionally pressurize the tank  52  to a certain degree, such that the airflow speed exiting the tank  52  may actually be greater than airflow speed entering the tank  52  at a specific moment, such as when the airflow has been coming into the tank  52  for a period of time and pressurizing the tank  52  prior to opening the valves  56  at the exit ports  56 , and then the valves  56  are opened. 
     The assembly  50  may further include an aeration line  72  fluidically connected to the blower  16 . A valve  74  on the aeration line  72  may permit or block fluid pressure from the blower  16  into the aeration line  72 . The aeration line  72  is fluidically connected to an interior  76  of the tank  52  adjacent each exit port  56  such that the air from the aeration line  72  may be used to fluff up the dry bulk material  12  within the tank  52 . The aeration line  72  may connect to the hoppers  62  and create a little whirlwind to fluidize the exiting material  12 . Upstream of the aeration line  72 , the flow line  14  may be connected to the blower  16  by a check valve  78  to allow pressure from the blower  16  to be delivered to an upstream end  80  of the flow line  14 . Such pneumatic pressure may be permitted or blocked by valve  82 , and sensed by pressure transducer  84 . Thus, the lines  66 ,  86 ,  88 ,  90 , and  92  that are in fluidic communication with the blower  16  are split and controlled by the various flow control valves  64 ,  70 ,  74 , and  82  for selectively directing pneumatic pressure from the blower  16  into the tank  52 , flow line  14 , and aeration line  72 . 
     The flow line  14  provides a flow path for the dry bulk material  12  to escape the assembly  50 . That is, the material  12  is moved in direction  18  to an exit  94  and discharge portion  95  of the assembly  50 . In the illustrated assembly  50 , two sensors  20 ,  22  are employed adjacent an end of the trailer bed  58  and close to the exit  94  of the assembly  50 . The sensors  20 ,  22  may be welded or otherwise secured to, or relative to, the product line  14 . In the illustrated embodiment, both sensors  20 ,  22  are located on the downstream “dirty” side of the assembly  50 . Additional sensor(s)  22  are depicted on the upstream “clean” side of the assembly  50 . The gas speed sensor(s)  22  may be included at one or more of the depicted locations, and for different assemblies the locations for the gas speed sensor(s)  22  may be adjusted accordingly. Signals  30 ,  32  from the sensors  20 ,  22  are provided to the controller  34  ( FIG. 1 ) which may be provided in control housing  96  ( FIG. 3 ). 
     With reference now to  FIG. 4 , the assembly  50  containing the system  10  is depicted at a location within an operation system  150 . In the illustrated embodiment, the location is a wellsite  120  and the operation system  150  is for a hydraulic fracturing operation. While the system  10  may be used in a number of different manufacturing and industry environments, the system  10  is particularly useful in a hydraulic fracturing operation for pumping a fluid, such as a hydraulic fracturing fluid, from a surface  112  to a borehole  115 . The borehole  115  may be cased or uncased, or include any other tubular  117  provided with perforations or openings for fracturing fluid to pass towards the formation wall  119 . The operation system  150  (a fluid processing system) includes a blender  122 . The blender  122  includes, in part, a blender tank or tub  124  for blending components of the fracturing fluid. Components of the fracturing fluid may include a base fluid (such as water), material  112  (such as proppant/sand), and various other additives to form a slurry of the hydraulic fracturing fluid. The base fluid may be stored in one or more water tanks  126  in a fluid supply  128 . In one embodiment, prior to blending, the base fluid may be passed through a hydration system  130 , which combines the base fluid with additives for a sufficient amount of residence time within a hydration tank  132  of the hydration system  130  to form a gel. The gel from the hydration tank  132  may then be directed to the blender  122  for combining with bulk material  12 , such as proppants, stored in sand trucks, silos or other sources, such as tank  52  ( FIGS. 2 and 3 ), which may be positioned to pass the bulk material  12  through the system  10  prior to delivering the material  12  to the blender  122 . The material  12  may, in one embodiment, be delivered to the blender tub  124  using a conveyor system  134 . Knowing the flow rate of the material  12  being delivered into the blender tub  124  is useful information for correctly adjusting the quantities of the components of the fracturing fluid. The fracturing fluid is pumped from the blender  122  to a fracturing pump assembly  138  along line  140 . The fracturing pump assembly  138  may include one or more fracturing pumps  142  (also known as “frac” pumps). While only one fracturing pump assembly  138  is depicted, a manifold may provide the fracturing fluid to multiple fracturing pump assemblies  138 . The hydraulic fracturing fluid is then deliverable into the borehole  115  at high pressures by the one or more fracturing pump assemblies  138 . 
     Any or all of the components of the system  150 , including the blender  122 , hydration system  130 , conveyor system  134 , fluid supply  128 , pneumatic bulk material assembly  50 , and fracturing pump assembly  138  may be provided on trailer beds, trucks, or other movable/wheeled platform or transportable surfaces  146  to assist in delivery of the components to the well site  120 , and to enable such components to be reconfigured as needed at the wellsite  120 , and quickly removed from the well site  120  when the process is completed. Alternatively, in an embodiment where the system  150  is utilized for an offshore well, the components may be positioned on a suitable fracturing and stimulation vessel (not shown). 
     While particular arrangements of a system  10 , assembly  50  and operation  150  have been shown in  FIGS. 1-4 , it should be understood that the system  10  may have alternate arrangements and may be incorporated into alternate assemblies, operations, and methods where bulk material  12  is blown into a line and carried pneumatically. 
     Thus, the system  10  described herein looks at bulk material  12  in a flow line  14  being conveyed pneumatically and uses a combination of signals  32 ,  30  from a sensor  22  to measure air speed and a sensor  20  to measure particles in the air within the flow line  14  to calculate a bulk material flow rate of the bulk material  12 . The system  10  can be fully contained in a pneumatically pressurized environment by the arrangement of the sensors  20 ,  22  relative to the flow line  14 . The sensor  22  detects and measures the gas flow and outputs a gas flow rate. The sensor  20  detects the amount of bulk materials  12  in the detection range  26  and outputs a quantity or a percent of material  12  in the range  26 . These two signals  30 ,  32  are combined together to calculate a variable accurate determination of bulk material flow rate. The system  10  advantageously is able to accurately determine bulk material flow rate at any air speed. Calculating measurements from the two sensors  20 ,  22  together may change slightly depending on different sensors  20 ,  22  used. Also, for different assemblies, proper placement of sensors  20 ,  22  for accurate readings may be altered. Further, different types of sensors  20 ,  22  will affect the accuracy of the results, and the determination of which type of sensors  20 ,  22  is employed in a particular assembly may depend on environment, cost, ease of use, etc. 
     Set forth below are some embodiments of the foregoing disclosure: 
     Embodiment 1: A dry bulk pneumatic metering system comprising: a flow line configured for the passage of pneumatically-conveyed bulk material; a bulk material sensor arranged relative to the flow line, the bulk material sensor configured to send a first signal related to a quantity of the bulk material passing in the flow line and within a range of the bulk material sensor; a speed sensor arranged with respect to at least one area of the system, the speed sensor configured to send a second signal related to the speed of gas flow at the at least one area of the system; and, a controller arranged to receive the first and second signals and configured to calculate a bulk material flow rate of the bulk material using the first and second signals. 
     Embodiment 2: The dry bulk pneumatic metering system of any of the proceeding embodiments, wherein the speed sensor includes at least one portion arranged within the flow line. 
     Embodiment 3: The dry bulk pneumatic metering system of any of the proceeding embodiments, wherein the bulk material sensor utilizes one of an optical signal and a radar signal. 
     Embodiment 4: The dry bulk pneumatic metering system of any of the proceeding embodiments, further comprising a plurality of speed sensors. 
     Embodiment 5: The dry bulk pneumatic metering system of any of the proceeding embodiments, wherein the at least one area of the system does not pass the bulk material therethrough. 
     Embodiment 6: The dry bulk pneumatic metering system of any of the proceeding embodiments, further comprising a pressurizable tank configured to hold a source of the bulk material, the tank including at least one exit port fluidically connected to the flow line. 
     Embodiment 7: The dry bulk pneumatic metering system of any of the proceeding embodiments, further comprising a blower arranged to pressurize the pressurizable tank. 
     Embodiment 8: The dry bulk pneumatic metering system of any of the proceeding embodiments, further comprising a blower line connecting the blower and the flow line, the blower line bypassing the tank. 
     Embodiment 9: The dry bulk pneumatic metering system of any of the proceeding embodiments, further comprising an aeration line fluidically connected to the blower line, the aeration line arranged to blow gas into the tank adjacent the at least one exit port. 
     Embodiment 10: An operating system comprising: a material receiving member; and, the dry bulk pneumatic metering system of claim  1 , the dry bulk pneumatic metering system further including a discharge portion arranged to discharge the bulk material from the dry bulk pneumatic metering system; wherein the bulk material discharged from the dry bulk pneumatic metering system is delivered to the material receiving member. 
     Embodiment 11: The operating system of any of the proceeding embodiments, wherein the material receiving member is one of a blender tub, a mixing tub, and a tank. 
     Embodiment 12: The operating system of any of the proceeding embodiments, wherein the bulk material is used in the material receiving member to blend a hydraulic fracturing fluid. 
     Embodiment 13: The operating system of any of the proceeding embodiments, wherein the material receiving member is a blender, and further comprising a high pressure fracturing pump configured to receive the hydraulic fracturing fluid from the blender. 
     Embodiment 14: A method of determining a bulk material flow rate in a dry bulk pneumatic metering system, the method comprising: pneumatically conveying bulk material through a flow line of the system; sensing a quantity of the bulk material passing within the flow line and within a range of a bulk material sensor, the bulk material sensor arranged relative to the flow line, the bulk material sensor sending a first signal to a controller of the system; sensing a speed of gas flow at at least one area of the system using a speed sensor, the speed sensor sending a second signal to the controller; and, using the first and second signals in the controller to calculate the bulk material flow rate of the bulk material. 
     Embodiment 15: The method of any of the proceeding embodiments, wherein pneumatically conveying bulk material through the flow line includes pneumatically conveying the bulk material at variable rates. 
     Embodiment 16: The method of any of the proceeding embodiments, wherein pneumatically conveying bulk material through the flow line includes using a blower for conveyance. 
     Embodiment 17: The method of any of the proceeding embodiments, further comprising supplying the flow line with the bulk material from a tank containing a source of the bulk material, the tank having an exit port in fluid communication with the flow line, and pressurizing the tank with the blower. 
     Embodiment 18: The method of any of the proceeding embodiments, wherein sensing the quantity of the bulk material includes using one of a radar and an optical signal. 
     Embodiment 19: The method of any of the proceeding embodiments, wherein sensing the speed of gas flow at at least one area of the system using the speed sensor includes sensing the speed of gas flow at an area of the system through which the bulk material does not pass. 
     Embodiment 20. The method of any of the proceeding embodiments, wherein sensing the speed of gas flow at at least one area of the system using the speed sensor includes sensing the speed of gas flow in the flow line. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Further, it should further be noted that the terms “first,” “second,” and the like herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the particular quantity). 
     The teachings of the present disclosure may be used in a variety of well operations. These operations may involve using one or more treatment agents to treat a formation, the fluids resident in a formation, a wellbore, and/or equipment in the wellbore, such as production tubing. The treatment agents may be in the form of liquids, gases, solids, semi-solids, and mixtures thereof. Illustrative treatment agents include, but are not limited to, fracturing fluids, acids, steam, water, brine, anti-corrosion agents, cement, permeability modifiers, drilling muds, emulsifiers, demulsifiers, tracers, flow improvers etc. Illustrative well operations include, but are not limited to, hydraulic fracturing, stimulation, tracer injection, cleaning, acidizing, steam injection, water flooding, cementing, etc. 
     While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims. Also, in the drawings and the description, there have been disclosed exemplary embodiments of the invention and, although specific terms may have been employed, they are unless otherwise stated used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention therefore not being so limited.