Abstract:
An improved gas analyzer for analyzing the concentrations and amounts of one or more different gases in drilling mud returning from a borehole is disclosed. An oil well drilling rig re-circulates the drilling mud by continuously pumping it through a gas separation means. The gas separation means generally includes a fluid stop, a bubble jar and a dririte chamber in order to separate the gases from the drilling mud. A gas sample from these separated gases can be mixed with a carrier gas and are conveyed to gas analyzing means where the concentration of the different hydrocarbon components of the gases in the mud can be continuously measured.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a continuation of U.S. patent application Ser. No. 12/514,951 entitled “Gas Analyzer,” which was filed on May 14, 2009, and which is the U.S. national phase application of International Application No. PCT/US08/79722, filed on Oct. 13, 2008 under the PCT (Patent Cooperation Treaty), which designated the US and claims priority to U.S. Provisional Patent Application No. 60/981,873, filed Oct. 23, 2007. The entire contents of these applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    Embodiments are generally related to drilling and/or environmental operations. Embodiments are additionally related to well logging techniques utilized during drilling operations. Embodiments are also related to methods and systems for analyzing the concentration and amount of gas produced from mud during drilling of an oil well. 
       BACKGROUND OF THE INVENTION 
       [0003]    In oil well drilling operations, a drill bit can be mounted on the end of an elongated rotating drill string which turns the bit and causes it to cut away the underlying earth and rock formations. During this operation, a drilling mud is continuously pumped down through the drill string and into the region around the drill bit and then back up to the surface. This drilling mud is typically made up of clays, chemical additives and/or an oil or water base and performs two important functions. First, the drilling mud acts as a coolant and lubricates the drill bit during operation and it collects the drill cuttings and carries them back to the surface of the well. Second, the drilling mud also serves to maintain a hydrostatic pressure, which prevents pressurized gases from the earth from blowing out through the drilled well. In addition, the mud may pick up and entrain gases present in the bottom of the well and deliver them to the surface along with the drill cuttings. 
         [0004]    Drilling mud generally constitutes a liquid carrier, typically water or diesel oil, which is mixed with additives. In the case of a water-based mud, this may include bentonite day and various chemicals. The mud carries out several functions for assisting in the drilling process, including carrying away cuttings and fine solids produced by the drill bit as it bores through the rock. Entrained solids raise the mud&#39;s density and viscosity, leading to many drilling problems, including a reduced rate of penetration, loss of mud downhole and filter cake buildup. The portion of the drilling mud being returned from the well which includes various gaseous components to be analyzed must be separated from the mud. 
         [0005]    It has been common in the past to provide a log of the drilling operation that will permit the nature of the earth formation through which the drill bit is penetrating. The log enables the drilling operator to ascertain the presence of oil or gas in the formation being drilled and also the location of such oil or gas in the well. As part of this logging operation, samples of the drill cuttings from predetermined depths of the well are collected and analyzed. Generally, these samples can be collected to represent a desired interval of drilling, such as every ten feet of well drilled or every thirty feet drilled. 
         [0006]    In a majority of prior art mud logging systems, the information recorded from the drilling mud reaching the surface of the well, is generally done on a manual basis. All of the measurements and the measuring equipment require constant supervision so a logging operation generally involves two mud loggers each working alternate twelve-hour shifts. The well mud logging techniques have also made use of gas chromatography to ascertain the presence of different hydrocarbon species in the mud being returned. The gas chromatography technique involves taking samples of gas from the drilling mud and passing that gas through special columns filled with materials that allow different gases to flow at different rates. A further disadvantage of the prior art chromatographic gas analysis technique results from the fact that it is not possible to separate all of the hydrocarbon gas from the returning mud and therefore it is not possible with chromatographic analysis to ascertain the actual concentration of any species in the mud. 
         [0007]    Based on the foregoing it is believed that a need exists for an improved system and method for analyzing the concentrations and amounts of one or more different gases from the mud produced by drilling an oil well. 
       BRIEF SUMMARY 
       [0008]    The following summary is provided to facilitate an understanding of some of the innovative features unique to the embodiments disclosed and is not intended to be a full description. A full appreciation of the various aspects of the embodiments can be gained by taking the entire specification, claims, drawings, and abstract as a whole. 
         [0009]    It is, therefore, one aspect of the present invention to provide for improved well logging during drilling. 
         [0010]    It is another aspect of the present invention to provide for improved system and method for analyzing the concentrations and amounts of one or more different gases in drilling mud returning from the borehole. 
         [0011]    The aforementioned aspects and other objectives and advantages can now be achieved as described herein. An improved gas analyzer for analyzing the concentrations and amounts of one or more different gases in drilling mud returning from a borehole is disclosed. An oil well drilling rig re-circulates the drilling mud by continuously pumping it through a gas separation means. The gas separation means generally includes a fluid stop, a bubble jar and a dririte chamber in order to separate various gaseous components from the drilling mud. A gas sample from these separated gases can be mixed with a carrier gas and are conveyed to gas analyzing means where the concentration of the different hydrocarbon components of the gases in the mud are continuously measured. 
         [0012]    The carrier air can be passed through a silica gel scrubber and to a pump (e.g., Thomas pump), thereby maintaining the flow of the carrier air within predetermined parameters. The sample gas from the dririte chamber along with the carrier air is subjected to analysis in gas analyzing means to produce a component gas signal whose value corresponds to the concentration of the component in the gas mixture. The carrier air is simultaneously flowed at a rate such that the volume of carrier air is at least several times greater than the volume of the sample gas in the drilling mud. 
         [0013]    The sample gas is continuously subjected to different analysis in the gas analyzing means to produce different gaseous component concentration signals whose values at any instant represent, respectively, the concentrations at that instant of the different gaseous components in the separated gas. These different gaseous component concentration signals are processed continuously in signal processing means to provide a continuous logging signal and thus provides an indication of the instantaneous concentration of the different gaseous components in the drilling mud. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The accompanying figures, in which like reference numerals refer to identical or functionally-similar elements throughout the separate views and which are incorporated in and form a part of the specification, further illustrate the embodiments and, together with the de ailed description, serve to explain the embodiments disclosed herein. 
           [0015]      FIG. 1  illustrates a block diagram showing the major components of a mud analysis system, in accordance with a preferred embodiment; 
           [0016]      FIG. 2  illustrates a schematic representation of a gas separation means for separating gases from the drilling mud, in accordance with a preferred embodiment; and 
           [0017]      FIG. 3  illustrates a schematic representation of a gas analyzing means for analyzing the gaseous components in the gas separated from the drilling mud, in accordance with a preferred embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    The particular values and configurations discussed in these non-limiting examples can be varied and are cited merely to illustrate at least one embodiment and are not intended to limit the scope thereof. 
         [0019]    Referring to  FIG. 1  a block diagram showing the major components of a mud analysis system  100  is illustrated, in accordance with a preferred embodiment. The drilling mud analysis system  100  includes a gas separation means  120 , a gas analyzing means  170  and a monitoring unit  195 . The drilling mud  110  passes through the gas separation means  120  whereby the gas which includes various gaseous components to be analyzed can be separated from the drilling mud  110 . The sample gas  130  extracted from the drilling mud  110  can be directed to the gas analyzing means  170  where the sample gas  130  can be analyzed to ascertain their constituent parts and where other measurements are made. A carrier air  140  from a silica gel scrubber  150  can be passed through a pump  160  (e.g., a Thomas pump) to the gas analyzing means  170 . The Pump  160  can be adjusted in response to varying pressures and volumes of the carrier air  140  and thereby maintaining the flow of the carrier air  140  within predetermined parameters. The outlet of the pump  160  can be connected to the gas analyzing means  170  where various chemical and electrical tests are performed on the sample gas  130 . 
         [0020]    Atmospheric air is chosen as the carrier air  140  because of its ready availability and because it is relatively inert with respect to the hydrocarbons contained in the sample gas  130 . Other gases, such as nitrogen, may be used, for example where the ambient air contains an excess of impurities which could affect the sample gas measurements. The sample gas  130  is evenly mixed with the carrier air  140  and the amount of each individual gas can be determined by a Chromatograph (CG) analyzer  180  and the results can be monitored utilizing the monitoring unit  195 . For example, the quantity of methane, ethane, propane, isobutane, butane and pentane can each measured by the chromatograph analyzer  180 . Similarly, the total gas from the sample gas  130  can be analyzed by the Total Gas Analyzer (TGA)  175  to determine the total amount of gases produced. The exhaust  190  from the gas analyzing means  170  is then transferred to the Pump  160  which controls the flow of the gas  130  and  140  and disposing the gas via an exhaust out  185 . 
         [0021]    Referring to  FIG. 2 , a schematic representation of a gas separation means  120  for separating gases from the drilling mud  110  is illustrated, in accordance with a preferred embodiment. Note that in  FIGS. 1-3 , identical or similar parts or elements are generally indicated by identical reference numerals. The drilling mud  110  is generally captured from a drilling well (not shown). As stated before the process of capturing drilling mud  110  from the mud pit is well known in the art. The mud  110  passes through the gas separation means  120  where gases contained in the mud  110  can be extracted. The gas separation means  120  comprises an inlet line  42  connected to a fluid stop  36  wherein the mud sample gas  130  to be analyzed can be taken from the mud  110  just entering the gas separation means  120 . The fluid stop  36  can be utilized as a check flow stop, which removes any solid matter, so that drilling mud  110  does not enter the gas analyzing means  170 . 
         [0022]    Since the rate of mud flow through the well and the depth of the well are known, it is possible to relate the mud sample analysis to the location in the earth to which it pertains. The outlet  37  of the fluid stop  36  is connected to a bubble jar  40 . The bubble jar  40  can be filled with ethylene glycol in order to scrub it of water. A one-liter bubble jar  40  filled with  250  milliliters of ethylene can be installed between the fluid stop  36  and the outlet  41 . The outlet  41  of the bubble jar  40  can be attached to “Dririte” chamber  38  with an outside exhaust  44 . “Dririte” is ground anhydrite, which can be treated with an indicator that turns from blue to pink when saturated with water wherein some will be in its natural white state. 
         [0023]    The carrier air  140  from the silica gel scrubber  150  can be passed through an inlet  34  of a pump  160 . The outlet  24  of the Pump  160  is connected to the gas analyzing means  170  thereby maintaining the flow of the carrier air  140  within predetermined parameters. The flow of the sample gas  130  is indicated by line  20  and the flow of carrier air  140  is indicated by line  26 . The carrier air  140  is simultaneously flowed through the gas analyzing means  170  at a rate such that the volume of carrier air  140  is at least several times greater than the volume of mud sample gas  130  in the drilling mud  110 . The carrier air  140  can be taken from inside the unit in order to maintain a constant temperature. 
         [0024]    Referring to  FIG. 3  a schematic representation of a gas analyzing means  170  for analyzing the gaseous components in the gas separated from the drilling mud  110  is illustrated, in accordance with a preferred embodiment. Note that in  FIGS. 1-3 , identical or similar parts or elements are generally indicated by identical reference numerals. The carrier air  140  flows through a flow control valve  238  wherein a portion of the carrier aft  140  passes through a solenoid valve  206 , which controls the flow of the carrier air  140 . The line  240  is connected to activator  202  of the sample valve  224 . The activator  202  will move a diaphragm which will shift a plunger in the sample valve  224  which will change the connections of the ports. The majority of the carrier air  140  passes on through a pressure regulator  230 . Pressure gauge  232  can be utilized to display the pressure. 
         [0025]    The sample valve  224  includes seven ports identified as AIR IN PORT  234 , GAS IN PORT  228 , LOOP PORT A, LOOP PORT B, GAS IN PORT  218 , CG PORT  220  and AIR IN PORT  222 . The sample gas  130  can be captured at a rate anywhere from  3  standard cubic feet an hour (scfh) to 10 scfh. Normally it will be adjusted to capture about 6 scfh. Flow rotor  204  can be set to have an output of 6 scfh to flow control valve  216  which will exhaust 3 scfh. The output of the flow control valve  216  is connected to GAS IN PORT  228  and to valve  214 . Thus, sample gas  130  from the mud pit circulates through the loop  226  as well as directly into the total gas analyzer  175  as shown as filament  208  in  FIG. 3 . The port  222  and  218  is coupled and the output is passed through the filament  208  and to the exhaust  190 . The filament  208  actually comprises of two platinum filaments (not shown) with a common node, which acts as a total gas detector. One filament is sealed which acts as a reference filament. The other is open to the flow of sample gas  130  across it when fitted into the filament  208 . The filament  208  can be configured in a Wheatstone bridge configuration. 
         [0026]    Similarly, the output from CG port  220  is passed through a chromatograph  212 . The solenoid valve  206  can be controlled by a timer (not shown) so that every 5 minutes it activates to open the solenoid valve  206  so that line  240  is connected to activator  202  of the sample valve  224 . The activator  202  will move a diaphragm which will shift a plunger in the sample valve  224  which will change the connections of the ports. The preferred form of the sample valve  224  is a plunger running through a sleeve. O-rings on the plunger fit along the sleeve so that when the plunger is moved by the activator  202  that it will make the connections as described. It can be appreciated, however, that in accordance with other embodiments, other means can be utilized to make these connections. The plunger type operation is preferred because of its compact size, 
         [0027]    The gas within the loop  226  can be expelled through LOOP PORT A which is connected to the CG PORT  220 , when the valve  224  is switched from normal to closed position. The air  140  from AIR IN PORT  234  flows through LOOP PORT B. The air will push the accumulated gas in this path, the loop  226 , out through the CG PORT  220  which can take the gas through the chromatograph reader  212 , a separator  242  and filament  210 . The separator column  242  is made of copper ¼ in. O. D. copper tubing 70 inches in length. It is coiled to conserve space. The column  242  is packed with granulated diabutial phthilate, a product manufactured by Kodak Chemical of Rochester N.Y. It is provided as a liquid rubber. The packing is placed into the copper tubing forming the separation column  242 . 
         [0028]    The chromatograph  212  can show the amounts of each of the gases present. Methane comes out of the CG PORT  220  and can be measured as a pulse across the filament bridge  210 . It is followed by ethane, propane, isobutane, and normal butane in order of ascending molecular weight. As is well known, the chromatograph  212  will measure the first gas to be released from the column  242  which will be the methane. After the methane is measured, the second gas to be released from the separator may be ethane, after it is measured the next will be propane and so forth to pentane. The measurement of the amount of gases is the same in the total gas analyzer filament  208  and the chromatograph  212 . The gases are measured by the heat units they produce as they are flowed over a heated special material. 
         [0029]    Traditionally the material was platinum. In a preferred embodiment, the material for the filament can be a thermistor bead. The thermistor beads are a product of J. J. Enterprises in Baton Rough, La. It can be appreciated, however, that in accordance with other embodiments, other material can be utilized. Also in the event that there was some possibility there can be sufficient amounts of gases to cause the total gas analyzer  175  to go off the scale, (exceed its capacity) then it is possible to have an air dilution stream connected from an air flow to the flow control valve  238 . An equal amount of aft is pumped into flow control valve  238 . Therefore diluting the sample going to the total gas analyzer  175  to one half the otherwise calculated value. The exhaust  190  from the gas analyzing means  170  is then transferred to the pump  160  through the net  32  which controls the flow of the gas  130  and  140  and disposing the gas via an outlet  28  to the exhaust out  185 . 
         [0030]    Furthermore by providing appropriate additional valves, calibration gas sources and gas separation devices, it is possible to provide purging and calibration of the gas analyzing means  170  as well as backwashing of the gas separation means  120  so that different tests can be performed in rapid sequence. 
         [0031]    It will be appreciated that variations of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.