Abstract:
Disclosed herein is a system for degassing a fluid including a sample probe in operable communication with a pump which is in operable communication with a gas trap wherein one or more nozzles are located to accelerate and expel the fluid into the gas trap thereby liberating dissolved gases in the fluid. A method for degassing a fluid is also disclosed. The method includes directing a pressurized fluid toward one or more nozzles and accelerating and expelling fluid through the nozzles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of an earlier filing date from U.S. Ser. No. 60/514,869 filed Nov. 27, 2003, the entire contents of which is incorporated herein by reference. 
     
    
     BACKGROUND  
       [0002]     In the hydrocarbon industry, wellbores are drilled based upon available geological data. Many times the expectation of accessing a hydrocarbon bearing formation are realized. Unfortunately, however this is not always the case. For this reason, among others, methods and apparatus are employed to gain information as the process continues.  
         [0003]     One of those methods and apparatus relates to determining a quantity of a gas dissolved in the drilling mud. This provides valuable information about the probability that a particular formation being accessed will bear profitable hydrocarbon levels because formation solids, where that formation is a hydrocarbon bearing one, tend to have gas dissolved therein of a type(s) associated with the existence of profitable hydrocarbons nearby. The more gas present, the more likely the formation will prove profitable.  
         [0004]     Drilling mud has been tested for the presence of dissolved gases in the prior art but the devices used for the extraction and liberation of gas from the drilling fluid are complex, require a large amount of space and therefore must be placed some distance from the wellhead. Distance is deleterious to the process as gases come out of solution and dissipate en route to the device. This often leaves too little gas to be measurable or if still measurable causes uncertainty regarding actual amount of gas being accessed due to uncertainty regarding the precise amount of off-gassing while en route and the amount of dissipation of that released gas.  
       SUMMARY  
       [0005]     Disclosed herein is a system for degassing a fluid including a sample probe in operable communication with a pump which is in operable communication with a gas trap wherein one or more nozzles are located to accelerate and expel the fluid into the gas trap thereby liberating dissolved gases in the fluid.  
         [0006]     A method for degassing a fluid is also disclosed. The method includes directing a pressurized fluid toward one or more nozzles accelerating and expelling fluid through the nozzles. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     Referring now to the drawings wherein like elements are numbered alike in the several Figures:  
         [0008]      FIG. 1  is a view of gas trap system disclosed herein;  
         [0009]      FIG. 2  is a perspective view of a sample probe;  
         [0010]      FIG. 3  is a schematic top plan view of the sample probe of  FIGS. 1 and 2 ;  
         [0011]      FIG. 4  is a bottom plan view of a strainer of the sample probe;  
         [0012]      FIG. 5  is a bottom plan view of the blade of the sample probe;  
         [0013]      FIG. 6  is a schematic bottom plan view of the sample probe; and  
         [0014]      FIG. 7  is a perspective schematic view of the gas trap of the  FIG. 1  system. 
     
    
     DETAILED DESCRIPTION  
       [0015]     Referring to  FIG. 1  an embodiment of a gas trap system in accordance with this disclosure is illustrated. For clarity, each of the major operational elements of the device are introduced first with discussion of the specifics of each element following.  
         [0016]     System  10  comprises a sample probe  50  in operational communication with a pump  100 . The pump  100  provides a motive force for a fluid such as drilling mud to be extracted by the sample probe  50  and to, under pressure, deliver the fluid to a gas trap  150  wherein the pressurized fluid is expelled through at least one nozzle (discussed below) to cause degassing of the fluid. The gas is then caused to enter a measuring apparatus  200 . The degassed fluid is returned to a fluid holding tank or a flow of the fluid. The measuring apparatus  200  may be integral with the gas trap  150  or may be a remote unit connected to the gas trip via appropriate conduit. The system is small in size and lends itself to installation wherever desired. Often the most desirable flow is nearest the original exit of mud from the wellbore. The system described herein can be installed right at the wellhead.  
         [0017]     Addressing the elements of the system individually, reference is made to  FIGS. 1-6  wherein several views related to the sample probe  50  are provided. Many of the components of this element are numbered in each of the views. Review of all of the views together may assist in developing an understanding of the element.  
         [0018]     Sample probe  50  has a fluid pick-up function. Since the fluid that is picked up is in this embodiment (e.g. drilling mud returning from a downhole environment where formation materials are being comminuted to create a borehole) the mud is commonly a carrier for particulate matter that is not desired to be introduced to the gas trap system  10 . For this reason probe  50  includes a strainer  52 . The strainer  52  ( FIG. 4 ), in one embodiment, is a plate having a plurality of through holes  54  and which holes may be angularly counter sunk  56 . Strainer  52  also includes a through bore  58  for a shaft. In one embodiment, the collective surface area occupied by holes  54  is 50 square millimeters. It will be appreciated that the primary purpose of the strainer  52  is to prevent ingress of particles to sample probe  50 , and therefore the rest of the system. The particular configuration and makeup of the strainer  52  could be altered without difficulty. Strainer  52  is connected to tube  60  through which fluid is taken up.  
         [0019]     In order to keep strainer  52  clear of debris that might otherwise inhibit desired fluid flow therethrough, blade  62  ( FIG. 5 ) is in operable communication with the sample probe  50 . In the illustrated embodiment, blade  62  has four lobes  64 . Fewer or more lobes could be substituted although it will be understood that more lobes may have an adverse effect on total available fluid passage area depending upon both number and width of individual lobes. This may or may not be a problem depending on design parameters of the system and flow rate desired. Blade  62  is configured to be driven by a shaft  66  in any of a number of known ways, such as by a pneumatic drive, electric motor, hydraulic motor, internal combustion motor, etc.  
         [0020]     Shaft  66  extends to body  68  of sample probe  50 . Within body  68  is a drive  70  configured to move blade  62  to clean strainer  52  of debris. Drive  70  in one embodiment is a pneumatic drive and is run by a compressed air source such as rig air. Referring to  FIG. 3 , an upper end of shaft  66  is visible connected to arm  72 . Arm  72  is pivotally connected to drive rod  74 , which rod may be a piston rod. Rod  74  is driven by drive  70 , which in one embodiment comprises a pneumatic cylinder. In the illustrated embodiment, drive  70  is pivotally mounted to body  68  via pivot mount  76 . In one embodiment hereof, drive  70  is configured to cause rotation of blade  62  through 90 degrees of motion or less if blade  62  encounters resistance. In the event resistance is encountered, blade  62  is caused by drive  70  to reverse direction. An alarm at a control location is also contemplated in the event of a direction reversal. The alarm may be visual or audible or both as desired and appropriate.  
         [0021]     Referring back to  FIG. 1 , tube  60  further includes a fluid output connection  78  which may be any suitable connection to a conveying conduit such as hose  80  to pump  100 .  
         [0022]     Pump  100  may be of any type capable of moving mud into probe  50  through the pump and into gas trap  150  in a pressurized condition. In one embodiment hereof a peristaltic pump, commercially available from many locations, is employed due to its simplicity, reliability, low cost, and ease of operation and maintenance. The pump  100  comprises an inlet  102  and outlet  104 . Driving fluid through both inlet and outlet is a pair of rollers  106  on a centrally located and rotationally driven roller arm  108 . The rollers  106 , as illustrated in  FIG. 1 , compress hose  110  as they roll thereover. The compressed hose effectively seals the same and the rolling motion urges material therein in the direction in which the roller  106  is traveling. Fluid exiting pump  100  through outlet  104  is conveyed to a gas trap  150  through suitable means such as a conduit  112 . The discharge rate of the pump  100  is not critical to operation but it is desirable for that rate to remain constant.  
         [0023]     Still referring to  FIG. 1 , one embodiment of a routing of conduit  112  to gas trap  150  is illustrated. In this embodiment, conduit  112  is split at a junction  114  into conduits  116  and  118 , which connect to a gas trap housing  152  at nozzles  154  and  156 , respectively. The nozzles are configured to accelerate fluid passing therethrough and are directed generally toward each other to cause pressurized fluid exiting from nozzles  154  and  156  to collide within housing  152  thereby liberating dissolved gas there. Nozzles of 4.8 mm are employed in one embodiment. In one embodiment, nozzles  154  and  156  point directly at one another for a “head-on” impact of the pressurized fluid. The fluid could, of course, intersect at an angle. In other embodiments of gas trap  150  a single nozzle may be employed with pressurized fluid impacting an opposing wall of housing  152  or a structure (or target) within housing  152 . In such case only one of conduits  116  and  118  and one of nozzles  154  and  156  would be needed.  
         [0024]     The gas trap  150  referring to  FIGS. 1 and 7 , further comprises a cover  158  with a fluid inlet  160  and a fluid outlet  162  and a securement arrangement illustrated as a t-bolt  164  and wing nut  166 . Securement may of course be effected by other equivalent means. In this embodiment, inlet  160  allows atmospheric fluid to flow into housing  152  to mix with evolved gases prior to that mixture being drawn off through outlet  162  to gas measuring device  200 .  
         [0025]     Further illustrated, in  FIGS. 1 and 7 , is an auxiliary level tank  170 . An exit from the tank will return mud to the flow. Alternatively, the tank  170  can be omitted, with the gas trap directly connected to a flow for redeposit of the degassed mud. It will be appreciated from  FIG. 1  that the mud fluid level in tank  170  is maintained above the bottom edge  172  of housing  152  to avoid the unintentional addition of excess gas from other sources to the housing  152  interior. The tank  170  in this embodiment includes a spillway  174  leading back to a mud circulation system. It will be appreciated that the spillway is located above the lower edge  172  of housing  152  to help ensure that the mud level does not fall below lower edge  172  of housing  152 .  
         [0026]     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.