Abstract:
The gas trap collects formation gases from oil well fluid flow in real time. Gases are released by the fluid when agitated by an agitating pipe which stirs the fluid flow; the gases are then collected and separated from the fluid to be analyzed. The gas trap does hinder the flow of formation cuttings in the drilling fluid flow line, but allows the formation cuttings to flow around the agitator pipe and out to the sample box.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     Provisional Patent 61/457,280, filed Feb. 17, 2011. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     None. 
     THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT 
     None. 
     INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC 
     None. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to the collection of formation gases to be analyzed as oil wells are drilled. 
     2. Background Art 
     The oil and gas industry has always treated the collection of formation gas and formation cuttings data as one function. On an oil and gas drilling project, there are two different applications. The first drilling application is the collection of formation gases and cuttings while the drilling fluid is directed to the reserve pits. The second drilling application is the collection of formation gases and cuttings while the drilling mud is directed to the steel pits. 
     The traditional configuration begins at the well head. From the well head, there is a flow line in which the drilling fluid leaves the well bore. The flow line is commonly six or eight inches in diameter. The flow line extends from the well head out towards the steel and reserve pits, where there are control valves that control the direction of the drilling fluid, either to the reserve pits, or to the steel pits. The reserve pits are located further away from the well bore and behind the steel pits. The drilling fluid from the well head carries the formation gases and formation cuttings from the well bore, to either the reserve pits, or the steel pits. The formation cuttings are dumped into the reserve pits, where they cannot reenter the drilling system. The formation gases are either released into the atmosphere, or flared off. The drilling fluid is then circulated around into the well bore, where the process is restarted. 
     Drilling Phase One—Water/Reserve Pits—At the beginning of a drilling project, the drilling fluid is either fresh water or brine water. The drilling fluid is bypassed the steel pits and out to the reserve pits, which are located behind the steel pits. The reserve pits are earth dug pits, in the shape of a horseshoe and at a slight angle. This allows the formation cuttings to be dropped out of the fluid. The fluid flows around to the other end of the horseshoe where it is suctioned back into the well bore. The flow line is an open ended system, so there is not any pressure on the flow line. The flow line is filled approximately halfway with drilling fluid. The drilling fluid is a mixture of formation gases and formation cuttings. The top half of the flow line is filled with formation gases. 
     Current practice in the industry is to insert a two-inch line into the flow of drilling mud, diverting it to the formation cuttings sample box that is installed near the end of the drilling fluid flow line and installed low enough, relative to the drilling mud source, so the fluid flows easily into the formation sample box. 
     The formation cutting sample box is a rectangular box, with a sliding door in the front. The formation cutting sample box is designed for catching formation cuttings, as well as holding enough drilling fluid for the agitator, for monitoring formation gas. Its width and length must be wide enough, to allow a sample box agitator stand to fit inside, and long enough, as not to hinder the collection of formation cuttings to be analyzed. It must also be built sturdy enough to withstand the vibration from the agitating motor, as well as the combined weight of the agitating stand and motor. The sliding door has a handle cut along its top edge. The handle is to allow excess fluid to flow out of the sample box, out into the reserve pits and not over the sides or end of the sample box. The sliding door is also used for washing formation cuttings out into the reserve pits, after a sample is collected, so that the next ten foot sample can be caught inside the sample box. 
     The sample box agitating stand is a steel stand about three to four feet tall, onto which the agitator motor is mounted. The stand has an entrance and exit portal in it that allows drilling fluid to enter and leave the box. An explosion-proof electrical agitator motor is mounted on the box which rotates beaters affixed to the motor&#39;s rotating shaft. A suction hole is drilled in the sample box to allow formation gases to be sucked out of the sample box to be analyzed. 
     Drilling Phase Two—Mudding Up/Steel Pits—At some point in the drilling process, the crews will begin to “mud up”, a term used by the oil and gas industry to describe the process of adding chemicals to the drilling fluid to control the properties of the drilling mud. At this point, the drilling fluid is now referred to as drilling mud. Once the determination has been made to start mudding up, the two valves are turned in the drilling fluid flow line and the flow is diverted from the reserve pits to the steel pits. Then chemicals are mixed to start the mudding up process. The drilling mud is directed to the steel pits to: 1) begin the mudding up process, 2) prevent loss of expensive drilling mud, 3) to maintain, control, and change the properties of the drilling mud, 4) to protect the well bore, and 5) to prevent or control lost circulation. 
     During the second phase, when drilling mud is used, the agitator stand is placed inside the sample box, at a lower bottom of a large vat, known as the possum belly, located in front of the shaker. The drilling fluid flow line enters into the possum belly at its base. The drilling mud fills the possum belly, until the drilling mud spills over the front edge, onto the shaker. The shaker includes screens and vibrates very rapidly. The drilling mud and formation cuttings spill onto the screens. The vibration of the shaker allows the drilling mud to fall through the screens, into the steel pits, leaving the formation cuttings on the screens. The drilling mud is remixed and suctioned back into the well bore. The formation cuttings are vibrated to the end of the shaker where they fall onto a slide. A sample of the formation cuttings is collected off the slide for examination. Formation gases are collected for monitoring at the possum belly. The remainder is washed off the slide, into the reserve pits. 
     The traditional method beats gases trapped out of the drilling fluid that is collected in the sample box, and only those gases. The sample box has to be moved when the drilling starts the mudding up process. The gas in the top half of the drilling fluid flow line simply escapes into the atmosphere and is never analyzed. Formation cuttings fill the formation cuttings sample box, plugging the hole at the base of the agitator bracket, and cause improper formation gas readings. The end result is that formation gases either cannot be monitored at all, or have very inaccurate readings. The traditional method also uses an agitating motor that vibrates, rusts, and requires electrical power in an outdoor installation. In such an environment, loss of power or a rusted motor renders the sampling system unusable. 
     The oil industry needs to be able to more efficiently sample the gases coming up out of the well with the drilling fluid. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention allows for the collection of formation gases by placement of an agitating pipe directly in the drilling fluid flow line; the pipe&#39;s opening cut at an angle so gas in the top half of the drilling fluid flow line (where there is no drilling fluid) will be collected and also analyzed, along with the gas agitated from the drilling fluid. Because of the design of the gas trap of the invention, formation cuttings will not plug up the gas trap, but flow around the agitator pipe and out to the sample box. As long as circulation is maintained, formation gas readings are maintained with the gas trap of the invention. No electricity or moving parts are used, eliminating issues associated with rusty motors and electrical power sourcing. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
       Exemplary embodiments of the gas trap are set forth in the figures below. 
       FIG.  1 —Exploded Orthogonal view of the Agitating Pipe with Ball Valve. 
       FIG.  2 —Plan view of the Spillway with Short Stack, Expansion Chamber, Collection Cap, and Long Stack. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Aspects of the present invention are disclosed in the following description and related figures directed to specific embodiments of the invention. Those skilled in the art will recognize that alternate embodiments may be devised without departing from the spirit or the scope of the claims. Further, the description and figures used herein should be viewed only as exemplary in nature. It can be appreciated that the exemplary embodiments described herein may include descriptions that related to specific sizes, shapes or types of material; however the methods, apparatuses and systems described herein are not limited to these particular sizes, shapes and types of materials. Instead, it may be appreciated that any desired materials may be utilized to form the methods, apparatuses and systems so as to achieve any desired results. Additionally, well-known elements of exemplary embodiments of the invention will not be described in detail or will be omitted so as not to obscure the relevant details of the invention. 
     As used herein the word “exemplary” means “serving as an example, instance or illustration.” The embodiments described herein are not limiting, but rather are exemplary only. It should be understood that the described embodiments are not necessarily to be construed as preferred or advantageous over other embodiments. For example, the description below discusses PVC, the common abbreviation for polyvinyl chloride, a popular thermoplastic polymer, that is used to construct the invention, but many other materials can be used. 
     As shown in  FIGS. 1 and 2 , the Gas Trap is typically constructed using  2 ″ PVC or other suitable materials, comprising an Agitating Pipe  19  and Collection Cap,  21 . Optional components include a Ball Valve  31 , Short Stack  41 , Long Stack  51 , Spillway  61 , and Extension Gas Chamber  71 , as needed. Each is explained below. 
     As shown in  FIG. 1 , the Agitating Pipe Subassembly comprises two male Couplings  13 ,  15 , with a Nipple  17  between them, and an Agitating Pipe  19  attached to the lower Coupling  13 . In  FIG. 1 , an optional Ball Valve  31  is used. As shown in the figures, the Agitating Pipe  19  is a piece of pipe cut to a length that is close to the inside diameter of the drilling fluid flow line, and cut to an angle that makes the agitating pipe&#39;s Collection Opening  23  inside the flow line pipe as large as possible, extending into the fluid flowing through the flow line pipe, but not colliding with the opposite inside side of the flow line pipe as the Agitating Pipe  19  is installed. The angle is determined by the length of the pipe. The Agitating Pipe  19  is cut and attached to a Coupling  13 , which mounts onto the wall of the fluid flow line. The Agitating Pipe  19  is installed with the angled Collection Opening  23  so it faces the flow of the drilling fluid or mud, so when the fluid reaches the Agitating Pipe  19 , the fluid is agitated and gas is released from the flow material. This gas adds to the presence of gases already present in the flow line, all of which flows into the Collection Opening  23 , travels through the Agitating Pipe  19 , into the Collection Cap  23  ( FIG. 2 ) and then goes through the Sample Tube  27  ( FIG. 2 ) to the test equipment that analyzes the gas. 
     As shown in  FIG. 2 , the Collection Cap  21  is a two-inch PVC threaded cap with a barbed hose Adaptor  25  screwed into its center. A flexible Sample Tube  27  slips over the Adaptor  25 . Formation gases leave the Gas Trap through the Sample Tube  27  and into the testing apparatus (not part of the invention). 
     As shown in  FIG. 1 , an optional Ball Valve  31  may be installed on the Agitating Pipe  19  for the convenience to the operators, and not necessary to the invention, but very helpful to operators. 
     As shown in  FIG. 2 , an optional Short Stack  41 , comprising a length of PVC pipe with a male coupling affixed to one end and a female coupling on the other, may be installed between the Agitating Pipe  19  and Collection Cap  21  to prevent drilling fluid that might otherwise be drawn into the Collection Cap  21 , or used between the Agitating Pipe  19  and Spillway  61  assembly. The actual length of the pipe can vary to whatever length is necessary to prevent the fluid from reaching the Collection Cap  21 . 
     As shown in  FIG. 2 , the Spillway  61  is a PVC pipe subassembly installed on the top opening of the Agitating Pipe  19 . Its purpose is to further allow gases within the drilling fluid to separate from the fluid inside the Agitating Pipe, prevent the Collection Cap  21  from being clogged with drilling fluid, and to allow an escape of the fluid from the Agitating Pipe  19 . It can be constructed in many different ways, but is currently configured with a PVC Female Tee  63 , with a Collection Cap  21  mounted on the side opening, and the main line connection of the Tee  63  attached to the Agitating Pipe  19  through a 45° Coupling  69  on one side, and a drilling fluid discharge route wherein the fluid flows through the Female Tee  63 , an Elbow  65 , and 45° Discharge Coupling  67  and optional Long Stack  51  drilling mud exit pipe mounted on the other side. 
     Shown in  FIG. 2 , the Extension Gas Chamber  71  is an optional component length of pipe added between the Tee  63  of the Spillway Assembly  61  and the Collection Cup  21  to reduce the danger that drilling mud may be drawn into the Collection Cup  21 . 
     Shown in  FIG. 2 , an optional Long Stack  51  is an added length of pipe used as an extension on the end of the Spillway, affixed to the open end of the 45° male coupling to prevent splashing of the drilling mud when the drilling mud is directed into the possum belly. It is also used in the sample box to prevent splashing of the drilling mud, when catching formation samples while the possum belly is being bypassed. 
     The invention can be made with many different configurations. The specific discussion and explanation above is not intended to be a limiting description of the invention, but merely one embodiment as the invention is currently constructed.