Patent Publication Number: US-2015059574-A1

Title: Vented Gas Drilling Fluid Catch Apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 13/623,219, filed Sep. 20, 2012, now U.S. Pat. No. 8,882,891, which claims the benefit of provisional patent application Ser. No. 61/537,944 filed on Sep. 22, 2011, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to oilfield equipment and specifically for a vented catch tank for drilling fluid overflow. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus for capturing drilling fluid. The apparatus comprises a drilling rig, a mud-gas separator located downstream from the drilling rig, a flare located downstream from the mud-gas separator, and a catch tank. The catch tank is located between the mud-gas separator and the flare. The catch tank comprises an inlet port having a closed end baffle and a mud opening such that mud entering the catch tank is directed downward by gravity and a gas line outlet in communication with the flare. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic representation of the apparatus of the current invention. 
         FIG. 2  is a side view of a catch tank for use with the apparatus of  FIG. 1 . 
         FIG. 3  is a cutaway perspective view of a catch tank for use with the apparatus of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The disclosed invention is directed to an apparatus  10  designed to catch drilling fluid, or mud, often a toxic and environmentally disfavored product, which is released in the gas line of a mud-gas separator due to high pressures and other upstream conditions in a drilling rig. A catch tank is provided as an additional measure to prevent drilling fluid, which is hot, corrosive, and toxic, from exiting the apparatus through a flare. Removing drilling fluid helps prevent corrosion and blockage in the gas ignition line, and prevents drilling fluid from escaping through the flare into the environment. One skilled in the art will appreciate that hot drilling fluid poses a hazard to equipment and operators. 
     With reference to  FIG. 1 , the apparatus  10  comprises a drilling rig  12 , a mud-gas separator  14 , a catch tank  16 , a gas ignition line  18 , and a flare  20 . Additionally, the apparatus  10  may comprise a panic line  22  to provide for catching drilling fluid in the case of extreme high pressure at the drilling rig  12 . The drilling  12  produces oil and/or gas for production purposes. Drilling rigs such as drilling rig  12  use drilling fluid to promote efficient subsurface drilling. This drilling fluid returns to the drilling rig  12  with gas from the subsurface. 
     Ordinarily, the mixture of gas and drilling fluid from the drilling rig  12  will be separated from produced gas in the mud-gas separator  14  before excess gas is ignited at the flare  20 . However, it should be understood that under high pressure, the capacity of an ordinary mud-gas separator  14  will be overcome and entrained drilling fluid will exit the mud-gas separator in the gas ignition line  18 . Therefore, the catch tank  16  is located downstream from the mud-gas separator  14  but upstream from the flare  20  as an additional measure to prevent drilling fluid from exiting via the flare. The catch tank  16  catches any excess mud and separates it from the gas. The gas is allowed to enter the gas ignition line  18  and is flared at the flare  20 . Drilling fluid is returned to a containment pit for processing and recycling through the apparatus  10 . 
     A panic line  22  is coupled to the drilling rig  12  to provide pressure release in case of a “blow out”. Under a “blow out” scenario, the flow rate of production at the drilling rig  12  will increase until the rig  12  cannot accommodate it, increasing pressure and putting the apparatus at risk for an explosion. The panic line  22  ordinarily allows excess gas to be vented to relieve strain on the rig  12  due to the elevated pressure. In the embodiment of  FIG. 1 , the panic line  22  may also couple to the catch tank  16  to prevent drilling fluid from exiting the apparatus  10  through a vent during blow out conditions. 
     With reference now to  FIG. 2 , the catch tank  16  is shown in more detail. The catch tank  16  comprises a tank body  30 , a base  32 , at least one inlet port  34 , a fluid line outlet  36  and a gas line outlet  38 . The tank body  30  as shown in  FIG. 2  is a cylinder. Alternatively, the tank body  30  may be a rectangular body or similar shape. The tank body  30  comprises a first end  40  and a second end  42  and is supported by the base  32 . The base  32  may comprise skids  44  for supporting the catch tank  16  and is preferably oriented for ease of transportation to and from sites where the apparatus  10  is required via truck, train car or other common carrier. 
     A mud-gas mixture enters the catch tank  16  at the at least one inlet port  34  located proximate a top of the first end  40  of the tank body  30 . Preferably, there are at least two inlet ports  34  located at opposing sides of the first end  40  of the tank body  30 . In a preferred embodiment, the inlet ports are approximately eight inches in diameter for connection to pipes common in the oil and gas industry. However, other diameters may easily be used with the catch tank  16 . The fluid line outlet  36  is located at a bottom of the tank at the second end  42  of the tank body  30  and allows drilling fluid to be removed from the catch tank  16  and processed for is further use in the drilling rig  12 . The drilling fluid may be removed via the fluid line outlet  36  using a fluid pump (not shown). The gas line outlet  38  is located near a top of the second end  42  of the tank body  30 . Preferably, the gas line outlet  38  comprises a connection to an eight inch pipe, as is common in the industry for the gas ignition line  18 . However, other diameters are anticipated by the present invention. 
     With reference now to  FIG. 3 , the catch tank  16  is shown with the inside of the tank body  30  visible. The at least one inlet port  34  comprises a director, such as closed end baffle  50 , a gas opening  52  and a fluid opening  54 . The director is shown as a closed end baffle, but one of ordinary skill can appreciate that the director may also be the inside of catch tank  16  or other equivalent structure. The gas opening  52  is located at a top end of the closed end baffle  50  while the fluid opening  54  is located at a bottom end of the closed end baffle. As shown, the catch tank  16  comprises two inlet ports  34 . One skilled in the art may appreciate that one of the inlet ports  34  may receive fluids from the panic line  22  ( FIG. 1 ) and the other from the mud-gas separator  14  ( FIG. 1 ). The inlet ports may be placed at the top of the tank, or alternatively through the bottom of catch tank  16 . An alarm may be provided to indicate flow through the panic line  22 . 
     With continued reference to  FIG. 3 , as fluid and gas enter the catch tank  16  through the at least one inlet port  34 , they contact the director, here closed end baffle  50 . Gravity causes drilling fluid to exit through the fluid opening  54 . Fluid is caused to settle within the tank body  30 . Gas exits the at least one inlet port  34  through both the gas opening  52  and the fluid opening  54 . One skilled in the art will appreciate that the gas entering the tank body  30  at the at least one inlet port  34  will exit through the gas line outlet  38 . Any drilling fluid entrained in the gas will fall out due to impact with the closed end baffle  50  and the time spent within the tank body  30  allowing the fluid to fall due to gravity. 
     One skilled in the art may appreciate that although the present invention has been described with respect to the preferred embodiment, various changes and modifications may be suggested to one skilled in the art, and it is intended that the present invention encompass such changes and modifications as fail within the scope of this disclosure.