Measuring and testing – With fluid pressure – Pipe
Reexamination Certificate
2000-11-10
2002-08-13
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Pipe
C073S040700
Reexamination Certificate
active
06430990
ABSTRACT:
FIELD OF INVENTION
The present invention generally relates to the field of drilling oil and gas wells and, more particularly, relates to an apparatus for testing the integrity of pipe segments, especially the connections between joints of pipe.
BACKGROUND OF INVENTION
In the oil and gas industry, many sections or lengths of tubular pipe are commonly strung together to form pipe strings or tubing strings often measuring many of thousands of feet in length. These pipe strings are employed in oil and gas wells to convey oil and natural gas from their subsurface environments to the surface of the wells. Typically, the pipe string is inserted within a string of larger diameter pipe known as casing. The pipe casing is intended to support and seal the walls of the well bore hole.
Because the oil and gas in the pipe string is typically conveyed to the surface of the wells at high pressures, the pressure integrity of the pipe string must be maintained. Oil or gas escaping from the pipe string into the annulus between the casing and the pipe string due can create a dangerous situation that may create an explosion, loss of the well, or both, and cause the loss of the oil and gas, environmental pollution, and injures to the personnel at the well site.
Typically, the segments of pipe that make up the pipe strings are jointed together by treaded connections, each segment of pipe having a threaded male connection at one and a threaded female connection at its opposite end to join and seal adjacent pipe segments together. A potential point of leakage or threat to the pressure integrity of the pipe strings is at the connection point, i.e., the threaded connection, between the pipe segments that make making up the pipe strings. Consequently, measures must be taken to guard against sealing deficiencies, leaks and other imperfections that threaten the pressure integrity of the threaded connections making up the pipe strings.
The connections between the segments of pipe forming the pipe string are typically tested by sealing the bore of the pipe string at points above and below the threaded connections between the pipe segments and introducing a fluid, either fluid or gas, under pressure into the sealed bore check for leaks. Efforts have been made to provide pressure testing tools to facilitate testing of the pressure integrity of pipe strings. One such device is that described in U.S. Pat. No. 5,563,336 to Applicant. In that patent applicant describes a tubular apparatus inserted into the pipe string, across the area or joint to be tested. The apparatus has a gas sealing line used to supply sealing gas under pressure to move upper and lower pistons, essentially simultaneously, that expand resilient seals against the internal walls of the pipe string. In that manner a test chamber, defining the space between the resilient seals and the pipe string wall, is created for the subsequent introduction of a test gas to check for leaks. When the testing is completed, gas pressure in the sealing gas line is reduced causing the retraction of the upper and lower pistons, again essentially simultaneously, releasing the seals of the apparatus.
A problem associated with the aforementioned tools and testing methods is the risk of a “tool kick” or rapid displaced of the tool caused when the high pressure testing gas in the testing chamber is released downward into the pipe string. “Tool kick” is often caused when the seal produced by the testing tool's lower sealing piston is broken before the seal produced by the tools upper sealing piston, even if only momentarily. The rapid release of pressurized gas down the pipe string may displace the tool upwardly with tremendous force creating a risk of injury to the personnel performing the pressure test and damage to the testing assembly, all increasing the costs and risks of the pressure testing.
Another problem associated with the present testing tools and methods may arise during the testing of connections of long pipe strings running into the well bore. Drilling fluids or mud is typically used to contain the surfaces of the bore hole and the down hole gas pressure as the pipe string is run into the bore hole. The drilling mud or fluids often begin to flow upwards through the tubing as each pipe segment is lowered into the well bore. The drilling fluids can cause the testing tool to float above the fluid making the correct or desired placement of the tool difficult. Even if the tool is correctly placed, the drilling fluids may surround the tool and be contained within the test chamber. The drilling fluid may then restrict the flow of testing gas or block the leak path of the testing gas causing the connection to appear to be leak free. When the drilling fluid is removed from the pipe string during production, the undetected leak can cause problems with the well.
Consequently, a need exist for improvements in testing tools that will reduce the risk of “tool kicks” as well as the incidence of unreliable pressure tests caused by the presence of drilling fluids in the area of pipe string being tested.
SUMMARY OF INVENTION
The present invention provides a pressure testing apparatus and method designed to satisfy the aforementioned needs. The pressure testing apparatus of applicant's present invention is comprised of a generally cylindrical tool having upper and lower piston driven sealing means or packers for insertion into a pipe string. For testing purposes the tool will be placed in the pipe string so that the area to be tested, typically a threaded connection, will be positioned between the upper and lower packers. The packers are used to create a test chamber in the annulus between the tool and the inner wall of the pipe string defined by the upper and lower packers.
A novel feature of applicant's present invention is that the upper and lower packers can be set and released independent of each other. In the preferred embodiment the lower packer is set with a piston driven by fluid pressure created in a pressurized fluid line, water being the preferred pressurized fluid, and the upper packer is set with a piston driven by gas pressure created in a pressurized gas line comprised of the testing gas.
During a typical testing operation, as the pipe string is being assembled, two segments of pipe with threadably connecting ends, each of an average length of approximately thirty feet, are made up, one length above the other, on the rig floor by means of the rig's power tongs. The testing apparatus of applicant's present invention is then inserted into top end of the upper pipe segment, through the upper segment and into the lower pipe segment so as to place the lower packer of the testing apparatus at a point below the connecting end of the lower segment.
Once the lower packer is positioned, the connection between the upper and lower pipe segments is made up, i.e. the ends of the pipe are threaded together, at the desired torque by means of the rig tongs. The lower packer is set against the interior wall of the lower pipe segment below the connection point by means of its fluid pressure piston and the upper packer is set against the interior wall of the upper pipe segment by means of the piston actuated by the pressurized helium. Typically, the upper and lower packers are set at the same time. However, as well conditions dictate, it may be desirable to set the lower packer prior to setting the upper packer. When the upper and lower packers are set in the described manner, whether at the same time or sequentially, the annulus area between the upper and lower packers and the interior wall of the pipe string defines a test chamber. Once the test chamber is formed, pressurized helium gas, evacuated from the interior of the tool through a gas orifice, fills the test chamber space.
After the connection is made up, a helium containment sleeve is placed on the pipe string around the outside of the connection to be tested. Within the helium containment sleeves are helium sensors design to detect the presence of helium that may be trapped within the containm
Garber Charles D.
Mallet Ronald J.
Stagg William W.
Williams Hezron
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