Wells – Submerged well – Testing
Patent
1994-03-25
1996-01-16
Schoeppel, Roger J.
Wells
Submerged well
Testing
166324, E21B 3410
Patent
active
054840228
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a valve for use in a drill string for pressure testing tubulars and downhole test equipment for use with tubulars.
Particularly, but not exclusively, the invention relates to a valve for testing tubulars in a cased hole which has a permanent packer fitted.
BACKGROUND OF THE INVENTION
In order to test a well with a permanent packer set inside a casing, a test string is required to be made up for running in the well. A test string typically includes, but is not limited to, the following components, in order, from the bottom up. A bullnose or wire-line re-entry guide, a packer seal assembly, a locator no-go, a tubing test valve, various testing and safety valves and tubulars of sufficient length to reach the set casing permanent packer. Because the permanent packer is pre-set and the packer forms part of the casing downhole, the test string length is determined by the following factors; tubing length and size--each length being individually measured, and the temperature and stretch of the tubing in the well. The test string length must correspond to the packer depth almost exactly.
To try and pre-calculate the amount of pipe required to exactly enter a permanent packer, and be correct within inches, is impossible in practice. The standard technique used is therefore to calculate the pipe requirement approximately, and then enter the packer bore until pipe will not enter any further. This is the point when the locator no-go abuts the top of the permanent packer and this can be detected on the drilling rig. From this known point and a second known point which is the location of the formation top surface, i.e. the sea bed or land surface, the complete test string can be spaced out as required. This is typically done by painting a section of pipe white and closing a set of pipe rams contained in the drilling BOP stack to give it an exact mark. Using this marking the pipe can be spaced out as necessary to include well test equipment such as a subsea test tree and other tools. During this space-out the string is run-in until the locator no-go abuts the top of the packer; the string is then withdrawn several feet, for example 10 feet from the packer, so that there is a good seal between the packer seal assembly and the interior surface of the packer called the polished bore receptacle (PBR). This packer seal assembly includes alternate bands of metal and elastomer, usually "VITON" (trademark) seals, so that slight movements relative to the PBR do not effect the seal in between the tool and the permanent packer.
Existing tubing test valves allow the mud/fluid contained within the casing to freely enter the test string as the test string is lowered downhole by adding each section/length of tubular. A typical tubing test valve currently used is the Halliburton TST (Tubing String Tester) valve which allows the DST string to be pressure tested while running in the hole. The Halliburton TST valve includes a flapper valve and spring so that when running in the hole the flapper valve opens and allows the test string to fill up. When the test string is stationary the flapper valve is held closed by the spring. The string can be pressure tested as many times as required while running in the hole. With valves of this type the tubulars can be internally tested by pumping down inside the test string on top of the tubing test valve. The pressure is monitored at the surface and pressure testing verifies the pressure integrity of the connections of the tubulars and assemblies above the tubing test valve. Therefore, the pressure test procedure can be repeated as many times as desired until all tubulars are added to give the full length of the test string. As described above, the full length of the test string is determined by the space out from the locator no-go. Once the full length of the string has been determined then various test tools can be added to the string as required in order to permit safe testing of the well.
Therefore, the procedure is to run-in to determine
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Coutts Graeme F.
Edwards Jeffrey C.
Exploration & Production Services (North Sea) Ltd.
Schoeppel Roger J.
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