Often on high pressure or high temperature wells, drillstem testing is considered too dangerous and thus bypassed. With the development of annulus pressure operated tools for offshore use come new pressure operated tools for offshore use come new techniques of drillstem testing that have proved to be safer than conventional testing methods. These tools and techniques can be used on high pressure and temperature wells on land to perform safe and efficient drillstem tests.
The annulus pressure responsive (APR) system of testing tools has been used offshore for years primarily because of its simple operation by varying annulus primarily because of its simple operation by varying annulus pump pressure. This operating method allows a pump pressure. This operating method allows a drillstem test to be conducted with a closed system (the rams are closed during the test), and no pipe rotation or manipulation is necessary to control the test. The possibility of a leak in the test string is reduced possibility of a leak in the test string is reduced and safeguards can be incorporated into the test string so that if a leak to the annulus occurs, the increase in pressure will trim a safety valve and close the well in. The full opening arrangement in the APR system also lends itself well to high pressure testing, allowing for greater drawdown to occur. The full opening feature also allows for perforating under-balanced, and treating through the tools.
Case histories will show how the APR system of testing tools can be utilized on land to achieve safer and more accurate test results.
As with all aspects of drilling and completion, drillstem testing tools and techniques have changed substantially with the increase of offshore drilling. New technology has spawned tools that allow for testing, treating, and wireline operations to be performed while maintaining needed safety. The most performed while maintaining needed safety. The most significant changes have been the introduction and perfection of annulus pressure operated testing tools, perfection of annulus pressure operated testing tools, whose offshore use dictates that they have easy operation, little or no flow restriction and built-in safe-guards to safely and effectively handle high pressures and volumes.
Onshore drilling has also advanced so that high pressure and volume reservoirs on land are being pressure and volume reservoirs on land are being explored and completed. The technology that has improved testing offshore can also be utilized onshore to yield safe and efficient tests.
This paper explores the theory, tools and techniques that surround the use of annulus pressure operated testing tools in onshore wells.
A drillstem test is a temporary completion of a well to gather reservoir data. This temporary completion and sampling operation is typically accomplished with the following assortment of tools:
Packer - A packer is used to seal offmovement of wellbore fluid to the face of the formation, since the hydrostatic pressure of the wellbore fluid will be relieved from the formation.
Tester Valve - A tester valve is run into the well in a closed position so the teststring will not fill with well fluid. When the tester valve is opened, the formation pressure encounters a pressure lower than its own; after the formation has produced some of its commodity, the tester valve can be closed to allow the formation to recharge itself.
Pressure/Temperature Recorder - A pressure recorder makes a record of the pressure versus time for both the flowing and recharging periods of the test. Temperature recorders are often run to record downhole temperature during the test.
Reversing Valve - A reversing valve is run primarily to reverse out any recovered primarily to reverse out any recovered formation commodities before tripping out the test string.