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 techniques of drillstem testing that have proved to he safer than conventional testing methods. These tools and techniques can he 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 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 and safeguards can be incorporated into the test string so that if a leak to the annulus occurs, the increase in pressure will trip 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.