Autonomous Formation Pressure Test Process for Formation Evaluation Tool

摘要

A formation tester places an isolation device, preferably a probe, in fluid communication with a formation to determine formation pressures. The tester's controller uses a pressure pre-test process to autonomously control operation. The controller measures drawdown pressure and interval as the tester draws down pressure in flowline coupled to the probe. If the drawdown pressure indicates a dry test has occurred, the process is aborted. Otherwise, the controller measures buildup pressure and interval by allowing buildup of pressure of the flowline. The controller permits this to continue until the interval is longer than the drawdown interval and/or until a rate of the buildup falls below a predetermined rate. If the buildup pressure is too tight relative to the drawdown pressure, the controller aborts the test. Eventually, the controller measures a final buildup pressure when the buildup terminates. A new drawdown rate and volume can be determined for subsequent formation tests.

主权项

1. A formation tester, comprising:
an isolation device disposing in fluid communication with a formation; a drawdown volume being adjustable and in fluid communication with the isolation device; one or more sensors monitoring pressure in fluid communication with the isolation device; and a controller operatively coupled to the one or more sensors and the drawdown volume and preconfigured to test each of one or more stations of the formation with at least two autonomous drawdowns and buildups, the controller configured to:
perform a first of the autonomous drawdowns toward a first preconfigured volume of a total available volume with a first preconfigured flow rate at one of the stations to obtain a first drawdown pressure;perform a first of the autonomous buildups at the one station after success of the first autonomous drawdown to obtain a first buildup pressure;determine a second volume as a fraction of the total available volume remaining from an actual volume used in the first drawdown;determine a second flow rate after success of the first autonomous buildup from the first preconfigured flow rate scaled by a ratio based on a difference between the first buildup pressure and the first drawdown pressure;perform a second of the autonomous drawdowns toward the second volume with the second flow rate at the one station;perform a second of the autonomous buildups at the one station after success of the second autonomous drawdown to obtain a second buildup pressure;compare the first buildup pressure measured in the first autonomous build up to the second buildup pressure measured in the second autonomous buildup; andproceed with operation of the formation tester based on the comparison.