Methods For Analyzing Formation Tester Pretest Data

摘要

Methods are disclosed for processing, in real-time, pressure data acquired with a formation tester during a pretest to quickly establish the quality of the measurement being conducted. The methods can optimize pressure measurement operations by assessing whether it is desirable or not to wait for the formation tester flowline pressure to equilibrate to the sandface pressure. In one embodiment, a determination is made as to whether the pretest succeeded in establishing hydraulic communication between the formation and the flowline by comparing the pressure signal with a simulation of the pressure behavior corresponding to a false buildup during a dry test. In another embodiment, a determination is made as to whether the pretest succeeded in isolating the tool flowline and the formation from the wellbore by using the pressure signal to estimate the sandface pressure during buildup over time, and to compare the estimated sandface pressure signal with the borehole pressure.

主权项

1. A method for conducting a pretest with a formation tester tool located in a borehole traversing a formation, comprising:
a) obtaining a dry buildup pressure curve (Pbu,dry(t)) for the formation tester tool; b) conducting a drawdown procedure followed by a buildup with said formation tester tool; c) measuring flowline pressure (Pfl) of the formation tester tool over time during the buildup to obtain flowline pressure values; and d) comparing said flowline pressure values over time with said dry buildup pressure curve, and if a difference in pressure values of said flowline pressure and said dry buildup pressure is below a first threshold value for a first defined period of time, discontinuing the pretest, and otherwise continuing the pretest.