Wireline formation testing measurements have long been recognized as important to collecting essential information on the nature of the fluids in place, the pressure regimes, and the formation dynamic properties such as permeabilities. However, because previous techniques have required that the wireline tool be stationary for relatively long periods of time while testing the formation, especially in low-permeability zones, rig-time and tool-sticking considerations have limited data gathering.
In this paper we present a new generation of wireline formation tester dedicated to pressure only, whose design was geared towards decreasing rig time, reducing the risk of sticking, and improving the pretesting of tight formations. The pretest improvement uses a novel electromechanically controlled device that provides accurate control of the pretest flow rate down to extremely low values, enabling the pretest sequence to be tailored to the formation mobility. Combinability with the standard open hole tool string provides for even greater efficiency.
After a description of the tool performance and characteristics, we present the results of several months of field tests performed in a wide variety of environments, with emphasis on the gain in both operation time and quality of results. A particular focus is on pressure acquisition in an ultralow-mobility-mobility environment in which a previous generation of formation testers failed to consistently deliver results.