A New Environmentally Friendly Technique to Extend the Limits of Transient Pressure Testing and Sampling Using Pipe Conveyed Open Hole Wireline Formation Testing Tools

Ayan, Cosan (Schlumberger) | Mishra, Vinay (Schlumberger) | Eriksen, Kåre-Otto (Statoil) | Van der Hoek, Jeroen (Statoil) | Thorne, Tyson (Statoil)



Transient well testing is one of the most critical components of reservoir evaluation due to its impact on a project's key economic parameters such as reserves and producibility. A conventional cased hole well test involves casing off the well, installing process equipment, completing the well perforating, flowing the well to surface and flaring the produced fluids. While the data acquired from conventional well tests is very useful; a large number of wells are not tested due to time, cost and regulatory constraints. In such situations with no well test, operators are obliged to take important decisions from a relatively small amount of reservoir information and hence take risks associated with subsurface uncertainties. To help reduce the development risks, a new pipe conveyed testing tool referred as Formation Testing While Tripping (FTWT) was developed. The new testing tool integrates a number of innovations allowing pumping large fluid volumes at higher rates with extended testing time and improved well noise control. This is done by circulating the produced fluids out of the wellbore during pumping out formation fluids. The new hardware can be combined with wireline sampling and downhole fluid analysis modules allowing to achieve overall well testing objectives; including collecting pressure transient data, real time fluid typing and capturing cleaner and larger volume fluid samples, while increasing the radius of investigation for better characterization of any reservoir heterogeneities compared to conventional wireline formation testing techniques.

In this paper, we introduce the new testing technique, which has recently been utilized in the Norwegian sector of the North Sea and offshore Canada. In one well, following the FTWT surveys, Drill Stem Tests (DST) were also conducted for comparison. The field examples and comparison with DST's indicated that the new method can provide valuable reservoir information while also showing its current limitations.