Resistivity Anisotropy as a Decision-Making Tool: A Case Study From Egypt

This reference is for an abstract only. A full paper was not submitted for this conference. When BP drilled the offshore Nile Delta well, Ruby-2, they encountered a sequence of thinly laminated shaly sands. Neither LWD nor conventional wireline resistivity logs gave clear indication of hydrocarbon presence, and only a small crossover on the neutron and density logs showed the possibility of the presence of gas. Fortunately, BP also ran a multi-component induction device, allowing the measurement of vertical resistivity in addition to the conventional horizontal measurement. The electrical anisotropy measured by this tool gave a clear indication of the presence of hydrocarbons in the laminated formation and made the decision to test the interval a foregone conclusion. Following the successful test, the data recorded also allowed the petrophysicists to evaluate the formation with greatly reduced uncertainty, and made it possible to distinguish between productive laminated intervals and non-productive zones where formerly laminated sequences have been disturbed by bioturbation and slumping. This paper reviews the technology behind the tool and the tensorpetrophysical model used in the interpretation and uses examples from the Egypt well to illustrate the various benefits of using these techniques. The paper also shows confirmation of the techniques by comparison with core and imagedata.