Zhou, Jinjuan (University of Houston) | Davydycheva, Sofia (Schlumberger) | Wang, Hanming (Schlumberger) | Habashy, Tarek (Schlumberger) | Frey, Mark (Schlumberger) | Barber, Tom (Schlumberger) | Abubakar, Aria (Schlumberger)
Gao, Guozhong (Schlumberger) | Alumbaugh, David (Schlumberger) | Zhang, Ping (Schlumberger) | Liu, Jianguo (Schlumberger) | Zhang, Hong (Schlumberger) | Levesque, Cyrille (Schlumberger) | Rosthal, Richard (Schlumberger) | Abubakar, Aria (Schlumberger) | Habashy, Tarek (Schlumberger)
This paper first summarizes the theory of providing resistivity images from cross-well electromagnetic (EM) measurements in metal cased holes. Metallic casing significantly attenuates EM signals. As a result, low frequencies are required to acquire useful EM signals in cased holes, which reduces the resolution within the inversion images. Comparison of casing materials shows that chromium steel casing attenuates the EM signals much less than carbon steel casing. Although cross-well EM technology can be successfully applied in open/fiberglassto- open/fiberglass and open-to-metal cased wells irrespective of the type of the casing, for casing-to-casing scenarios, cross-well technology at this point is limited to chromium-to-chromium scenarios.
Methods have been developed for the inversion of crosswell EM data in cased holes using data ratios to remove effects, or including the casing coefficient as an unknown in the inversion. This paper investigates the spatial and frequency-dependent sensitivity for different frequencies and inversion approaches for cross-well EM data acquired in cased holes. The applicability and limitations of these approaches are demonstrated on synthetic data simulating a water flood.