Experience with Crosswell Electromagnetics (EM) for Waterflood Management in Oman

Abstract

TX 75083-3836, U.S.A., fax +1-972-952-9435. AbstractBeginning in 2003 Petroleum Development Oman (PDO) began testing the crosswell electromagnetic method for waterflood monitoring in Oman. The tomographic method, which determines interwell resistivity from inductive EM signals, is well suited for tracking injected water volumes, especially when this fluid is a low resistivity, high salinity brine.The method was applied in two Omani oil fields for tracking injected water. In the first field several vertical well pattern pilots were established to measure water flood sweep efficiency in two zones of a shallow, but relatively thick, multi layer reservoir. In the shallow zone a two year monitoring program revealed that much of the injected water had bypassed the reservoir, likely escaping through high permeability streaks. In the deeper pilot the EM results showed an excellent interwell sweep but some leakage to the overlying formation. For the second field the method was applied in existing widely-spaced barefoot injection wells. In this old line drive flood we wished to image the residual oil saturation and injected water volumes. In this case the resistivity anomalies in this mature water flood were fairly subtle. Interwell formation heterogeneity could only be revealed by calculating resistivity differences between the initial or background model and the image after inversion. One of these difference images revealed that a significant oil bank remained adjacent to the central producer.The overall experience with the crosswell EM tomography revealed that this technique can have great value in imaging water flooding. Drawbacks include the costs of installing special monitoring wells that are required under some conditions and the low resolution that is obtained in cases where the length of the survey interval is short relative to the well spacing. A good reservoir model is required in order to use constraints that are required for steering the crosswell EM inversion.

Applications of tomography in the oil-gas industry – Part 2

“…This process employs an iterative procedure to update and minimize the differences between the measured data and the modelled responses in a least-squares sense (Abubakar et al, 2005;Li, Abubakar, Li, Pan, & Habashy, 2010;Wilt & Alumbaugh, 2014). The resulting resistivity distributions are used to track inter-well fluid movements (Mieles et al, 2009;Wilt et al, 2012).…”

Enhanced characterization of reservoir hydrocarbon components using electromagnetic data attributes

“…We focus our analysis on the impact of the EM data on the recovery of the individual hydrocarbon components. The work differs both in terms of focus and technique from previously conducted studies [49]- [52]. We assumed that Archie's parameters are uncertain, spatially heterogeneous, estimated within the history matching process, and investigated the impact of EM data on history matching the individual hydrocarbon components, which has not been investigated previously.…”