Abstract
The CSEM method, which is frequently used as a risk-reduction tool in hydrocarbon exploration, is finally moving to a new frontier: reservoir monitoring and surveillance. In the present work, we present a CSEM time-lapse interpretation workflow. One essential aspect of our workflow is the demonstration of the linear relationship between the anomalous transverse resistance, an attribute extracted from CSEM data inversion, and the SoPhiH attribute, which is estimated from fluid-flow simulators. Consequently, it is possible to reliably estimate SoPhiH maps from CSEM time-lapse surveys using such a relationship. We demonstrate our workflow’s effectiveness in the mature Marlim oilfield by simulating the CSEM time-lapse response after 30 and 40 years of seawater injection and detecting the remaining sweet spots in the reservoir. The Marlim reservoirs are analogous to several turbidite reservoirs worldwide, which can also be appraised with the proposed workflow. The prediction of SoPhiH maps by using CSEM data inversion can significantly improve reservoir time-lapse characterization.
Highlights
The controlled-source electromagnetic (CSEM) method is a risk-reduction tool for hydrocarbon exploration that is complementary to the seismic method [1]
We show that the anomalous transverse resistance (ATR), a key parameter in defining the CSEM response of a given reservoir, exhibits a strong linear correlation with the SoPhiH maps obtained from the fluid-flow simulations
We presented a CSEM data interpretation workflow for time-lapse reservoir monitoring purposes
Summary
The controlled-source electromagnetic (CSEM) method is a risk-reduction tool for hydrocarbon exploration that is complementary to the seismic method [1]. An exception is provided by the long-term study of [15], where they investigated 110 years of CO2 injection in a deep saline aquifer for storage purposes This situation is favorable for the CSEM method, as the target’s resistivity increases with time, yielding stronger anomalies. After over 30 years of production and seawater injection, long-term time-lapse CSEM monitoring would still be feasible for these mature fields To confirm this hypothesis, we developed an iterative workflow (Figure 2) that includes reservoir flow simulations in a realistic Earth model to produce an updated Earth model, forward modeling of the synthetic CSEM response, inverse modeling of the synthetic CSEM response, extraction of relevant EM attributes at the reservoir interval, and their correlation with petrophysical parameters. The proposed workflow can be implemented in similar reservoir settings worldwide
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