Reconciling Time-Lapse Seismic and Production Data Using Streamline Models: The Bay Marchand Field, Gulf of Mexico
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AbstractOne of the goals of reservoir characterization, particularly in mature reservoirs, is to identify unswept regions containing high oil or gas saturation for targeted infill drilling or enhanced recovery. Given the dense spatial sampling associated with time-lapse seismic surveys, there is a potential to map detailed interwell saturation changes in the reservoir. However, seismic attributes such as travel time and amplitude changes are indirectly related to reservoir saturation changes. Reservoir production data such as water-cut response at wells are related directly to saturation variations. An effective integration of the two forms of data is necessary to reliably characterize saturation distribution and still remains an important unresolved problem. A fundamental difficulty is the burden of reservoir simulation: use of conventional finite-difference reservoir simulators render coupled inversions of seismic and production data computationally challenging.Recently streamline-based flow simulation models have demonstrated significant potential in integrating dynamic data into high-resolution reservoir models. The streamline approach has relied on computing and matching travel time of fluid fronts at the wells and can be naturally extended to directly relate time-lapse images of a multiphase front to reservoir properties. In particular, saturation, porosity, and pressure variations in the reservoir will induce changes in seismic attributes such as amplitude or the travel time. These changes can be incorporated into the streamline-based history matching using appropriate rock physics models. The result will be interwell saturation maps that are constrained by both production and seismic data. A key advantage of our approach will be its computational efficiency that makes it ideally suited for large-scale field applications.At the Bay Marchand Field in the Gulf of Mexico both time-lapse seismic and water-cut observations are integrated to infer permeability variations within the reservoir. Some 40 years of historic production data are available at the Bay Marchand Field. In all, water-cut data from eight wells are used to constrain permeability variations in the reservoir. The streamline-based inversion is able to match the observations in 15 iterations, approximately four hours of computation for this 20,000 cell 3D model. The time-lapse seismic data are related to the reservoir saturation and pressure changes through Gassmann's equation and laboratory derived relationships. The time-lapse seismic data reveal large-scale amplitude variations that appear to correlate with saturation changes in the reservoir.
