Integration of geophysical methods with reservoir simulation

Abstract

Time‐lapse seismic modeling was conducted for the Pikes Peak heavy oil field using the results from a reservoir simulation model. Cyclical steam stimulation (CSS) started in 1981 and continues to the present. A flow simulation model was constructed for the region around a seismic profile that was acquired in 1991 and repeated in 2000. The simulator was run from the start of production in 1981 through 2000. The porosity, saturation, pressure and temperature were extracted from the reservoir zone from the flow simulator for the early‐production condition in 1991 and almost 10 years later in 2000. The seismic response of the reservoir was computed using a fluid substitution procedure and seismic forward modeling. Comparing the results of 1991 and 2000 indicated that the gas saturation changes caused the largest change in the simulated seismic response. Seismic difference sections showed that thick zones of gas saturation caused more time delay in reflections below the producing zone by lowering velocity within the reservoir zone. Thin zones of gas caused reflection amplitude differences, but not much time delay differences. Temperature and pressure were also correlated with seismic changes, but not as quantitatively as the gas saturation. AVO analysis was used to map the gas distribution. The AVO mapped gas zones correspond reasonably well to the gas zones from reservoir simulation. The simulated seismic response difference section is similar in character to the observed difference sections.