A Rock Physics Based Time-Lapse Feasibility Workflow Calibrated to CoreMeasurements Which Incorporates Both Fluid Changes and PressureDepletion

摘要

Rock physics analysis is a useful tool in time-lapse seismic feasibility studies and can help to assess theeffect of pressure and saturation changes on the elastic parameters which the seismic data is sampling andhence the probability of success of a 4D seismic survey.Calibration using velocity measurements made ondry core data at varying pressure conditions allows for forward modelling of the expected seismic responseat different effective pressures as well as different hydrocarbon saturation levels.The step of forwardmodelling the pressure changes is performed less frequently and in a less well calibrated manner than that ofchanging the hydrocarbon saturation as there is often no core data analysis performed at different pressures.In this study we show that incorporating pressure effects produces non-negligible changes to the elasticproperties of the reservoir rock.Changes of up to 10% and 8% to acoustic and shear impedance respectivelyare observed in the most prospective reservoir interval when the pressure effect is included.Such changeswould be detectable by high quality 4D seismic data.The authors recommend including the pressure changedata whenever possible in 4D rock physics modelling.