No abstract

Time-lapse 3D – or 4D – seismic data have been tried in several fields to date, with some good case studies published to demonstrate the utility of the 4D seismic information. While another 4D case study would be useful, this paper describes two novel aspects of a recent application in the Gulf of Mexico. First, the target reservoir contains a gas condensate fluid under primary depletion, so pressure, rather than saturation, changes create the observed 4D acoustic response. Further, the primary impact of the pressure change is to the fluid composition as the initially dense gas phase lightens as condensate drops out below the dew point. The result was a 2.8% change in acoustic impedance predicted in the feasibility study. Second, the 4D seismic result was used to constrain an optimized history-matching procedure, along with the production data. After describing the method used, the paper will discuss the changes to the reservoir model that resulted. While the results should not be considered unique, they do give some insight intothe structure of the reservoir that should be considered for optimal reservoir management.

No abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractTime-lapse 3D, or 4D, seismic has been tried in several fields to date, with some good case studies published to demonstrate the utility of the 4D seismic information. While another 4D case study would be useful, this paper describes 2 novel aspects of a recent application in the Gulf of Mexico. First, the target reservoir contains a gas condensate fluid under primary depletion, so pressure, rather than saturation, changes create the observed 4D acoustic response. Further, the primary impact of the pressure change is to the fluid composition as the initially dense gas phase lightens as condensate drops out below the dew point. The result was a 3.6% change in acoustic impedance predicted in the feasibility study.Second, the 4D seismic result was used to constrain an optimized history matching procedure along with the production data.After describing the seismic history matching method used, the paper will discuss the changes to the reservoir model that resulted. For comparison, some results using a production data only history matching procedure are also presented. While the neither set of history matching results should be considered unique, they do give some insight into the structure of the reservoir that should be considered for optimal reservoir management, and provide an indication of the impact of 4D information in history matching.