4D Seismic in the Deepwater – Challenges and Rewards

 David H. Johnston ExxonMobil Exploration Company

 Time-lapse or 4D seismic data has proven value in reservoir management, increasing reserves and recovery by locating bypassed and undrained hydrocarbons and optimizing infill well locations and flood patterns. 4D seismic can also decrease operating costs by reducing uncertainty in the reservoir geologic model and flow simulation, optimizing completions, and minimizing the number of dry holes.  4D is simply the use of multiple seismic surveys shot over a producing field. Changes in the seismic response typically occur because of production-induced changes in saturation and pressure. Successful 4D projects have been carried out in a wide range of geographical areas, geological settings, and depletion scenarios.

 To maximize the value of a 4D seismic project, planning for 4D is a critical part of an overall field lifecycle strategy. In exploration, assets can be screened for potential 4D application. Early in development planning, 4D seismic models based on reservoir flow simulations and geologic models are used to estimate the magnitude and interpretability of the 4D response, evaluate optimal survey repeat times, and assess potential business impact. Once the field is under production, effective 4D project execution requires collaboration among asset team geoscientists, engineers, and field operations with geophysical acquisition and processing specialists.

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