4-D Seismic in the Deepwater — Challenges and Rewards

David H. Johnston
ExxonMobil Exploration Co., Houston, TX

Time-lapse or 4D seismic data can increase reserves and recovery by locating bypassed and undrained hydrocarbons and by optimizing infill well locations. 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.

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.

ExxonMobil’s experience in West Africa and the Gulf of Mexico demonstrates that the deepwater production environment presents unique opportunities and challenges for 4D projects. Issues range from the impact of surface facilities on data quality to contending with ongoing field operations. In addition, aggressive drilling schedules dictate a rapid turnaround of 4D data. But these fields have high drilling and well intervention costs and 4D seismic may be the only available field-wide reservoir surveillance tool. This presentation shows how ExxonMobil uses 4D seismic technology in deepwater reservoir management and discusses some of the challenges faced in its application.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery