Accessing the Application of 4-D Seismic in Block 14, Angola

Peter Mitchell, Larry J. Sydora, and Peter Nevill
Chevron Corporation, San Ramon, CA

Over the last 10 years 12 fields with over 1.5 Billion Barrels of reserves have been discovered in Block 14, offshore Angola. Exploration in the block has come to an end and the focus is now on development and production. Part of the development and reservoir management plan for each field is accessing the technical and business feasibility of 4-D seismic. From the technical perspective the rock physics, fluid properties, reservoir models, production profiles are reviewed and integrated to analyze the change in seismic response over time. This is then evaluated against previous seismic acquisition, acquisition constraints such as obstructions, localized near surface anomalies and signal to noise, to determine if changes in amplitude can be detected. This is then used to recommend acquisition scenarios and timing appropriate for maximizing the effectiveness of the 4-D. From a business perspective the Value of Information (VOI) is evaluated relative to field maturity, impact on future production, development scenarios, and risk management. The VOI screens the 4-D potential in terms of economic return over the life of the project. The combination of both perspectives is integrated into the Reservoir Management plan with a view to supplying a "road map" early in many of the projects on if, how and when 4-D should be utilized. This methodology is demonstrated using a number of examples from the Block 14 fields that are in various stages production life cycle.

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