Mature Field Rejuvenation Through 4D Seismic Application: Experience From Study To Execution

Abstract

Time-lapse or 4D methodology, that uses repeated 3D seismic surveys to monitor fluids saturations changes in reservoir, is a recommended tool for reservoir management in particular in deepwater fields where additional investments must be carefully evaluated due to the associated costs.This paper presents a real case of a successful rejuvenation project of a deepwater field in West Africa, supported by integrated 4D and reservoir 3D studies. The field, located in 800 m of water depth, has been producing for 10 years with a rate currently equal to the half of the FPSO nameplate capacity. In 2010 a seismic acquisition specifically designed for 4D purposes was executed and, integrated with the historical production data, led to a revision of the levels' potentiality. Reservoir barriers and fluids movements, water and gas in particular generated by the injection, have been modeled based on 4D acoustic impedance differences and were supported by history matching on the dynamic model. The strongly integrated approach supported a volumes in place revision that drove a sidetrack campaign on two wells to reach undrained areas. The integrated study highlighted also the possible risk of water encroachment on one of the targets of the two wells, that was therefore considered as a secondary target in the sidetrack plan. The result of the drilling campaign, combined with near field exploration, confirmed the expectations and contributed to double the production back to the initial peak plateau rate. Lesson learnt on this successful integration among disciplines are presented.