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The decision of any data acquisition should always involve a cost - benefit analysis. While cost identification is usually easy, the value gained with new data is specialy difficult when there are mostly indirect benefits. This is the case of 4D seismic projects where the main contribution is to reservoir production management. Recently, the interest on 4D seismic and the number of such projects have increased significantly. Despite of the high cost, there is a lack of robust and systematic process to evaluate their value. Bp TT faced this challenge when analyzing a Life of Complex Seismic (LoCS) project for multiple gas reservoirs in the Greater Cassia Complex, located in the Columbus Basin, Trinidad and Tobago. This Complex comprises many producing and future development fields including Amherstia, Immortelle Parang, Kapok, Cannonball and Cassia.A significant fraction of present and future potential reserves of several Tcf is under shallow gas, which has detrimental impact on seismic image quality. Such condition required consideration of expensive 4C OBC (Ocean Bottom Cable) seismic acquisition options. Additional benefits from 4D seismic for monitoring dynamic reservoir performance could be foreseen with a permanent installation. A robust and systematic value of information study was developed as part of the LoCS project in order to support the decision about the 4D acquisition options. This work describes the Decision Tree process used in the LoCS value of information study as well as discusses the main results used by bpTT to make a based decision about the acquisition program. |
