Assessing the effect of geological uncertainty on recovery estimates in shallow-marine reservoirs: the application of reservoir engineering to the SAIGUP project

Reservoir management is a balancing act between making timely operational decisions and the need to obtain data on which such decisions can be made. There is a further problem: estimates of recovery for prospective development plans are subject to uncertainty because of the uncertainty of the geological description within the simulation model. The SAIGUP project was designed to analyse the sensitivity of estimates of recovery due to geological uncertainty in a suite of shallow-marine reservoir models. However, although it was generic, it had the hallmarks of active reservoir management, because those members of the team responsible for deriving the notional development plans for individual models via reservoir simulation, and computing the recoveries, had to work in parallel with others under time and budget constraints. This paper describes the way the reservoir engineering was carried out to achieve these objectives, the assumptions made, the reasoning behind them, and how the principles could be used in other studies. Sample results are also presented, although the bulk of the results are presented in other papers in the project series. One surprising result was that faults that impede flow can improve recovery. The underlying physical explanation for this behaviour is provided.