The goal of all history matching for the reservoir models is to generate accurate predictions. There is also an assumption that a better history match should lead to a more accurate prediction, which can lead an asset team to concentrate on a single model.

The assisted history match techniques allow us to generate multiple models that satisfy the surveillance 1 , and understand a range of outcomes for a set of models. What we need is to provide assurance that we are searching correctly for the range in outcomes, to understand the interaction between uncertainty, surveillance, and the business decision.

This paper describes an example for the Mahogany field in Trinidad, which is mainly gas with a thin oil rim. As the reservoir pressure is decreasing, there is a window of opportunity to drill an additional well.

The first task is to determine the correct value of a new gas well, to protect against water encroachment. The Mahogany field used BP's Top Down Reservoir Modeling (TDRM™) to test a hypothesis - is it possible to find models that match history, and have certain key features in the future? In this case we are specifically looking for a scenario with water at the existing gas well locations. Since the system is generating discrete models, we can then test which new gas well locations would mitigate the water.

We've also been able to use an idea from our Alaskan operations, and consider water injection with a dump flood. The appraisal of the water injection has been performed using computer assisted depletion planning tools (TDDP2 ) to assess the best location and strategy for such a well.

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