Fluids, such as oil, gas, and water, can move within a reservoir over geological time. This talk will show how recognising these processes and incorporating them into analysis can greatly improve reservoir characterization and provide powerful insights to optimise development plans. I will use 3 very different examples to illustrate this.
Firstly, a deepwater oil field, that had long been considered an “ugly duckling” was re-evaluated incorporating knowledge of historical fluid movement which had created compositional grading. The new analysis revealed better connectivity, higher recoverable oil volumes and a previously unrecognized tar mat, which demonstrated that producer locations should be higher on structure and the potential need for a waterflood.
Secondly, the Sunrise gas field in the Timor Sea was reassessed with the knowledge of historical advective gas mixing. This showed that Sunrise, previously thought to have a high risk of compartmentalization, was actually well connected both vertically and laterally. This analysis changed the number and locations of planned development wells, significantly reducing the potential development cost.
Finally, in the Alberta Oil Sands, analysis showed that the redistribution of “solid” bitumen and water had occurred as a result of biodegradation. This explained the puzzling water mobility and “upside down” transition zones. This knowledge is important in predicting the lateral movement of steam/heat needed for the optimum design of thermal oil recovery.
The movement of fluids within a reservoir over geological time happens more often than is commonly thought and is an under utilized tool for reservoir characterization. It is particularly valuable for offshore development where information is sparse. The most important key to using it is simply asking the question "could it have occurred?"
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