Production strategy for multilayer reservoirs

Abstract

The problem addressed here is the challenge of determining the best production strategy for multilayer reservoirs which varies from field to field as well as from well to well. Commingled production strategy is one of the most commonly used for several multilayer wells. However, there are some limitations to this method. Mostly, when very complex multilayer wells which contain different types of fluid in each productive layer are identified, the selection process of production approach is basically trial and error and later found to be a poor choice. One attempted solution to choosing the optimal production strategy is using numerical reservoir simulation. In this study, we used reservoir simulation to compare the performance of four different production strategies for different combinations of types of fluid present in a two-layer system. Strategy 1 in which the fluid is produced from two layers simultaneously is the best production approach when oil is present in the top and bottom layers. Strategy 2 in which the fluid is produced from one layer at a time starting with the bottom layer is the best production approach when reservoir fluid at the top layer is gas while fluids present in the bottom layer can vary from oil, gas&oil, gas&water and oil&water. Strategy 3 produces fluid from one layer at a time, starting with the bottom layer. When the production rate decreases to half of the original rate, the two zones are produced in a commingled fashion. Similar to strategy 1, strategy 3 is also the best production approach when oil is present in the top and bottom layers. Strategy 4 is similar to strategy 3 but starting with the top layer. This strategy is the best production approach when oil is present in the top layer and gas&water in the bottom layer. This approach can delay water production and sustain reservoir pressure.