Optimization of Multivariate Production-Injection System for Water-Alternating-Gas Miscible Flooding in Pubei Oil Field

摘要

The first Water-Alternating-Gas (WAG) miscible flooding project, Pubei oil field in Xinjiang, was put into production and scheduled to initially inject miscible gas as well as water at the early development stage. With consideration the specialty of the WAG process, optimization of multivariate productioninjection system (PIS) is the Gordian knot of improving the reservoir benefit as well as extending the reservoir life. In general, the production history of a reservoir can be predictedrnby integrating a reservoir model, and a production model including a wellbore model and a choke model. Changes in any production and/or injection parameter will cause changes in the predicted production and/or injection history. Well-to-well tracer results were used to modify thernreservoir model and evaluate efficiency of WAG during the field development, and novel integrated concepts and methods were proposed to couple the reservoir model with well model including both injectors and producers. The genetic algorithm is shown to be both stable and efficient when used to optimize the multivariate PIS with different constraints. It is shown from field applications that reasonable measures can be adopted for globally optimizing production and injection at thernany stage of the field life, and that parameters including bottomhole flowing pressure, reservoir pressure, injection pressure, oil rate, gas-oil ratio, water-cut, etc. were controlledrnand adjusted in an optimized range.