A great portion of the world’s oil reserves is contained in naturally fractured reservoirs. As the conventional oil and gas reservoirs have become significantly depleted whereas energy demand is sharply increases, NFRs play an important role in oil exploration and makes a large contribution toward oil and gas production worldwide. However, characterization of fractured reservoir is very complex as compared as conventional reservoirs. Lacking of experiences during production stages may quickly destroy entire reservoir. Therefore, the successful case studies as well as failure lessons should be highlighted for improving recovery efficiency in such complex reservoirs.
This paper aims to introduce two historical case studies of successful development plan for giant fractured granite basement reservoirs in Viet Nam. These reservoirs contain huge hydrocarbon resources in basement source rock and present a unique geological characterization, very high heterogeneity, high temperature and closure stress. A detailed geological understanding of the reservoir, along with a creative reservoir simulation, is needed to determine the optimal recovery method for these reservoirs. These are the keys to having a successful operation, as well as reducing uncertainties and achieving the most efficient of oilfield management.
With a large database collected from over twenty years of production period of over 215 wells, the authors developed a workflow for integrating between static and dynamic data. The geological characterization of two typical basement reservoirs was thoroughly analyzed to figure out their effect on recovery schemes. A new approach for building geological model by artificial neuron network technique was introduced, and these integrated results have been served as input data for simulation with IMEX in CMG simulator. Based on the reservoir modeling, we proposed a promising method for improving oil recovery factor by optimizing the well network locations, application of horizontal well and gaslift. From our historical experiences, the authors introduce the most appropriate method for overcoming the challenge of waterflooding operation and stimulation for fractured basement reservoirs.