Fracture Stimulation in Waterflood Fields of Western Siberia: A Case Study of WaterPrediction and Oil-Production Optimization Using Multiphase Reservoir SimulationTechniques

摘要

Hydraulic fracturing in Western Siberia is continuallyevolving into larger and more aggressive fracture treatments toachieve higher conductivity than conventionally planned. Atthe same time some of the fields that have been waterfloodedfor 20 years or more for pressure maintenance, have becomehighly water-saturated. In the past, stimulation treatmentswere designed based on old log interpretations showing watersaturation at original conditions and post-fracture waterproduction was frequently under-estimated, while overestimatingoil production.A comprehensive study was conducted into the water-flooding pattern of a Western Siberia oil field, and water-cutmaps were generated to determine which areas of the fieldwere more water-saturated. This study included a statisticalanalysis of the effect of various fracture parameters on thepost-fracture water-cut. Also the relationship between nearbywater injectors and post-fracture water production wasanalyzed. It was found that injectors in a NNW proximity tothe fractured well contributed higher post-fracture water rate.Generally, fractures grow in this direction, which is themaximum principal stress orientation across much of theWestern Siberian Basin. This paper presents and discusses thestatistical approach we developed.A new method of predicting post-fracture productioninvolving a multi-phase reservoir simulator, was employed.The water and oil production match achieved using thissimulator allowed us to re-calibrate the layer information fromthe original log interpretations, resulting in highly accurateproduction forecasts. A brief discussion of the simulator isalso included in the paper. The trend toward larger treatments and coarser proppanthas (1) produced higher-conductivity fractures and (2)significantly improved production from fields in westernSiberia. At the same time, the trend has created longereffective fractures and in some instances increased access towater through inter-well communication. This developmenthas underlined the importance of understanding reservoirsaturation and waterflood patterns, so that full advantage canbe taken of the increased conductivity through gain in oilproductivity.These techniques of reservoir simulation and studyinginjector proximity were then employed in the field forcandidate selection. The result has allowed fracturing to beperformed in this field with greater confidence inpredictability of post-fracture productivity. This paper presentsthe field study illustrating the developed methodology.