Experimental studies on production performance of oil reservoirs with bottom water

Abstract

Water coning is a major problem in oil reservoirs with bottom water. It reduces the oil production and overall oil recovery. Excessive water production causes corrosion problems in production facilities and increases the cost of water disposal. This may cause the early shutdown of oil wells. In this study, an experimental apparatus has been designed and developed to physically model an oil reservoir with bottom water. The reservoir model was transparent and the change in water coning could be visualized. Many water-flooding tests were conducted at different pressures and oil viscosities ranging from 22 to 260 mPa s. The effects of production pressures and oil viscosity on oil production were investigated. The results indicated that for a medium oil viscosity of 74 mPa s, the optimal production pressure was about 0.054 bar. For minimum and maximum oil viscosity (22 mPa s and 260 mPa s), the smaller the production pressure, the larger the water breakthrough time and oil recovery. Five types of flooding characteristic curves were used to characterize the water-cut variation, and their applicability were compared and analyzed. The water drive curves were fitted using the water-cut models and the oil “reserves” (originally placed in the reservoir model) were predicted using the mathematical models with the experimental data. The results indicated that the Maksimov model of water-drive characteristic curve is more suitable to match the water production performance. Most interestingly, when applying the most suitable model Maksimov water-drive characteristic curve to predict oil reserves, the cases with optimal production pressures have a greater accuracy.