Comprehensive Evaluation of Influence Factors upon Productivity for Complicated Faulted-block Reservoirs

Abstract

Currently there are many complicated faulted-reservoirs discovered in Niger. For this kind of reservoir, comprehensive evaluation of oil rate or productivity is essential, because it is crucial for the construction and investment of the oilfield. Oil rate variance is closely related to tectonic characteristics, natural energy, reservoir physical property or quality and so on. The research results indicated that aquifer energy of monocline is stronger than that of horst and faulted block. Consequently production plateau and recovery factor of monocline is also higher than horst and faulted block. With the decrease of oil viscosity, initial production, production plateau and recovery factor is relatively higher. With the increase of permeability, initial production, production plateau and recovery factor is relatively higher. Single well initial production is sensitive to drawdown pressure. While the drawdown pressure is increased to some extent, growing rate becomes smaller. For the natural energy adopted stratified reservoir with strong heterogeneity, one set well pattern and the type of upward layer by layer is more suitable. Reasonable offtake rate is around 2% and could be modified according to natural energy. If the natural energy is sufficient, offtake rate could float upward properly and vice versa. In general case, water injection is not suitable in consideration of desert conditions and large investment. Only for the blocks with insufficient natural energy and large OOIP, water injection could be taken into account.