Research On Numerical Simulation Of Low Permeability Reservoir

With the great development of the oil industry and the sharp increase in oil consumption, there is no doubt that the exploitation of low permeability reservoir will be one of the focal points in the near future. Reservoir numerical simulation could provide theoretic support and related methods for the scientific and high efficient exploitation of such kinds of reservoirs. However, the traditional simulation methods did not account for the nonlinear characteristics of the flow in the low permeability reservoirs, which would not be correct for the description of these reservoirs'development. Therefore, it becomes urgent to study the development law of the low permeability reservoirs.Based on an intense literature review of flow in low permeability reservoirs and numerical simulation technology, taking starting pressure gradient and stress sensitivity into consideration, we have developed reasonable mathematical models which account for the fluid characteristics of the low permeability reservoirs, which includes a two-dimensional mathematical model of oil-water two-phase and a three-phase three-dimensional one. In addition, the mathematical models are solved with fully implicit solution and further realized by C++ programming. Using this calculator program, the affecting factors of the deliverability and the flow characteristics in the low permeability reservoirs are studied. The results indicate that there are strong nonlinear characteristics for the low permeability reservoirs. Moreover, starting pressure gradient and stress sensitivity have obvious effect on the deliverability of low permeability reservoirs. With an increase of the starting pressure gradient and a steady bottom hole flowing pressure, there will be a reduction in the pre-breakthrough oil production and the steady production after breakthrough as well. Meanwhile, the breakthrough time will be postponed. During the production procedure, the permeability would decrease with the increase of pressure due to stress sensitivity. Therefore, to maintain a constant injection and production, a greater injecting pressure is desired, and a greater pressure difference is needed for the production wells. During the water injection procedure of low permeability reservoirs, the deliverability of different phases will increase with the increase of the injection-production pressure difference and decrease with the increase of starting pressure gradient, medium deformation coefficient and the injector-producer distance. The influence of capillary pressure on the deliverability is insignificant, but the breakthrough time will move forward. The oil-water viscosity difference has significant influence on the breakthrough time. The greater the oil-water viscosity difference is, the earlier the breakthrough time comes, and the less is the oil recovered with the same water cut.