The Study Of Flowing Law Of Oil And Water In Low-permeability Reservoir

The pore and throat of low permeable reservoir are very small, and the fluids flowing in it do not abide Darcy's law, and there is threshold pressure when fluids begin to flow. Now the studies about threshold pressure are mainly in theory but little in laboratory. On the base of the study of predecessor, this paper do a great deal of flowing experiments and analysis by using the natural low permeability rock of Shengli oil field, and makeing more studies in the flowing law of the low permeability reservoir.On the base of the research of single flowing law and the reason of the threshold pressure in the low permeability reservoir,this paper design the equipment to study single flowing law and the threshold pressure. By regression the experimental data, the relationships between the threshold pressures and the ratio of gas permeability of rock to the viscosity of fluids are obtained. The parameters modifying the shape of velocity-pressure gradient are also obtained. Then the empirical figure for determining the min- and max-threshold pressures are built. the feature of the threshold pressures and the depicting way of single flowing are also obtained.On the base of the research of two-phase flowing threshold pressure in the low permeability reservoir, this paper design the equipment to study two-phase flowing law and the threshold pressure, and study the feature and the influential factor of the two-phase flowing threshold pressure, build the functional relationship of the two-phase flowing threshold pressure vs. permeability and Sw , and build the empirical method to depict the rule of two-phase flowing. By these results the description of the fluids flowing in low- permeability reservoir are quantitatively and more accurately.The curve of velocity-pressure gradient is not straight line or passes through origin. So the formula used to calculate relative permeability by non-steady state method based on the Dacy's low is not suitable. The stead state method of determining the relative permeability curve(RPC) is improved based on the study of the characteristic of low permeable reservoir rock (LPRR). The unitary or standardization method is put forward to average and calculate RPC.The study shows that the threshold pressures and the flowing law are in connection with the rock nature and permeability and fluid nature, the two-phase threshold pressure is in connection with rock permeability and the Sw, the relative permeability curve parameters have good relationship with the rock permeability and the fluid velocity. This paper build a series of forecasting formulas for quantitatively depicting the flowing law of the low permeability reservoir.