Research On Drainage/Imbibition Capillary Pressure Curves Measurement And Application

The drainage capillary pressure controls the oil-water distribution in the process of hydrocarbon accumulation in low permeability reservoirs,and the imbibition capillary pressure affects the flow and distribution of oil and water in the process of water flooding development(water-wet reservoir,for example).The imbibition capillary pressure curve in the transition zone is related to the initial liquid saturation,and the capillary pressure curves are different at different heights.However,the traditional calculation only uses the drainage capillary pressure curve at the initial saturation,which results in a large deviation between the numerical simulation and the actual performance in low-permeability reservoirs.Therefore,the correct use of capillary force curve is of great importance for the development of low permeability oil and gas fields.Based on porous plate method,a method for simultaneously testing of oil-water drainage and imbibition capillary pressure curves is proposed in this paper.The drainage and imbibition capillary pressure curves are tested of different permeability cores with different salinity fluids.And the scanning capillary pressure curves which means initial water saturation is greater than irreducible water saturation are also tested.Also,mercury injection capillary pressure curves of the same cores are measured and converted to compare with the oil-water capillary pressure curves.Based on experimental data,this paper compared some capillary pressure-saturation models,and presented an improved method describing and predicting the oil-water capillary pressure curve.Finally,the influence of different capillary pressure curves on the development performance of low permeability reservoir transition zone is studied by numerical simulation.The results show that,the capillary pressure curve of mercury injection capillary pressure conversion is quite different from the oil-water curve and cannot be directly used in reservoir engineering calculation.Fluid salinity has little effect on oil-water capillary pressure curve,while permeability has a great influence on capillary pressure curve.With the decrease of permeability,the irreducible water saturation increases and the flat section narrows.When the initial water saturation is greater than the irreducible water saturation,the imbibition curve moves to the right,and the movable water area narrows.The new model improved by capillary pressure curve in homogeneous reservoir can fit well and predict effectively with the capillary pressure curve of low permeability sandstone.Different capillary force curves have great influence on oil-water distribution and development performance in reservoir transition zone.In reservoir numerical simulation,it is important to test and use capillary pressure curves accurately.