Study On Gas - Water Infiltration Of KS Ultrahigh Pressure Gas Reservoir

Gas and water relative permeability are important parameter for the establishment of gas field development, dynamic prediction and reservoir simulation. KS dry gas reservoir is characterized as low porosity and low permeability. The reservoir has large inclination angle and matured fractures, whose depth is about7000m, with the formation temperature of160degrees Celsius and pressure of116MPa. The test method of gas water relative permeability is usually based on the industry standard SY/T5345-2007"test method for two phase relative permeability in rock", applied nitrogen (or compressed air) and formation water (or standard salted water) by the method of steady or unsteady drive. As the relative permeability measurement under formation temperature and pressure has never been reported, the actual flow may show some difference with the previously tested results, which brings some difficulty to study on this project.Based on understanding the literature researches in this field in and abroad, our research group invented method for testing the gas and water relative permeability under high temperature and pressure. The test method contributed to an invention patent. We carried out laboratory research on cores from KS gas reservoirs to measure the relative permeability under160degrees Celsius and pressure of116MPa. Five matrix cores are utilized to test three groups of gas drive water relative permeability and water drive gas relative permeability respectively, and nine fractured cores (CT scan) are applied to test nine groups of water drive gas relative permeability.The results show that:(1) For the matrix cores, the relative permeability curves under high temperature-pressure have lower bounded water saturation and wider area for two-phase flow than the atmospheric conditions;(2) Compared to the curves under atmospheric conditions, the water drive gas relative permeability curves under reservoir conditions show significant difference:the curves have higher residual gas saturation, the two-phase flow area is narrower and the water relative permeability is slightly higher;(3) The relative permeability curves under high temperature-pressure have no clear regulation due to the complex fracture exists the same as they at room conditions;(4) The relative permeability curve of fractured core at high temperature-pressure shows narrower two-phase flow area, low water relative permeability under irreducible gas saturation and low water drive efficiency.