Research On Fine Reservoir Description And Numerical Simulation Of Steam-injection Development After Water-flooding In Heavy Oil Reservoir

For heavy oil reservoirs of steam-injection development after water -flooding, after different exploitation stages of cold production, water-flooding, steam buff and puff, steam flooding and the frequent adjustment in above-mentioned production method, many effects such as distillation, decline in oil viscosity, water gravity segregation, steam overlap, thermal expansion effect of formation fluid and rock, changes in rock wettability lead to variations in formation characteristics and fluid flow mechanism in porous media, which makes research on fine reservoir description and numerical simulation of steam-injection development after water-flooding extremely complicated in heavy oil reservoirs.During the water flooding stage, the injected water may not match with the original formation water; and during the stage of steam injection, the salinity of injected steam is far more lower than that of the formation aquifer, which induces formation clay expanding, and especially, when the salinity of injected fluid is lower than critical salinity of clay, clay expands greatly. Thus, formation permeability will decrease dramatically. When steam is injected with a high velocity, clay particles will migrate and block the pore throat, which can also decrease the formation permeability. Furthermore, in the thermal process of heavy oil reservoir, the formation condition change will result in asphalt depositing and rock wettability variation, which will cause the formation porosity and permeability to decrease severely, especially in the area around the well-bore. The formation damage will greatly reduce oil production rate.Traditional reservoir description software and numerical model in heavy oil reservoir simulator haven't taken into account of the changes in formation porosity and permeability and neglected the influence of formation damage to heavy oil reservoir, thus it become unreliable to design and adjust development plan and forecast production performance.In this article, in view of characteristics of easy-damaging in heavy oil reservoir of steam-injection development after water-flooding and based on the existing major problems in Kexia Group Liudong Section heavy oil reservoir, research on formation damage, fine reservoir description and numerical simulation have been conducted. Our in-house 3-D, 3-phase, compositional thermal simulator, named NUMSIP, has been reworked and further developed. Having taken formation damage into consideration, research on history matching and remaining oil distribution of the reservoir have been done and compared the production performance with formation damage and without formation damage.Main research findings:Under the control of depositional phases, by combining with decided modeling method and stochastic modeling method, fine reservoir description was conducted in Kexia Group heavy oil reservoir and a reliable and accurate 3-D geological model was then built up;The formation damage mechanism and its evaluation for Kexia Group Liudong Section heavy oil reservoir of steam-injection development after water-flooding is analyzed and studied;Our in-house 3-D, 3-phase, compositional thermal simulator, named NUMSIP, has been reworked and further developed and formation damage has been taken into account in the model;Having taken formation damage into consideration, research on history matching and remaining oil distribution of the reservoir have been done and compared the production performance with formation damage and without formation damage.