Study On Mechanism Of Enhanced Oil Recovery By Partition Control Of Complex Fault Block Reservoirs

At present,with the development of the complex fault-block reservoirs,after many years of strong injection and production,more and more units have entered the high water cut period in the later stage of development.The imbalance between injection and production ratio has intensified,the development situation has gradually deteriorated.The geological characteristics of complex fault block reservoirs lead to the retention of a large amount of remaining oil in the development unit,and it is characterized by partition enrichment.It has important practical significance for the later development of the reservoir to clear that the mechanism of enhanced recovery of complex fault block reservoirs.Based on the distribution rule of remaining oil in complex fault block reservoirs,this study combines laboratory tests with numerical simulation techniques to carry out basic research work on water flooding rules and gas flooding rules of complex fault block reservoirs.In-depth understanding of the main control factors and mechanism of enhanced oil recovery,which could provide the basis for ethanced oil recovery in the late development of complex fault block reservoirs.By the research,this thesis has drawn the following conclusions:(1)The visual physical model of plane wave and profile high-pressure well group were designed and manufactured,which can be used for water flooding seepage law and high-pressure gas flooding seepage law in complex fault block reservoirs;The plan for plane water flooding and profile gas flooding were formulated.(2)The water flooding plane sweep experiment and mechanism simulation show that the injection-production well spacing in the injection-production control unit is the main factor affecting the recovery factor.In the experiment,the injection-production well spacing increases from 15cm to 20cm,and the recovery increased by 6.07%.The injection well type is the second,and the influence of the injection and production direction is the smallest.Among the mechanical parameters,the pressure gradient has the greatest influence on the recovery rate.The pressure gradient in the experiment increases from 0.3MPa/m to 1.2MPa/m,and the recovery increases by 6.72%.Followed by viscous forces,gravity differences,capillary force is weak.The main mechanism of water flooding plane and enhanced oil recovery are to expand the control unit of injection-production wells,increase the effective driving force and increase the volume sweep coefficient.(3)The high-pressure gas flooding experiment and mechanism simulation of the profile show that the gas injection in high-part is beneficial to the fornation of-secondary gas roof,while reducing the oil-water interface,and has the effect of controlling water and increasing oil,effectively improving the production status of-production wells.In the experiment,the ultimate recovery rate of bottom water-gas top drive can reach 34.78%,which increases 11.56%than bottom water flooding.Relying on extraction and gas-top assisted gravity displacement has a good effect on the high-grade attic oil and the remaining oil in the low-permeability zone,which can effectively improve the recovery factor of complex fault-block reservoirs.(4)The mechanism model conforming to the characteristics of complex fault block reservoirs is established.The simulation results show that the effect of corner well transfer is the best,the ultimate recovery can reach 59.75%,the development effect of horizontal wells is second,and the ultimate recovery can reach 59.02%.The variable flow line can not perform well in the later stage of development,and the final recovery factor was only 51.86%.Through the above research,the zonal seepage law and the mechanism of enhanced oil recovery in complex fault block reservoirs are clarified,which provides support for the enhanced oil recovery technology in the late development of complex fault block reservoirs.