Research On Under-injection Factors Of Water Injection Wells In Geng83 District Of Jiyuan Oilfield

The prime block of the Jiyuan Oilfield,Geng83,is an ultra-low permeability reservoir.After long-term water injection exploitation,the most serious issue of the water injection well has been revealed as the lack of water injection.Up to the year-end of 2018,the issue such as extremely high injection pressure and rough in injecting water into the stratum of the research region had exposeed,resulting in an increase number of under-injector wells in research region,which immensely limited the potential of Geng83.The thesis contents base on the sedimentology,petrology and reservoir protection subject knowledge as the academic guideline.The research ranges from macroscopic to microcosmic,from the geological traits to the microscopic pore structure of the reservoir.To acquaint with the properties of reservoir lithology and pores.Research were investigated by electron microscopy,casting thin section,X-ray diffraction analysis,and other experiments or technical means.Water quality compatibility experiment and reservoir sensitivity experiments have been carried out.And through the simulated water flooding experiment and CT test.Combined the unsatisfactory circumstance of the current low injection well,made a systemic analyse towards the impact factors of Geng 83 underinjection izzue.Based on the above experiments and research result,The fundamental reasons which lead to the target issue has been demonstrated as geological factors and follows.The reservoir in the research region is compact and the reservoir properties are inferior.It belongs to the ultra-low porosity and ultra-low permeability reservoir.The content of cement is high,containing a large amount of sensitive minerals.The vertical and conplane heterogeneity is greatly different.The main types of pore throats are fine poret and small pore thin throat.The compatibility between the injected water and the formation water is poor.the results show that the ion composition and salinity of produced water vary greatly and the water type is different,and scale blockage will occur in the process of water injection.Through the analysis of the sensitivity,velocity sensitivity of the reservoir is moderately strong,moderately weak water sensitivity,The acid sensitivity damage is weak.Trough water flooding experiment and CT test shows that clay expansion and migration damage reservoir permeability and pore structure.The system pressure is low and the oil pressure is high,making the lack of injection for the injection well of Area Geng83.it is concluded that geological factors are the fundamental factors that affect Area Geng83 lacks of water injection.Sensitivity damage is the direct factor,The water quality and scale formation of injected water are the fluid factors.Wettability transformation are the development factors affecting waterflood development.