Comprehensive Evaluation Of Compatibility Water Injection In G Oilfield

In recent years,with the intensification of oil and gas exploration in China,the proven reserves of low permeability oil and gas resources are increasing,and the development of low permeability reservoirs has become the focus of domestic attention.Waterflood development is the most commonly used development method for low permeability reservoirs,and the compatibility of injection water and reservoir seriously affects the waterflood development effect.Therefore,improving the compatibility of injected water and reservoir is of great significance for the realization of high-efficiency water injection in low-permeability reservoirs.At present,the waterflood development of low-permeability and high-temperature reservoirs in G oilfield mainly uses sewage reinjection,and the compatibility of injected water and reservoir is generally poor,which leads to problems such as high injection pressure,low water absorption and short water injection period.The water quality standard of the petroleum industry has a wide range of permeability,which results in poor compatibility between injected water and low permeability reservoirs.The standard cannot be directly used.In response to the above problems,this paper carried out the following research work:(1)The basic physical properties,pore throat structure and distribution,sensitive clay minerals,formation fluids,reservoir temperature and pressure system of G oilfield reservoir are analyzed.The radius range of main throat and potential damage factors of reservoir are defined,which provides scientific basis for analysis of waterflood damage mechanism and experimental design of compatible waterflood quality index.(2)The current situation of injected water quality control in G oilfield is deeply analyzed,and the existing problems and reservoir damage mechanism of injected water in G oilfield are clarified.Core damage evaluation experiments are carried out in laboratory,and combined with the impedance of water injection wells on location,the damage degree and types of reservoirs caused by injected water are defined.(3)Aiming at the problems of strong water sensitivity of high temperature reservoir in G oilfield,serious scaling of injected water and incompatibility with formation water,a variety of anti-swelling agents and scale inhibitors were selected,and their performance evaluation was carried out respectively.The anti-swelling agents(No.2,No.5)and scale inhibitors(MT-1)with strong temperature resistance and excellent comprehensive performances were selected,and the optimum addition concentration was determined.(4)According to the statistical analysis results of low permeability reservoir characteristics and formation coefficients of water injection wells in G oilfield,the permeability range of water injection wells and water injection horizons which need to be protected in the process of water injection development in G oilfield is defined(1<K<10mD);a comprehensive and systematic compatibility experiment of water quality index of injection water is carried out,with emphasis on the analysis of suspended particle size and content and emulsified oil content in injection water.The matching relationship between suspended particle size and pore throat diameter was determined,and the high and low limit of compatible injection water quality index was recommended.Finally,a feasible compatible water injection quality system standard for G oilfield low permeability high temperature reservoir is proposed,which provides experimental basis and technical guidance for the realization of high efficiency water injection development,and also provides reference for water flooding development of the same type of reservoir.