Study On The Mechanism Of Core Imbibition And The Method Of Huff And Puff Of Water Injection In Tight Oil Reservoirs

In recent years,the development of tight oil and gas has become an important field of energy succession in China.Tight oil development is difficult because of the main problems of poor reservoir physical properties and low seepage capacity.After horizontal well volume fracturing technology,the initial high productivity was obtained,but then the problems of rapid formation pressure drop and rapid decline of single well production and other problems appeared.Huff and puff of water injection technology can not only supplement formation energy,but also make full use of imbibition to achieve oil-water replacement.However,at present,the main control factors of huff and puff of water injection technology are not clear,the efficiency of oil and water replacement is low,and the effect of multiple rounds of huff and puff of water injection is gradually becoming worse.Therefore,it is necessary to carry out research to improve the efficiency of oil-water replacement,to achieve output replacement and benefit development.This paper uses the tight oil data from Tuha Oilfield to carry out core analysis and imbibition experiments to study the mechanism and main controlling factors of tight oil core imbibition.Screen and evaluate surfactants to study the effect of surfactants on improving core imbibition.Carry out core huff and puff of water injection experiment and single well huff and puff of water injection numerical simulation.Study the main control factors of huff and puff of water injection,optimize the design of huff and puff of water injection parameters,and form the technical method of tight oil huff and puff of water injection.First,the core imbibition experiment and nuclear magnetic resonance technology show that the influence of various factors on the imbibition recovery degree is from large to small in order of permeability,porosity,saturated oil viscosity,initial oil saturation,Specific surface area and temperature.The effective imbibition mainly occurs in the surface layer,and the depth of imbibition under formation conditions is about 0.41 cm.At the same time,the theory of rapid surface imbibition and the imbibition process are described.Secondly,in order to improve the imbibition efficiency of tight oil cores,suitable surfactants are screened.To study the effect of Tween 80,Tween 20 and WLW(Sodium secondary alkyl sulfonate +coconut diethanol amide)surfactants solution on improving the imbibition efficiency of dense oil.The results show that: reducing interfacial tension,improving wettability,and lowering the adhesion work reduction factor can reduce the flow resistance,increase the imbibition power or increase the difference between the imbibition power and the resistance,improve the oil-water replacement efficiency,and achieve the purpose of surfactants to improve the efficiency of imbibition.Finally,through the huff and puff of water injection experiment of the core,the effects of the opportunity of huff and puff of water injection,the development of cracks,the round of huff and puff of water injection,the addition of surfactant and other factors on the degree of production of huff and puff of water injection were analyzed.The geological model of single well huff and puff of water injection was established,and the numerical simulation of single well huff and puff of water injection was carried out.The influencing factors of single well huff and puff of water injection are clarified in order of rounds of huff and puff of water injection,Volume of water injected,soak time and injection speed.Optimize the parameters of the fourth round of huff and puff of water injection in a single well,and study the effect of adding surfactant on the single well huff and puff of water injection.This study provides technical support for the development of huff and puff of water injection and stimulation of similar tight reservoirs.