Study On Control Method Of Deep Profile Control System By Single Slug

At present,most of the onshore oilfields in our country have entered the middle and late stage of development.In the process of water injection development,because of formation heterogeneity and long-term erosion of injected water,injected water mainly rushes along the formation's high permeability channel,which leads to the ineffective circulation of injected water.Therefore,profile control and water shutoff are needed.At the same time,with oil and gas development going deep,more and more newly developed oilfields are facing the development environment of high temperature,high salinity or low permeability,which puts forward higher requirements for profile control and water shutoff chemicals.At present,the research of profile control agent is mostly focused on polymer gel and microsphere,and there are still some problems in temperature resistance,salt resistance and injectability.In this paper,the precipitation profile control agent with the characteristics of high temperature and salt resistance and good injection property is studied.In this paper,three kinds of precipitation profile control systems are put forward around high calcium formation water.The basic properties of profile control system,the influencing factors of profile control system and performance control methods are studied.The plugging performance of profile control agent is evaluated by physical model experiment,and the plugging mechanism is revealed.The main research contents and conclusions are as follows:(1)inorganic precipitation profile control system by single slugThe feasibility of single-liquid injection of sodium carbonate/mineralized water precipitation profile control system was explored by temporarily suppressing precipitation formation with precipitation inhibitor.Experiments show that in most cases,the initial dilution ratio of precipitation is linearly related to the concentration of the precipitation inhibitor;the amount of precipitation increases first increases and then decreases with the increase of the dilution ratio;the initial dilution ratio of precipitation decreases with the increase of temperature or salinity,and the amount of precipitation increases slightly.The system has good injection performance.It can inject into medium and low permeability cores without end blockage.The blockage rate can reach 70%and has scouring resistance.(2)emulsion precipitation profile control systemUsing oxalate ester as Ca²⁺precipitant,the oxalate ester was dissolved in kerosene.The oil in water emulsion type precipitation profile control system was made with high Ca²⁺mineralized water.The system can obtain different precipitation amount by adjusting the concentration of oxalate ester and Ca²⁺;long precipitation time can be obtained at low temperature;with the increase of salinity,the precipitation time is slightly prolonged and the precipitation amount decreases.The system has good plugging effect for high permeability formation,the plugging rate can reach 98%and has good scouring resistance.(3)aluminium chloride/hexamethylene tetramine profile control systemThe aluminium chloride/hexamethylene tetramine profile control system of low temperature with adjustable product morphology was obtained by using hexamethylene tetramine as p H regulator.For a certain concentration of aluminum chloride,high concentration of hexamethylene tetramine can be used to produce gels.Precipitation can be obtained by using low concentration of hexamethylene tetramine and sodium sulfate.With the temperature increased,the gel time of the gel system shortened,and the salinity had little effect on the system.The injection property of the system is between the inorganic precipitation profile control system by single slug and the emulsion precipitation profile control system.The plugging rate of gel system can reach more than 95%,and the plugging rate of the precipitation system can reach 66%.For polymer flooding formation,the plugging rate of the precipitation system can reach more than 84%,and it has scouring resistance.