Mechanism Study On The Applicability Of Air Injection On Thin Oil Reservoirs

After a long period of waterflood developmen,most oilfields in our country represent high water cut,pressure drop and production reduction.Air injection provides a new way to enhance oil recovery.Many researches have been done on the applicability of air injection.Some of the screening conditions have been proposed.However,due to the different basis of screening,no uniform standard has been formed so far.Therefore,the applicability of air injection reservoirs needs further exploration and research.In this paper,the oxidation limit of crude oil is studied.The correlation between experimental exhaust gas and oxidation state and oxidation parameters is discussed,and the criterion of oxidation state is established.Second,according to the previous screening method of fire flooding reservoir.Based on the statistical difference confidence method,the influence factors on the field air injection test are analyzed.The grey correlation method is used to evaluate the impact of the factors,and the interval estimation of the influencing factors is made.Interval estimation is also made for the range of factors.Based on a multivariate linear regression model,an equation is established to distinguish the success or failure equation of an air injection project.Finally,by establishing the numerical simulation model of air injection,the main displacement mechanism of air injection is studied.High temperature and low temperature oxidation process is simulated to verify the reliability of the oxidation criterion.And the applicability of air injection is analyzed.The results show that there is a certain correlation between exhaust gas and oxidation state.The correlation between the exhaust gas and the oxidation parameters is varied.A reference table for oxidation state is purposed.Six factors affecting air injection are obtained: oil layer thickness,reservoir temperature,reservoir pressure,permeability,porosity and viscosity of crude oil.The Z function is purposed to evaluating the success of air injection on thin oil reservoirs.Numerical analysis shows that the main mechanism of air injection on thin oil reservoir is flue gas drive.The results of high temperature and low temperature oxidation conform to the reference table of oxidation state.This research of applicability of air injection has a practical meaning for guiding oil field development.