The Mechanism And Characteristic Study Of The Gas Miscible Flooding In Donghetang Oil Reservoir

The development method of hydrocarbon gas flooding was applied in Donghetang reservoir of Tarim Oilfield in 2014,and it works well.What'more,the corporation prepared to use this method in the greater scope.The research object of this paper is Donghetang reservoir which developed through gas injection.The paper was completed under the project of "the evaluation of gas injection development and the optimization of injection production parameters" in order to evaluate the development effect of miscible hydrocarbon gas flooding in the oil area.Based on the experimental and field data,the numerical model of the reservoir is established,and the remaining oil distribution is analyzed.This paper analysis the miscible gas flooding mechanism through the P-X phase diagram,pseudoternary phase diagram and the slime tube test characteristic curve,and establishs a new model which can predict gas flooding minimum miscible pressure.Through slime tube and long core experiment numerical model,analyzes the influence of various parameters on mixed volume,what's more the empirical formula was established to predict miscibility zone size,and tested using the actual reservoir model.Based on the accurate calculation of miscibility zone volume,a new material balance equation is established.Based on the above research contents and results,the following conclusions are obtained:(1)There are some defects when the traditional material balance equation apply in miscible flooding reservoirs.This paper establishes the material balance equation of miscible displacement considering interphase mass transfer.(2)The the miscibility zone siz can be predicted using the prediction formula,and can provide reference for the dynamic analysis of the field.(3)The volume of injection gas,formation pressure and permeability will affect the miscibility zone size.With the increase of injection gas volume,pressure and permeability,the longer the miscibility zone size,and there is a linear relationship.But,when the permeability is greater than a certain value the change is very small.(4)A11 of the existing calculating formula of gas flooding minimum miscible pressure have limited precision,the new model established by the dry-gas drive sample data in this paper improves the prediction accuracy.(5)After the injection of gas,intermediate hydrocarbons in crude oils are extracted to the injected gas.the density and viscosity of injected gas increases,but the viscosity of crude oil reduces.In summary,it belongs to vaporizing miscible mechanism.(6)Through the Donghetang reservoir numerical model,doing the dynamic analysis of gas injection region and getting the distribution rules of remaining oil.