Experimental Study On CO₂ Huff And Puff Of Tight Glutenite Reservoirs

With the further improvement of global conventional oil reservoir exploration and development,the reserves of conventional oil reservoirs are constantly declining and the difficulty of development is increasing,and tight oil reservoirs have gradually become the focus of global attention.China,s tight oil resources are widely distributed and have broad prospects for development.According to the evaluation of oil and gas resources in recent years,tight oil resources account for 40%of the domestic recoverable oil resources.The natural energy of M tight glutenite reservoir in Xinjiang is low,the formation pressure and production are rapidly decreasing,and it is difficult to replenish formation energy,the recovery rate is low at the present stage.Combined with geological and reservoir characteristics,it is considered that CO2 huff and puff has certain potential for the development of this reservoir.Through the relevant experimental research on COZ huff and puff of M tight glutenite reservoir,this paper clarifies the potential of COZ huff and puff to replenish energy,which can provide certain theoretical reference for the development of CO2 huff and puff of this reservoir.By studying the basic characteristics of core,the results show that the rock is compact as a whole,and clay minerals such as kaolinite are distributed on the surface of particles and in the interior of intergranular pore,The rock mineral composition is mainly quartz,feldspar and clay minerals;the analysis of formation water ion composition shows that the formation water is CaC12 type and the total salinity is high;through the study of CO2-fonmation water-rock interaction,the results show that with the increase of reaction time between rock and COZ and formation water,the content of K+ and Na+ in formation water increases obviously,and the dissolution of potash feldspar and other minerals occurs,and a small amount of dissolution pore appears,the migration and deposition of clay mineral particles will cause certain damage to the reservoir,and the hydrophilieity of the rock surface becomes stronger.By studying the characteristics of crude oil and the effects of CO2 on the high pressure physical properties of crude oil,the results show that the viscosity of crude oil decreases with the increase of temperature.The components with higher content in crude oil were concentrated in the range of C7?C15,and the content of light and heavy components was lower.With the increase of CO2 injection,the viscosity of crude oil decreases,the bubble point pressure,volume coefficient,expansion coefficient and dissolved gas-oil ratio increase.Physical simulation experiments of C02 huff and puff show that,within a reasonable range,increasing the amount of CO2 injection,huff and puff cycles and soaking time is conducive to improving the recovery of CO2 huff and puff;the greater the core permeability,the more favorable it is for oil production;the higher the original oil/gas ratio and volume coefficient,the smaller the density and viscosity,the higher the recovery of C02 huff and puff,and there is a reasonable time for CO2 huff and puff;the maximum increase of oil recovery by CO2 huff and puff is 24.16%.Nuclear magnetic resonance experiments of CO2 huff and puff shows that crude oil is mainly extracted from macroporous throat during depletion exploitation,while medium porous throat and small porous throat are also utilized to a certain extent during CO2 huff and puff,and with the increase of huff and puff cycles,the oil output of single cycle production decreases significantly.