Vaporization Development By Injecting Natural Gas In Unconventional Low Permeability Sandstone Reservoir

The unconventional low-permeability sandstone reservoir has the characteristics of low porosity,low permeability,low pressure,low production and low recovery rate,which makes it difficult to exploit this kind of reservoir efficiently by traditional production methods.In view of this problem,this paper proposes to continuously inject natural gas into the low-permeability reservoir,maintain the formation pressure,and continuously extract and vaporize light and medium components from the reservoir,So as to achieve the purpose of enhancing oil recovery by vaporization.In this paper,reservoir numerical simulation technology is used,and the phase behavior of crude oil physical parameters of the target reservoir is fitted by Winprop module of CMG software.The gas-liquid phase equilibrium and physical parameters of the original fluid and the system mixed with natural gas in different proportions are calculated,which verifies the possibility of enhancing oil recovery by natural gas injection in the target reservoir.The GEM module of CMG software is used for dynamic prediction of several different development modes of the target reservoir.The development processes and effects of square anti nine-point pattern natural depletion production,water injection production and natural gas injection vaporization production are analyzed and compared.The well spacing,bottom hole flow pressure and gas injection volume are optimized.The development process of natural gas injection vaporization production of the target reservoir is analyzed,the influence of well pattern change on development effect is studied.The conclusions are as follows:(1)the recovery of natural depletion mining is low,and the highest recovery rate is about 12%;The recovery of waterflooding can reach about 28%,but the water cut of production wells will be too high soon.(2)When the square reverse nine point pattern is used to inject natural gas,the bottom hole flowing pressure of production well is kept unchanged,and the increase of gas injection rate is helpful to enhance the recovery;At the same gas injection rate,a higher bottom hole flowing pressure of production well is maintained,and the recovery is higher.(3)When injecting gas,adding appropriate amount of dissolved gas can reduce the viscosity of crude oil and improve oil recovery.(4)After gas injection,the distribution of components in the reservoir,the change of oil and gas saturation in the reservoir and the change of component composition of products from production wells directly show the process of gas injection and vaporization in unconventional low permeability sandstone reservoir.(5)The comparison of component content,oil and gas saturation and product composition change data in the grid of corner well and side well shows that the later the gas breakthrough in the production well,the higher the vaporization effect and the higher the oil recovery.(6)When the well pattern is adjusted,when the gas breakthrough at the side well,the side well is closed immediately,and the development effect is the best.The final recovery can reach 48.64%,which is 21.13 percentage points higher than that before the adjustment.(7)When the working system of wells remains unchanged,the development effect of natural gas injection vaporization with 353.m well spacing and five-point well pattern is better,and the recovery can reach 50.79%.(8)The recovery of unconventional low permeability sandstone reservoir can be greatly improved by vaporization development with natural gas injection.