Laboratory Study On Oil Displacement And Storage Effect Of Fire Flooding Tail Gas Reinjection H Reservoir

Breakthrough progress has been made in the steam development and conversion of the heavy oil main development zone in Xinjiang.The fire drive production has been improved for nearly 6 years,the recovery degree has increased by 19.4%,and the remaining oil recovery of the burned volume has been 69.9%,It is proved that the feasibility of turning fire flooding in the later stage of steam injection in glutenite reservoirs,but the tail gas output generated during the fire flooding process is as high as 2.1×106m3,Tail gas contains harmful gases such as CO2 and H2S,Therefore,the flue gas is injected back into the oil layer,which can not only store harmful gases,but also increase crude oil production.The promotion and application of fire drive and gas drive technology has important practical significance.In this paper,on the basis of fully investigating the enhanced oil recovery and storage effect of the tail gas flooding,combined with the actual production data of oilfield,used a combination of laboratory physical simulation experiments and numerical simulation methods,to carry out the analysis and argumentation.Firstly,the effects of different injection gases on oil recovery were studied by long core experiments.Then,the embedding effect of flue gas under different gas injection modes was calculated.Finally,numerical simulation was used to reverse the gas-oil phase permeability and experimental measurements under reservoir conditions.The gas-oil phase contrast is obtained,and the actual flue gas(including H2S)storage and oil displacement effect are predicted.The following conclusions and understandings have been made:1)The long core displacement experiment shows that gas drive can substantially enhance oil recovery.After water flooding,the recovery degree was increased by 23.54%,15.37%and 10.81%,respectively,by CO2 flooding,flue gas flooding and nitrogen flooding,respectively.The recovery degree of CO2-flue gas combined flooding was 6.33%higher than using only flue gas flooding.2)The tail gas storage experiment shows that before the gas breakthrough,the injected gas is completely stored in the core;After the gas breaks through,part of the gas phase is driven out by water during the alternate flooding,resulting the stored ratio is much lower than that of continuous flooding;mainly CO2 and N2,gas-water alternative is beneficial to the CO2 storage.3)The numerical simulation is used to fit the relative permeability curve under reservoir conditions.It shows that the gas-oil phase mass transfer under reservoir conditions leads to an increase in gaseous viscosity,a decrease in oil phase viscosity,a decrease in gas phase relative percolation ability,and an increase in oil phase relative percolation.Moreover,the span in common permeable region in oil and gas phases is wider,the residual oil saturation is low,and the oil displacement efficiency is higher.4)In the numerical simulation study of actual flue gas,it is found that the content of H2S in the flue gas has little effect on PVT properties of crude-oil and oil displacement efficiency.When gas breakthrough occurs the continuous gas flooding and water-alternating gas,the H2S content in the produced gas is 70 ppm and 25 ppm,respectively,which is much lower than the injected H2S content of 250 ppm.Therefore,the water alternating gas displacement is more conducive to the storage of H2S.