| Xin Mu 69 block of Jilin oilfield was put into development in 1987 and expanded and adjusted in June 1997.The oil reservoir is lithologic structural reservoir,the nose structures for fault barrier,geological reserves of 3 million 20 thousand and 800 tons,oil-bearing area of 6.09 square kilometers.The main production layer is NO.4and 5 layer of Fuyu reservoir,and the original formation pressure is 8.25MPa,the average density of crude oil is 0.894,crude oil viscosity is about 45mPa.s,the average ground temperature is 60?,formation of the water is NaHC03,total salinity is about 8000mg/L,the pH value is 6?6.5.For the heterogeneity of interlayer and horizons,strong absorbing ability of high-permeability zone,forming a water channel and ineffective water cycle,while the low-permeability zone is not injected by water in water injection.(1)The article filtered the temperature resistance and salt tolerance polymer M69-3 after evaluating three kinds of polymer's thermal-endurance,salt-resistance,shear-resistance and gelling properties.(2)The influences of polymer type and its concentration,crosslinker type and its concentration,stabilizer,salinity,temperature and pH value upon the gelling properties were investigated.The appropriate composition of gel formula as followed:the M69-3 concentration was 0.3%,the mass ratio of polymer and crosslinker is 10:1.the crosslinker is chromium acetate.(3)The single rock flow experiment shows that the weak gel system has good injectivity in different rock cores,the resistance coefficient Fr range is 35?80,and the system has good plugging ability after gelling,and the plugging ratio ranges from 88%to 99.66%.With the increase of core permeability,the residual resistance coefficient Frr and the plugging ratio decrease.In the process of weak gel injection,the mobility ratio can be changed,and the oil displacement efficiency can be improved.After gelling,the high permeability channel can be blocked,the sweep coefficient of the injected water will be enlarged,and the oil displacement efficiency will increase by 15.65%.(4)The flow test of double parallel core shows that the greater the permeability difference between two cores,the greater the difference in water absorption.After the weak gel system was injected,the water absorption was obviously changed,and the gel system had better selective injectivity and improved profile properties.When the ratio of core permeability increases from 4.49 to 14.7,the improvement rate of profile increases from 76.4%to 98.77%.In the oil displacement test,when the permeability difference is 7.69,the remaining water of the low-permeability core is started by adjusting the water absorption profile of the gel system,and the efficiency of low permeability core flooding is higher than that of the hypertonic core,and the oil displacement efficiency increases by 39.26%.(5)The gel system has been applied to Mu 111-7 well group of Xin Mu 69 block,The results of field application show that this gel system can effectively block high permeability zone,divert the follow-injected water entering the low permeability zone.Consequently,swept volume of flood water can be improved greatly and higher oil production is achieved. |
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