Aternating Oil Drive Technology Of Oil And Water Wells For Lowpermeability Oilfield

Nuclear-magnetic-resonance tests and pore-structure analysis show the differences between low-permeable and high-permeable cores . For low-permeable cores , though no much difference between big and small pores , the neck is very narrow . During the process of forward displacement , oil flow is vulnerable to be interrupted by the necks , remaining a lot of oil in pores . When backward displacing , due to the Jamin effect , the remaining oil in pores are hard to connect together and forming a running oil flow .The extracted oil is only the ones from a few big pores in the production end where has a high oil saturation . For high-permeable cores , there has much difference between big and small pores and the necks are broad . When forward driving , due to the trapping effect of capillary , a host of oil residue stay in big pores and a part of them start to flow outside when turn to backward driving . So backward displacing in high-permeable cores could increase oil recovery in a high degree .When there are faults at 30m,60m , 110m and 160m away from borderline wells , the numerical simulation of alteration show that a over-50m fault slip condition could get more oil production increment . For a well group with isolate sands , the numerical simulation indicates economic benefits of altering injection well into production well could only be realized when the sand thickness is over 3.5m .For a inverted nine-spot well groups in which the faults are 60m , 110m and 160m away from the injection well respectively , the alteration time and period and other dynamic indexes are numerically simulated . Under a 23MPa fixed injection pressure , 2.5 years , 3.5 years and 5.0 years after the initial injection , the average formation pressure of injection wells is about 20.0MPa . The pressure difference between injection wells and production wells is approximate to zero and then the average formation pressure keeps stable . Obviously , 2.5 years , 3.5 years and 5.0 years after the initial injection are the reasonable alteration time . After 3.0 years , 4.0 years and 5.0 years producing , the average formation pressure of production wells that altered from injection wells reaches to about 8.5MPa and then remaining at this level by the energy supplement from inner-side injection well . So the proper alteration period is 3.0 years , 4.0 years and 5.0 years . A injection well which has isolate sands should be altered into production well 3-6 years after the initial injection and the alteration period is 4-5 years . However , all kind of injection wells should not be altered more than two times .According to the geological characteristics of class No.1 , No.2 and No.3 blocks of Chaoyanggou Oilfiled. And the ppaper presents the practical technical limitations of key parameters indexes of altering injection wells into production wells in low-permeable reservoirs . It could increase oilfield development degree , exploring more residual oil and realizing sustainable oilfield development .