| Chemical flooding is an important technique to enhance oil recovery. The technologies on enhancing oil recovery,such as alkaline flooding, surfactant solution flooding, polymer flooding, weak gel flooding, ASP flooding and chemical flooding,were investigated at the reservoir temperature of 113.8℃for Gao 30 in this paper. For the ultralow IFT technolog, four kinds of alkalines including NaOH, Na2SiO3, NaHCO3 and Na2CO3, and nine kinds of industrial Surfactants were used to lower interfacial tension to magnitude of 10-2 mN/m at which the residual oilcould be mobilized.The results display that The alkaline technolog could not be used to enhance oil recovery as the interfacial tension between alkaline solution and crude oil in the alkalinify of 0% to 0.30% is only lowed to 10-1 mN/m to 101 mN/m magnitude or It can't effectively improve the displacement efficiency. The 0.05% CDS-1 was favorablely screened out and the equilibrium interfacial tension, between surfactant solution and crude oil if the surfactant CDS-1 of 0.015%~0.30% are solved in Gao 30 ,could be lower to the 10-2mN / m ~ 10-3mN / m magnitude which greatly reduce the residual oil saturation.The synergistic interaction of CDS-1 and four kinds of polymers solution was observed in the visestigation.The CDS-1/HNT201-3 solution is viscous and the IFT is low.Unfortunately, the polymer technolog could not be used to enhance oil recovery as the decrease of viscosity from 72.37mPa?s to 8.2mPa?s or the percentage being 11.33 in 7 days and aging time which resulted from high reservoir temperature.The gel to control profile was screened out for fresh water performed in lab,but for brine produced.The gel system includes urotropine of 800 mg/L, resorcinol of 250 mg/L, oxalic acid of 350 mg/L and acid thickener B of 3000 mg/L. The viscosity decrease of profile control system is from 52000 mPa?s to 18000 mPa?s, or the percentage is 34.60 in 180 days. The results of core flooding indicate that the injection pressure gradient is 0.0565MPa/m and the breakthrough pressure gradient is 2.95MPa/m as the crosslinker including viscosifying B was injected at 11.36×10-3μm2 of core permeability. Weak gel evaluation proves that the favorable system includes urotropine of 200mg/L,resorcinol of 60mg/L, oxalic acid of 200mg/L and acid thickening agent B of 800mg/L with the viscosity at 76mPa?s.The aging time systemcould be longed as the 0.05% CDS-1 was solved.The apparent viscosity decrease of system is from 77.2 mPa?s to 55.2 mPa?s , or the percentage is 71.50 while the interfacial tension remains in magnitude of 10-2 mN/m at which the oil displacement efficiency can be obviously improved in 180 days. The optimization simulated show that (1)the procedure of the alternative injection of 0.05% CDS-1 solution&profile control was used as alternative frequency is six months and space treated of 12m. The profile control prepared with fresh brine, includes urotropine of 800 mg/L, resorcinol of 250 mg/L, oxalic acid of 350 mg/L and viscosifying B of 3000 mg/L.The oil increasement is 855263t or enhanced oil recovery over waterflood is 22.23% at 757m3/d of injection rate.(2) For CDS-1/weak gel flooding, the chemical slug size is 0.30 PV weak gel / 0.05% CDS-1 and the buffer size is 0.10 PV weak gel solution.The weak gel includes viscosifying B of 800 mg/L,urotropine of 200 mg/L,resorcinol of 60mg/L and oxalic acid of 200mg/L.The oil increasement is 786470t or enhanced oil recovery over waterflood is 20.44% at 757m3/d of injection rate.The investigation shows that the alternative injection of 0.05% CDS-1 flooding & profile control and CDS-1 / weak gel flooding which provide a reliable theoretical basis of enhancing recovery and execution program could be favorablely used to enhance oil recovery for Gao 30 .These could be considerd as a candidate for the similar high-temperature oil reservoirs which can enhance oil recovery to 20% OOIP. |
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