| At present,the old oilfields in eastern China are in the stage of extra high water cut development,and the situation of oil stabilization and water control is very severe.It is urgent to take measures to improve recovery efficiency greatly.Practice has shown that the polymer flooding technology can significantly improve the recovery of water flooding reservoirs,and polymer flooding in Daqing Oilfield has enhanced oil recovery over 10%.With the application scale of polymer flooding gradually expanded,the remaining oil reserves of ordinary oil reservoirs have gradually decreased,and the remaining oil in high-temperature and high-salt reservoirs has gradually become the target of polymer flooding.Due to temperature resistance and salt resistance of the existing polymer is difficult to meet the actual needs of the field,the development of new temperature-resistant and salt-resistant polymer has gradually attracted extensive attention of petroleum scientists.This paper takes polymer material science,physical chemistry and reservoir engineering as the theoretical guidance,instrument detection,chemical analysis and physical simulation as the experimental means,and takes the geological characteristics and fluid characteristics of Bohai reservoir as the simulation object.Therefore,this paper has carried out the physical simulation research and action mechanism analysis of the"temperature-salt dual-response"polymer flooding effect.The results showed:(1)With the increase of temperature,the viscosity of"high molecular"polymer solution and salt-resistant polymer solution is decrease,and the viscosity of"temperature-salt dual-response"polymer solution shows a change trend of"first decreasing and then increasing",and the temperature sensitive inflection point appears near the temperature of 75?.Meanwhile,compared with"high molecular"polymer and salt-resistant polymer,"temperature-salt dual-response"polymer has better salt-resistance.(2)With the increase of temperature,the size of molecular aggregates in the"high molecular"polymer solution increases slightly,the size of molecular aggregates in the salt-resistant polymer solution increases,and the size of molecular aggregates in the"temperature-salt dual-response"polymer solution increases significantly.It can be seen that the hydrophobic monomer on the polymer molecular chain causes intermolecular cross-linking or association of the polymer,and the formation of regional network structure is the main reason for the temperature resistance and salt resistance of the"temperature-salt dual-response"polymer.(3)The increase in temperature leads to the increase in the retention amount of"temperature-salt dual-response"polymer solution in porous media,and polymer retention causes seepage resistance and increased injection pressure,and the injection pressure rises much higher than the value for the"high molecular"polymer solution.(4)When the concentration of polymer solution CP=1500 mg/L and the reservoir temperature is 65?,the lower limit of permeability of"temperature-salt dual-response"polymer solution is about1500×10-3?m2 and the lower limit of permeability of"high molecular"polymer solution is about 500×10-3?m2.When the concentration of polymer solution CP=1500 mg/L and the reservoir temperature is 85?,the lower limit of permeability of"temperature-salt dual-response"polymer solution is about 3000×10-3?m2.(5)When the temperature increases from65?to 85?under the condition of homogeneous core,the relative increase in the recovery efficiency of"high molecular"polymer flooding is-1.1%,and the relative increase in the recovery efficiency of"temperature-salt dual-response"polymer flooding is 1.4%.When the temperature is 85?under the condition of heterogeneous core,the relative increase in the recovery efficiency of"temperature-salt dual-response"polymer flooding is 15.5%,and the relative increase in the recovery efficiency of"high molecular"polymer flooding is only 3.6%.(6)Compared with"high molecular"polymer,the increase in temperature leads to enhanced intermolecular association in"temperature-salt dual-response"polymer solutions,the physical cross-linked network structure increases,the retention increases,and the retention causes the increase of seepage resistance and injection pressure,and the effect of expanding the swept volume increases,so the increase of recovery efficiency increases. |
PDF Full Text Request