Treasure In The High-temperature, High Salt And Low Permeability Reservoir Surfactant Augmented Injection Technology Research

Petroleum crude is an important resource in this world.Actually,the requirement of crude increases with the economy in China.So some technologies are used to exploit crude oil,especially enhanced oil recovery(EOR)methods are done to recovery oil deeply in oilfield exploited.Baolang Oilfield belongs to a clastic rock reservoir with low porosity,low permeability,low porosity,ultra-low permeability and high temperature and high salinity,In experiments,the temperature is 99℃; the test solutions are prepared in the oilfield produced water of TSD=40000mg/L.where the overall physical property of the reservoir is poor and some of the wells had the phenomenon that more water injection was conducted,more difficulty was created in the process of water flooding.In consideration of the problem,water sensitivity of the reservoir rock is evaluated in laboratory experiments,the causes of poor water absorting in the injectors of the block are systematically analyzed,for the purpose of solving the problem,pretreatment techniques are developed for improving the water absorpting ability in strong water sensitivity reservoirs,by which the damage of injected water to the reservoirs can be reduced,the absorption ability to the injectors can be raised for ensuring the stable water injection in the oil field.Unfortunately,the technology is not investigated on low or ultralow permeability core(≤50×10^-3μm²)in laboratory so far.Usually,scientists and reservoir engineers think that the residual oil could not activated to be mobile in this situation because of the capillary resistance force for low or ultralow permeability cores being higher than that for medium or high permeability pore(≥50×10^-3μm²),or because of the pore diameter for low or ultralow permeability cores being smaller than that for medium or high permeability pore.As for the geologic condition of Baozhong block in Baolang oil field,Basis on it, author simply estimate and filter 18 kinds of surfactants author hade admeasured the equilibrium interfacial tension and dynamic interfacial tension of 18 different kinds of surfactant active agent,and selected an advisable surfactant active agent for Baolang oil field.After these experiments,the cloud point and the Krafft point be examinated. At last,The surfactants of 2 Sulfonates S-036/S-912 ration using in injectivity improvement was screened out through interfacial tension(IFT)and contact angel in this paper.The ultra-low IFT of 10^-3mN/m between the crude oil and surfactant brines were lowered at different injection/produced brine mixed and at 0.05% of surfactant concentration.The results demonstrate both the capillary force and contact angel were reduced favourablely,from 70°to 25°.Author also proceeded core simulation experiments on decreasing displacement pressure by surfactant and determining injection rate of surfactant in field.The result of experimental study shows that injecting surfactant system into cores can reduce injected pressure at different levels, the low surfactant concentration solution is also of ability in lowering pore resistance force in low or ultralow permeability sandstones due to wettability alteration so as to injection pressure being lowered while brine relative permeability being increased. The average pressure drop is 18.3% as brine relative permeability increases 10% for 12 core flooding tests.So it can offer a new method of blow-down stimulation in low permeability oilfield,high temperature and salinity reservoir.