Low To Medium Permeability Oilfield Betaine Binary Oil Displacement Effect Research

Low to medium permeability reservoir H block in longdong Jurassic has entered thehigh water cut stage of oilfield development, this block has conspicuous contradictionsamong layers, increased high difficult of waterflooding development, and high formationsalinity, Affected by sedimentary environment, the block contain different degree of naturefracture, further aggravating the heterogeneity of the reservoir. The conventional secondarywaterflooding oil production technology is difficult to employ the low to mediumpermeability reservoir that is characterized by severe heterogeneity, lead to a lot of crude oilresorted under low to medium permeability reservoir after waterflooding. So, a kind ofdisplacement that has better property and capable of salt resistance is needed to exploit the oiland gas resources in the low to medium permeability reservoir, it can reduce the oil and watermobility ratio, so as to expand the volume of involving and enhance oil recovery.This paper under the guidance of modern reservoir engineering theory, physicochemicaltheory, advanced instrumental analysis and core flooding tests, base on the theoreticalcalculation of the H block pore radius and the gyral radius of polymer molecule test, themolecular of1600×104French SNF salt resistance polymer is suitable and sulfo betaineresistance to salt surfactant is suitable for H block to enhance oil recovery, and studied theflow of the binary system performance, viscosity, oil-water interface, system stability and itsinfluencing factors of binary system. Select berea core that is very similar to H blockreservoir physical properties, the binary composite system of alkyl betaine oil displacementexperiment were processed respectively, such as polymer concentration, surfactantconcentration, injection rates, slug combination. The result showed that polymer andsurfactant concentration had different effects on chemical recovery of binary compositesystem, and the polymer concentration had great influence, when the polymer concentrationwas1400mg/L and surfactant was0.2%, the binary composite system to enhance thechemical recovery was very obvious; the injection rates of binary composite had effect of itrecovery, the injection pressure rose with the increase of the injection rare, can expanding thesweep volume; under condition of same injection volume of chemical, major slug plussubslug and protection of the slug injection pattern of oil displacement effect is better than thegeneral single slug; the chemical recovery had rose with the increase of the major slug size,when the major slug size was0.5PV, it chemical recovery was growth slow. Utilizing theoptimized binary composite system had carried on oil displacement effect verification test in H block natural core, the result showed that the screening of the binary composite system hadexcellent matching with the longdong Jurassic reservoir, it could meet the requirement ofcarry binary composite flooding in low to medium permeable fracture reservoir, and theenhance recovery rate is around15%.