长庆低渗透油田注水水质稳定技术

Technology for controlling injection water quality in Changqing oil field

长庆油田是低渗、特低渗透油田。注水水质是影响注水开发效果的重要因素之一。长庆油田主要以洛河层水为注入水 ,影响水质的因素中 ,主要因溶解氧及硫酸盐还原菌产生腐蚀性 ,固体颗粒含量和粒径对低渗透砂岩造成严重伤害。注入水与地层水普遍不配伍 ,垢型以BaSO4、CaCO3 为主 ,垢量最大可达 2 .3g/L ;注水层大多为弱速敏、弱水敏 ,但长 2层普遍存在中等偏弱到中等程度的水敏。通过室内试验及现场实施适合于长庆油田的除 (隔 )氧、精细过滤、注入水杀菌防腐、防治注水地层结垢、水敏地层防水敏等注水水质稳定技术 ,为长期稳定注水从而提高油田注水开发效果提供了技术保障。

Changqing oil field is a low and extra low permeability oil field developed mainly under waterflooding. The injection water quality plays an important role in oilfield development. Based on the geologic conditions and research and practice on injection water quality controlling technology of this oil field, this paper discussed the factors, which have effects on oilfield water injection, such as corrosion, scale, plugging, water sensitivity, etc. The corrosion of injection water in Changqing oil field is mainly caused by dissolved oxygen and SRB cell. The low permeability reservoirs of Changqing oil field will not be damaged when the content and mean diameter of particle in injected water are below 1mg/L and 1μm respectively. The injection water, which is generally not matched with formation water, will form scale if it gets into the strata. The styles of scale are mainly BaSO 4 and CaCO 3. The injeition intervals are mostly slightly water sen sitive and velocity sensitive strata, but Layer Chang 2 commonly presents slightlymiddle to middle water sensitivity. Through the laboratory and field experiments, some techniques which are suitable for Changqing oil field, such as, oxygen removing and fine filtration, sterilization and corrosion prevention for injection water, scale prevention for water injection formation, water sensitivity controlling to water sensitivity formation and injection water quality control, etc, are developed.