Research Of Deep Acidification Technology In Injection Wells Of Qijiabei Oil Field

Qijiabei oilfield is a typical heterogeneous sandstone reservoir with low porosity, lowpermeability and low productivity. In recent years, part of water injection wells face thedifficulties of injection pressure increasing fast and water absorbing difficulty. In order to reduceinjection pressure rising rate and improve the water absorption in water injection well, meanwhileavoiding the weakness of that the acid/carbonate reaction is too fast and effective acid reaction hasa very small range. It is necessary to research deep long-term acidification technology in injectionwells for this type of reservoir in order to expand the scope of acid liquid, reduce injectionpressure and improving water flooding effectiveness.According to the types of heterogeneous sandstone reservoir with high temperature, lowpermeability in Qijiabei oilfield, select hydrofluoric acid, hydrochloric acid, fluoroboric acid andacetic acid as the main agents of acidizing fluid. Developed composite retardant in order to reducethe rate of acidic-rock reaction, increase the operating range of acid liquid. Developed compositeadditives in order to avoid the corrosion of downhole equipment and reduce the damage of thereservoir. Process parameters has been optimized by evaluating the injection scheme, laying thefoundation of acidizing reservoir uniformly. Research shows that, this developed formula systemhas permeability improving rate of23.88%on natural core and corrosion rate on the standard N80steel sheet of0.488g/(m2h), suggesting good characteristics of corrosion inhibition, retardationand permeability increasing.