Countermeasures for Comprehensive Control of Under-injection Wells in Chang 8 Ultra-low Permeability Reservoir

Chang 8 reservoir in Changqing Oilfield Jiyuan Liumaoyuan Block of Changqing Oilfield was a typical ultra-low permeability reservoir,the average permeability was below 0.3mD in the block.The block was put into water flooding in 2009,water injection pressure was over 20MPa at initial injection stage,and some injection wells have not met the requirement of allocation injection for a long time,after the stimulation of fracturing and acidizing,it was still in under injection state.There existed abnormal high pressure in the block,injection pressure exceeded 22.5MPa,it caused mpact on the long-term and stable production.In consideration of the situation,the countermeasures of comprehensive control of injection wells was studied.Through the research and development of new antihypertensive drag reducer for the overall pressure reduction,suitable measures were selected for ultra-low permeability reservoir and single well augmented injection technology and local pressure boosting,problems of ineffective wells and local abnormal pressure caused by water injection were solved.Good results are achieved in field tests,the problem of less injection in 55 wells is solved,daily augment injection is 998m3,it effectively solve the problem of high-pressure injection in ultra low permeability reservoirs,it provides a new idea and reference for water injection at high pressure in ultra-low permeability reservoirs.