Study of fluid system for pressure reduction and injection of long-term injection wells in sensitive reservoirs

Abstract

Due to the sensitivity of the reservoir itself and the aggravation of reservoir damage caused by long-term water injection in a sensitive reservoir of a block in northwest China, the phenomenon of high wellhead pressure and water injection difficulty of new injection Wells is presented in different degrees. Based on the analysis of the effect of increasing injection measures in each stage, combined with the analysis of the cause of reservoir scaling and the sensitivity of long-term water injection volume flow, a new composite treatment liquid system was developed. The system integrates the secondary precipitation inhibition technology, anti-expansion and shrinkage composite technology, deep acidification technology and foam composite acidification technology, and achieves the dissolution rate of the main treatment solution of 22.5%, can maintain a low pH for a long time, and meet the long-term scale inhibition rate of 84.89%. In the evaluation of the core flow experiment, the core permeability recovered and increased after the treatment of the working fluid system, and achieved a good effect of plugging removal and injection increase in the field practical application.