Indicators for preparing fracturing fluid with reused produced water from coalbed methane wells

A large amount of water will be produced during the production process of coalbed methane. In order to address the challenges of difficult treatment and high processing costs of produced water, a case study was conducted in Anze block of the Qinshui Basin. After fracturing of coalbed methane wells with active water, continuous monitoring of ion salinity in produced water, stability evaluation of produced water, and compatibility assessment of produced water in preparing active water fracturing fluid were carried out. The experiments show that the fracturing fluid quickly mixed with the coalbed water upon injection and rapidly flowed back after fracturing. It took approximately 72 hours for most of the fracturing fluid to flow back from the coal bed. At least 48 hours were required for the produced water from the coal bed to become clear and stable. The solid phase content of the produced water was less than 50 mg/L, meeting the standard of solid phase content for repeated use in fracturing. The fracturing fluid prepared by produced water is well compatible with formation water, with no precipitation or flocculation after mixing, minimizing reservoir damage. Utilizing produced water from coalbed methane wells to prepare fracturing fluid is feasible. A settling pond was designed for on-site treatment of produced water, which enables full recycling of produced water and significant savings in water treatment costs, thereby achieving cost reduction and efficiency improvement.