Research and application of a novel flocculant combination in the treatment of fracturing flowback fluid

Abstract

A novel flocculant combination was developed for the treatment of fracturing flowback fluid of Linxing coalbed methane field, with polysilicic acid polymerized iron sulfate as the coagulant and acrylamide and acrylic acid-1,2-ethylenetriammonium chloride copolymer as the coagulant aid. The optimal conditions for flocculation treatment of gas layer fracturing flowback fluid were optimized and screened, and the flocculation mechanism was analyzed. The results showed that the best flocculation effect was achieved when the mass concentration of the agent was 300-400 mg/L, the pH was 7.5-8.5, the temperature was 25-35 ℃, the mixing strength was 1 300-1 500 s-1, and the flocculation time was 20-30 s. Under optimized conditions, the novel flocculant combination was applied to the Linxing coalbed methane backflow liquid treatment station. The suspended solids mass concentration in the effluent was stabilized at 6-8 mg/L, the oil mass concentration was stabilized at 3-5 mg/L, and the median particle size was stabilized at 1.4-1.7 μm. The effluent quality met the reinjection water control indicators at reservoir air permeability of [0.5, 2.0) μm2 of the Technical Requirements and Analysis Methods for Water Quality Indicators in Clastic Rock Reservoirs (SY/T 5329-2022). The effluent could be directly reinjected into the ground. The novel flocculant combination has broad prospects for application and promotion.

Keywords

• fracturing flowback fluid
• flocculation
• reinjection