Impacts of additives in hydraulic fracturing technology: an experimental investigation in the Sulige Gas Field, China

In the process of hydraulic fracturing, significant quantities of fracturing fluid with complex additives are pumped into tight reservoirs, resulting in a series of interactions that alter the water quality of flowback fluid and affect reservoir properties. This study focused on the impacts of additives on fracturing fluid-tight sandstone interactions by conducting experimental investigations with five typical additives, including pH control agents, bactericide, crosslinker, surfactant, and clay stabilizer. The characteristics of tight sandstones and additives, additive-tight sandstone interaction processes, and the impacts of additives on fracturing fluid-tight sandstone interactions were studied using X-ray fluorescence (XRF), X-ray diffraction (XRD), Scanning electron microscope (SEM), and hydrochemical analyses. The results indicate that the tight sandstones in the study area primarily consist of quartz (45.9% to 81.6%) and clay minerals (16.5% to 47.4%), with widespread kaolinite and chlorite. Halite and calcite dissolution, as well as ion exchange between Na⁺ and Ca²⁺, were observed during additives-tight sandstone interactions. Among the five additives, bactericide, clay stabilizer, and surfactant have low ion content and demonstrate a dissolution effect on rock minerals. The pH control and crosslinker significantly influence the chemical components and aquatic environment of fracturing fluid, exerting a more substantial impact on the fluid-rock interactions. Their strongly basic environments are detrimental to the stability of kaolinite crystals, as well as they also facilitate the precipitation of calcium-containing minerals (e.g., calcite and fluorite). This study provides insights into geochemical processes during hydraulic fracturing and offers guidance for optimizing fracturing operations to minimize formation damage and contaminants in flowback fluid.

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