Development of Guar-Based Crosslinked Fracturing Fluid in Flow-Back Water

Abstract

Strict regulatory is now required for storage, handling, and less environmental effect for the fracturing fluid. Therefore, it is desirable to reuse the flow-back fracturing fluid without discharging to environment. We studied a new guar-based crosslinked fracturing fluid in flow-back water. The main challenge for crosslinking guar in the flow-back water is the residues of crosslinker and oxidative breaker. These residues inhibit the solubilization of guar and decrease viscosity of fluid or break the fluid. In addition, these residues can locally crosslink guar in the fracturing fluid and affect the properties of fracturing fluid. A new crosslinker of high-molecular-weight polyboronate was hereby developed. It has properties of crosslinking sequentially, buffering pH decrease and strong sequestering ability. Hence, it can enhance the viscosity of the fluid contained residues crosslinker and breaker in flow-back water. The new crosslinker can be used to crosslink guar fracturing fluid with produced water, fracturing flow-back water, acidizing flow-back water and sea water. The high salinity flow-back water can be treated simply by precipitation and flocculation of solid particles. There is no need to remove soluble salts. Clay stabilizers such as KCl and organic cationic compounds were not needed for fracturing fluid by using the high salinity produced water. Hence, the cost of fluid was also reduced with no additional clay stabilizers.The new fracturing fluid in high salinity water is also high temperature stable. A typical fracturing fluid can be stable up to 130 °C with 0.45% hydroxyl propyl guar at 86,420 mg/l total dissolved solids. The viscosity of fracturing fluid can be maintained above 50 mPa.s for 2 h at 170 s−1 and 120 °C. The new crosslinked fracturing fluid in high salinity water has low friction pressure, good compatibility with reservoir and high proppant suspension ability. The new fracturing fluid with the treated flow-back water has been successfully used in Sulige gas field.KeywordsGuarFracturing fluidFlow-back water