Borate-based fluids have been widely used as fracturing fluids for hydraulic fracturing treatments for several decades. Although the fluid system had been studied extensively and the importance of shear recovery was fairlywell understood, the rate of shear recovery for different pumping conditions was still an issue in question. It was commonly believed that fluids crosslinked with borate had reversible shear recovery after exposure to pumping through tubing and perforations. As a consequence, fluids with inadequate shear recovery have been used, resulting in premature screenouts and unnecessary high polymer loadings. We will show that the shear recovery rate is influenced by several physical and chemical factors, such as temperature and pH. Based on the understanding, we have developed a novel fracturing fluid with much-improved shear recovery and simplified operational requirements.
We present the laboratory development of the novel fracturing fluid based on guar and a novel borate crosslinker. The crosslinker is a solid borate material, which allows controllable crosslinking through slow dissolution and instant shear recovery. We used a simple experimental method to study shear recovery behavior in the laboratory and field environment. The new fluid shows excellent compatibility with water sources used for fracturing treatments in western Siberia. The use of dry crosslinker also results in the reduction of polymer loading from 4.2 kg/m3 to 3.0 kg/m3leading to higher proppant pack conductivity. We also describe the field cases of the new fracturing fluid.
The new fluid has significant advantages over the existing technology because of better shear recovery, lower polymer loading, and operational simplicity. It is well suited for operational, logistical, and reservoir conditions in Russia.