Study on Reuse of Fracturing Fluid in Oil and Gas Fields in Northeast China

Large amount of fracturing fluids recovered during fracturing jobs in oilfields in northeast China imposed serious contamination to the environment and the cost spent in the purification of the fluids was high. A portable waste water disposal equipment was developed in an effort to reuse these fluids. A used clear fracturing fluid and a used guar gum fracturing fluid were disposed of with this equipment, and the produced fluids were analyzed with a laser particle size analyzer (Model: Master sizer 2000), showing that more than 99% of the particles in these fluids had been removed, while large amount of calcium and magnesium ions were found in the fluids after water analyses. Fracturing fluids used in the Well Bei201 had borate ions that were difficult to remove and reacted with HPG base fluid to form a viscous gel. The calcium and magnesium ions in the fracturing fluids caused the CMG to lose its function as a thickening agent. Based on these analyses, an optimum fracturing fluid formulation was developed using the reused disposed fracturing fluid:0.5%BCG-1+0.2%B-43+0.3%BCG-5+0.1%B-13+0.4%B-55, which was a non-crosslinking fracturing fluid. The new formulation had viscosity greater than 30 mPa·s after shearing 120 min at 120 ℃ and 170 s^-1, settling speed of falling ball less than 0.324 mm/s, viscosity of the gel-broken fluids less than 5 mPa.s, and residue content of the gel-broken fluids less than 30 mg/L.