Weighted Clean Fracturing Fluid for Deep Well Stimulation

High temperature borate cross-linked guar gum fracturing fluids have long been used in fracturing deep,low permeability and high temperature reservoirs.High friction and the difficult-to remove residues of the fracturing fluids are two problems that have to be faced with in the fracturing jobs.A thickening agent,with acryl amide and ionic functioning groups as the molecular backbone,is developed for use in fracturing fluid.It has a certain degree of hydrolysis.A weighted clean fracturing fluid,BCG-1,has been formulated using this thickening agent and other additives carefully selected.In laboratory experiments,BCG-1 demonstrated good high temperature and shear resistance performance.The viscosity of BCG-1 maintained at 57 mPa·s or higherafter shearing 120 min at 160℃ and 170 s^-1,and good repeatability of the experiments can be obtained.Friction test on 8 mm flow tubes reveals that ZJFA-1,an extender for the fracturing fluid,greatly reduces the friction of BCG-1.NaNO₃ as a weighting agent has almost no effect on the friction of BCG-1.BCG-1,after gel-breaking,has a viscosity less than 21 mPa·s,and residue content less than 5 mg/L,characteristic of clean fracturing fluid.