Synthesis Of Crosslinker For High-temperature Guar Based Fracturing Fluid And Characterization Of Hydraulic Fracturing Fluid

Hydraulic fracturing techniques are widely used to enhance oil and gasproduction from subterranean formations. The fracturing fluid is a critical componentof the hydraulic fracturing treatment. Its main functions are to open the fracture andto transport propping agent along the length of the fracture. Because of their low cost,high performance and ease of handling, water-base fluids are the most widely usedfracturing fluids. Guar based fracturing fluids are the most commonly used fluids inreservoir stimulation. With the increase of reservoir temperature and emphasis onformation damage，therefore, it is important to do the research on the developmentfor crosslinker to prepare high-temperature and low formation damage guar basedfracturing fluid, as crosslinker is a significant component of hydraulic fracturing fluid.The organic borate crosslinker was synthesized, which not only preparedconventional concentration guar based fracturing fluids with excellent thermalstability property, also crosslinked low concentration guar prepared well thermalstability property, shear performance and formation damage fracturing fluids. Thecontents and conclusions are as follows:1. The organic borate crosslinker was synthesized by two organic ligands. Theeffects of various factors on the properties of crosslinker and fracturing fluids werestudied. The optimum synthesis conditions and composition were obtained. The besttemperature of0.4%guar based fracturing fluid was up to146℃and fracturing fluidmaintains viscosity above140mPa·s after shearing at120℃in60min.2. The low concentration guar based fracturing fluid crosslinked by organicborate crosslinker was prepared, and the rheology of fracturing fluid wascharacterized. The results show the best temperature of low concentration guarfracturing fluid is up to135℃, fluid maintains viscosity about80mPa s aftershearing at120℃in60min. And viscoelasticity and filtration properties of lowconcentration guar based fracturing fluid satisfy fracturing requirements.3. Gel breaking performance and compatibility of low concentration guar basedfracturing fluid were evaluated. The results showed: low concentration guar basedfracturing fluid is completely gel broken at95℃,1.0‰ammonium persulfate about 50min. Adding cleanup agent can effectively reduce the surface tension of thefracturing fluid. The amount of low concentrations guar based fracturing fluid residueis reduced to328mg/L from562mg/L. The distribution of the residue particle sizesare mainly concentrated was20~200μm, and volume average particle diameter is76.028μm, which cannot enter stratigraphic throat. Adding a little amount ofdemulsifier in the fracturing fluid can significantly improve the compatibility offracturing fluid with formation fluids.