Research and Application of Integrated Fracturing Fluid for Tight Sandstone Gas in Ordos Basin

The characteristics of Ordos basin is large vertical span, poor connectivity, small effective reservoir thickness, poor reservoir physical properties, low clay mineral content, small pore throat radius and low pressure coefficient. Fracturing technology must be used to realize effective development of this tight gas reservoir. In order to solve the problems of the current fracturing fluid system, the integrated fracturing fluid system is studied. A new thickener agent was prepared by emulsion polymerization of acrylamide, 2-acrylamide-2-methypropanesulfonic acid, acrylic acid and auxiliary agent-1.The experimental evaluation of viscosity increase, drag reduction, suspended sand, temperature and shear resistance, gel breaking, additive compatibility, anti-swelling and surface tension of integrated fracturing fluid system is carried out, and the field application effect of integrated fracturing fluid is analyzed. The results show that the viscosity of the integrated fracturing fluid system is flexible and adjustable. The viscosity increases with the increase of the concentration of the integrated thickener, and the viscosity adjustment range is 3−100 mPa \(\cdot\) s. The high viscosity liquid has excellent suspended sand performance, and the viscosity of 0.8% concentration integrated fracturing fluid is more than 60 mPa.s under the condition of \(60\,^\circ {\text{C}}\) and 100 S−1 shears. The drag reduction rate >70%, anti-swelling rate >70%, salt tolerance rate under standard salt water >40%. Surface tension <32 mN/m and the damage rate to shale formation was only 2.8%. Its integration is mainly reflected in functionality and application. In terms of function, it integrates slick water, linear glue and cross-linked hydraulic fracturing fluid system, which can meet the different requirements of tight gas reservoir fracturing reconstruction processes for fracture making, drag reduction, anti -swelling, sand carrying and rapid flow-back. The integrated fracturing fluid was used in 163 wells and 437 section. The average fracturing fluid of single section is 370 m3, the average sand addition is 51.4 m3, and the average sand addition strength is 6.9 m3/m. 84 gas wells were tested which the open flow rate was 71300 m3/d, the average daily production was 23900 m3/d. The integrated fracturing fluid promotes the tight gas fracturing process test, improves the fracturing effect, and shows good adaptability to all kinds of gas reservoirs and fracturing process.