Impact of perforation parameters on fracturing of glutenite reservoirs

Glutenite reservoirs are characterized by large stress differences and high fracture pressures, leading to great difficulty in fracturing, and how to reduce fracture pressure is the key to safely fracture the reservoirs. Mix cement and quartz sand in a ratio of 3∶1 and randomly mix different diameters of pebbles and fine gravel particles, to prepare artificial glutenite with side length of 300 mm, which were then perforated with hydraulic sand jet gun. By changing the angle from 0 to 90° and the depth from 1.5 to 6 cm, on-site different perforation azimuths and perforation depths were simulated. Based on field data, the three-axis stresses were set to be 9.4, 19.3 and 24.8 MPa, respectively. And then, a displacement of 50 mL/min and (fracturing fluid with) a viscosity of 45 mPa·s were selected to perform indoor hydraulic fracturing experiments, to analyze the effect of perforation angle and depth on fracture initiation and fracture pressure. The research results show that when the angle between the perforation direction and the horizontal maximum principal stress is 0°, the fracture pressure is the lowest at 11.9 MPa. And reducing the perforation azimuth can reduce the fracture pressure by 3.55 MPa, while increasing the perforation depth from 1.5 cm to 6.1 cm reduces the fracture pressure by 4.63 MPa. When gravel is present near the perforation, the fracture pressure increases abnormally by about 10 MPa. It is recommended to optimize the perforation azimuth, increase the perforation depth appropriately, and select the intervals with smaller gravel particle size and better selectivity for construction to improve the success rate of fracturing. The research results may provide a basis for selecting parameters in optimizing perforation schemes for Mahu glutenite reservoir.