Diverter plugging pattern at the fracture mouth during temporary plugging and diverting fracturing: An experimental study

Fracture mouth temporary plugging and diverting fracturing (TPDF) technology refers to plugging the previously created fractures by use of the degradable diverters and enhancing the wellbore pressure. In this way, the subsequent injection fluids can be diverted into the under-stimulated zone and the overall stimulation effects can be improved. Influenced by downhole temperature, pressure, and fracture mouth morphology, the reported slot plugging test at room temperature cannot effectively guide the field operation of the fracture mouth TPDF, and the success rate can be significantly influenced. In this work, a high-pressure evaluation system for fracture mouth temporary plugging is designed, the effects of the reservoir temperature and the real fracture morphology can be considered effectively. The key factors and their influencing pattern are systematically investigated. Moreover, the optimal temporary plugging condition and the key factors affecting the plugging effect were determined by orthogonal experiments. The results show that the diverter bridging speed at 150 °C increases by 33% compared with that at room temperature, and the corresponding diverter dosage reduces by 34%. If the diverter concentration is too high, the diverter bridging speed will be reduced and the diverter dosage will be increased. The higher the fluid injection rate and the carrier fluid viscosity, the faster the diverter bridging speed (DBS), and the less the diverter dosage. The factors influencing the diverter dosage rank (from strong to weak): the viscosity of the carrying fluid, the reservoir temperature, the fluid injection speed, the concentration of the 1 mm particulate-shaped diverter (PSD), and the concentration of the 3 mm PSD.