Hydraulic Fractures from Non-Uniform Perforation Cluster Spacing in Horizontal Wells: Laboratory Testing on Transparent Gelatin

Abstract

The efficiency of a hydraulic fracturing treatment is directly related to the total surface area of the fractured formation. Development of design guidelines for selecting the optimal perforation cluster spacing, fracturing fluid type, rheology, and flowrate can help maximize well production following a hydraulic fracturing treatment for an arbitrary in-situ stress state, formation type, and other geomechanical properties. The influence of non-uniform spacing of perforation clusters along a horizontal wellbore on simultaneously-induced multiple fracture (multi-frac) growth into a reservoir formation was investigated by a series of laboratory-scale models. The relative geometry of the fluid-driven fractures generated in the models was compared to the relative spacing between three perforations.Uniform perforation spacing is found to yield more homogeneous multi-frac growth, as maximizing the spacing between all perforations minimizes multi-frac growth interference, compared to moving the second (middle) perforation closer to either the toe or the heel of the horizontal well. These results may be associated with parameters not considered by conventional theoretical modeling, such as the relative timing of fracture initiation, dominant (run-away) fracture creation, and inactive perforations. Incorporating these effects may promote more reliable predictive modeling of multi-frac propagation patterns, hence optimizing reservoir stimulation design. Analogue scaling comparing the laboratory conditions used with a typical field-scale hydraulic fracture treatment is then performed to assess the reliability of the conclusions.