Study on the Stimulation Effectiveness Evaluation of Large-Scale Hydraulic Fracturing Simulation Experiment Based on Optical Scanning Technology

Abstract

Summary Unconventional reservoirs such as gas shales and tight gas sands require technology-based solutions for optimum development because of the undeveloped matrix pores and poor permeability. Hydraulic fracturing is one of the most critical technologies. The quantitative characterization of hydraulic fractures is of great significance to the stimulation evaluation of the reservoir, but there is still a lack of fine, effective and systematic evaluation methods. 3D optical scanning technology is widely used in the quantitative characterization of rock fracture morphology for its advantages of high speed, convenience, high precision, and nondestructive testing. In this study, after the indoor hydraulic-fracturing simulation experiments, 3D optical scanning was used to visualize the fracture network. On this basis, two aspects of quantitative evaluation methods for stimulation effectiveness were established, including: (1) evaluating the local conductivity (permeability) of different fractures by cutting hydraulic-fracturing samples. Then combining local conductivity of different fractures with the overall stimulated reservoir area, which could be more reasonable to evaluate the stimulation scope of the reservoir; (2) calculating the fractal dimension (FD) of the 3D spatial structure based on the point-cloud processing, which could directly reflect the complexity of the fracture network. Finally, a new evaluation index for stimulation (Es) was established to comprehensively assess the stimulation effectiveness of the reservoir, which was applied and verified through the indoor fracturing simulation experiments of tight sandstone from the Ordos Basin, China.