Laboratory Investigation of Wellbore Integrity Under Hydraulic Fracturing Using a True-Triaxial Apparatus with an Integrated Monitoring System

Summary This study explores wellbore integrity under hydraulic fracturing conditions by integrating a true-triaxial testing apparatus with advanced monitoring techniques, including Distributed Strain Sensing (DSS), Acoustic Emission (AE), and a self-developed laboratory-scale cement bond evaluation device to comprehensively assess Cement Bond Log and Variable Density Log (CBL/VDL) responses. Homogeneous cement specimens were utilized in experiments designed to mimic realistic field fracturing procedures, incorporating multistage cyclic loading, perforations, and high injection pressures. Fiber-optic cables embedded along the external surface of the rock samples provided continuous, high-resolution strain data, while AE sensors captured acoustic signals associated with fracture initiation and propagation. The primary objective was real-time monitoring and precise control of fracture propagation to prevent unintended rapid fracture extension beyond targeted boundaries, which could result in pressure loss and interfere with the intended experimental design. The integrated application of DSS and AE monitoring delivered comprehensive, real-time insights into fracture behavior, including fracture propagation dynamics and evolving morphology. Additionally, the laboratory-scale cement bond evaluation device enabled a detailed assessment of wellbore stability before and after fracturing, offering critical guidance to enhance cement sheath design and optimize well completion strategies for high-pressure hydraulic fracturing operations.