Experimental Research on Multi-Scale Micro-Fractures Channeling Model

Abstract The sustained annular pressure (SCP) in complex oil and gas wells, such as high temperature high pressure gas wells and gas storage wells, directly affects the safe production and lifecycle. The failure of wellbore integrity in SCP well is hard to observe, and the multi-scale channeling paths are difficult to be measured through logging. Therefore, it is necessary to establish a multi-scale channeling experimental platform. By studying controllable micro-fracture prefabrication technology, batch processing of cements with specific micro-fracture height is achieved. The relationship between channeling flow rate and pressure loss in cement stones with different micro-fracture height is determined, and the equivalent relationship between micro-fracture height and comprehensive equivalent permeability is inverted. A multi-scale micro-fracture channeling model is established based on two main channeling types: macroscopic gas flow in micro-fracture channels and gas seepage in weakly cemented channels. The model is refined using multi-scale channeling experimental data. The research results enable quantitative analysis of annular pressure test data and prediction of annular pressure, providing a basis for reducing casing pressure risks and optimizing wellbore integrity design.