Sealing Form and Failure Mechanism of Deep In Situ Rock Core Pressure-Maintaining Controller

The mechanical properties of deep rocks change nonlinearly in an in situ pressure environment, so standard cores cannot be used as real samples for deep rock mechanics research. Therefore, obtaining an in situ pressure core is essential. However, the existing pressure-maintaining cores cannot overcome the sealing capacity limit, largely due to the lack of consideration of sealing theory and experimental verifications of pressure-maintaining controllers. Therefore, this paper explores the sealing form and failure mechanism of pressure-maintaining controllers. The sealing state transition, pressure leakage, deformation failure theory, and test method for a pressure-maintaining controller are determined. Through theoretical analysis and experiments, (1) a seal-form discrimination method based on the chimeric curve is proposed to obtain the pressure seal conversion trend; (2) the leakage rate is exponentially related to the initial pressure, which confirms the pressure leakage principle of the pressure-maintaining controller; and (3) based on deformation failure theory for pressure-maintaining controllers, the failure mode and deformation trend are obtained through a destructive limit pressure experiment. The research results provide a theoretical basis and experimental support for improving pressure coring in deep rock and obtaining pressure cores at deep positions to construct a new conceptual system of deep in situ rock mechanics