Intersecting-Contact Sealing Mechanism Analysis and Experimental Investigation of Pressure-Preserved Coring Controller in Deep Coal Seams

Pressure-preserved coring enables in situ encapsulation of deep coal samples at the borehole bottom. By effectively reducing gas desorption, it supports reliable reserve assessment. Achieving reliable pressure-preserved sealing within the confined space of drilling tools remains a critical technical challenge in the field. Focusing on the pressure controller, this study investigates three key aspects: configuration design, sealing interface behavior, and structural performance. The investigation employs both theoretical modeling and laboratory experiments. First, a geometric configuration design methodology was proposed for the pressure controller using intersecting contact and tapered sealing principles. This was followed by the creation of a spatial motion interference prediction model for the assemblies. Secondly, the contact behavior of intersecting sealing interfaces was studied; analysis of the failure mechanisms showed that the design achieves a pressure-preserved capacity of about 24 MPa. Finally, laboratory tests validated the sealing performance of the pressure controller. The tests confirmed that seal ring failure is characterized by high-pressure extrusion, which is caused by an increased sealing clearance. The research findings elucidate the sealing formation mechanism of the pressure controller, establishing a theoretical foundation for advancing pressure-preserved coring technologies in coalbed methane and gas hydrate exploration and development.