Design of a high-performance pressure-preserving controller for in situ pressure-preserving coring in deep oil and gas extraction

Pressure-preserving controllers (PPCs) are crucial components of in situ pressure-preserving coring (IPP-Coring) devices for deep oil and gas extraction, and their ultimate pressure-bearing (UPB) capability determines the upper limit of their ability to acquire oil and gas reserves. However, due to the UPB-capability and sealing challenges, the working pressure typically does not exceed 70 MPa. In this study, the optimal design of a PPC using a self-developed IPP-Coring test platform is presented, and its seal failure mechanism is revealed. Experimental results demonstrate that the designed saddle-shaped PPC achieves a minimal UPB-capability of 140 MPa, which is twice the highest value reported in literature. A numerical simulation method was developed to predict the UPB-capability of the PPC, and its reliability was validated in comparison with experimental results. The simulation results indicate that the sealing failure of the PPC is attributed to a progressive escalation in seal clearance between valve cover and seat, which causes an O-ring extrusion. Under ambient temperature and ultrahigh pressure, the critical threshold for seal clearance in PPC seal failure is approximately 0.2 mm. These results provide significant insights into enhancing deep resource acquisition capabilities.