Self-sealing control principle and technology of in-situ temperature pressure preserved coring for deep oil and gas

Accurately evaluating the quality and scale of deep oil and gas reservoirs is the key to effectively exploring and developing deep oil and gas resources. Changes in temperature and pressure can cause significant variations in key reservoir quality parameters, such as porosity, permeability, and saturation, leading to distortions in oil and gas reserve assessments. To addresses the technical bottleneck of the existing pressure-preserved coring systems, which has a pressure-preserved capacity not exceed 70 MPa due to the limitations of small coring space, a complex coring environment, significant disturbance during the coring process, and the difficulty in controlling coring operations, a self-sealing control principle and method for pressure-preserved coring was proposed. The sealing structural parameters of the pressure-preserved controller (PPC) under high temperature (150 °C) were optimized through experiments and numerical simulations, the sealing failure mechanism was thoroughly revealed, and the pressure-preserved capacity of the PPC under high temperature was enhanced from 100 to 140 MPa. In addition, to achieve the temperature preservation of the core in the deep oil and gas environment, a temperature preservation system combining active and passive temperature preservation was designed and integrated into the deep oil and gas in-situ temperature pressure preserved (ITPP) coring system. Finally, the coring function and temperature pressure preserved capacity of the ITPP coring system were verified through field and laboratory tests. The results show that the developed ITPP coring system can successfully achieve the temperature pressure preserved function, and can sample oil and gas-bearing core samples with a diameter of 50 mm and a maximum length of 1000 mm from wells up to 5000 m. This study addresses the urgent need for reliable and effective pressure-preservation in deep oil and gas exploration.