Properties of thermal insulation materials for deep oil and gas in situ temperature-preserved coring: A focus on interphase

The high-temperature conditions of deep oil and gas reservoirs notably affect the porosity and permeability of rocks. In situ temperature-preserved coring (ITP-Coring) technology is crucial for accurately assessing rock properties in deep reservoirs. High-performance thermal insulation materials are crucial for supporting ITP-Coring during deep oil and gas exploration. This study explores the impact of high-temperature and high-pressure (HTHP) conditions on hollow glass microsphere/epoxy (HGM/EP) thermal insulation materials, focusing on the interphase. Investigations of HGM/EP materials with varying hollow glass microsphere (HGM) strengths and volume fractions reveal that elevated temperatures cause the molecular chains of the epoxy resin matrix to relax, leading to matrix softening and a decline in mechanical properties. Additionally, high-pressure water infiltrates the material, damaging the interphase and HGMs, further compromising material performance. The combined HTHP environment accelerates this degradation. Dynamic mechanical analysis (DMA) shows that S60HS HGMs, which possess higher strength, interact more strongly with the matrix and exhibit higher entanglement density, resulting in superior interphase adhesion. This enhances stress transfer efficiency and reduces the loss of storage modulus at the interphase. Theoretical analysis indicates that the interphase thickness and modulus of S-f40 remain mostly unaffected after HTHP treatment, with values higher than the epoxy matrix. This correlates with DMA results, demonstrating that S-f40 has the smallest adhesion factor ( A ), indicating the highest interfacial stress transfer efficiency. S-f40 also exhibits optimal thermal conductivity and mechanical properties, making it ideal for ITP-Coring in deep reservoirs. These findings provide insights for optimizing materials in HTHP environments for deep reservoir exploration.