Mechanical properties of polycrystalline tetrahydrofuran hydrates as analogs for massive natural gas hydrates

Abstract For experiments simulating marine sediments that include massive hydrate crystals for geotechnical stability assessment and for development of hydrate recovery techniques for such natural gas hydrate deposits, mechanical properties of massive natural gas hydrate crystals must be assessed as important factors affecting geotechnical stability for submarine hydrate deposits. This report describes mechanical properties of polycrystalline tetrahydrofuran hydrates of two types as analogs for massive natural gas hydrates. All tetrahydrofuran hydrate specimens exhibited brittle failure under uniaxial compression, similarly to reported massive natural gas hydrates. The uniaxial compressive strength of transparent massive hydrate specimens solidified by cooling aqueous tetrahydrofuran solution with small subcooling was 2.8–4.3 MPa. Its elastic modulus was approximately 800–1300 MPa. The strengths of cloudy massive hydrate specimens prepared from a slurry in which fine hydrate crystals were dispersed at higher subcooling were 5.3–5.7 MPa. The specimens’ elastic moduli were approximately 400 MPa. Comparison with the reported mechanical properties of massive natural gas hydrates showed that the strengths of tetrahydrofuran hydrate specimens have good agreement with the strengths of natural ones, significantly higher similarity to natural specimens was found for transparent specimens. Regarding the elastic modulus, cloudy specimens showed higher similarity to the natural specimens. The transparent specimens showed elastic modulus values that were a maximum 4.6 times higher than the natural ones.