Weakly cemented similar materials for in-situ desanding research on solid fluidization exploitation of natural gas hydrate

In the process of natural gas hydrate (NGH) trial production by means of solid fluidization exploitation (SFE) and depressurization, the trial production was interrupted due to severe sand removal. In-situ sand removal is an effective solution. However, it is very difficult to directly use real or synthetic weakly cemented NGH materials to conduct the experiment of in-situ desanding. This work prepared the weakly cemented similar material particles (WCSMPs) that employed hydrophilic polyethylene (PE) and quartz to simulate hydrate and argillaceous silt respectively. The mechanical strength of WCSMPs was adjusted using cement as the adhesive and by adding chloride salt solutions to enhance the hydration of the cement. The microscopic pore structure and cementation state of WCSMPs were observed by SEM and MIP. Splitting test and triaxial compression test were used to explore the effect of the chlorine salt type, weight ratio of salt to cement (Msalt/Mcement), material ratio, and curing age on the mechanical properties of WCSMPs, such as tensile strength, compressive strength, cohesive strength, and internal friction angle. By taking the Msalt/Mcement and material ratio as dependent variables, multiple linear regression models of the tensile strength, cohesive strength, and internal friction angle of WCSMPs were established. The interaction law of the Msalt/Mcement and material ratio with the mechanical properties of WCSMPs was obtained. The experimental results showed that the tensile strength, compressive strength, internal friction angle and cohesive strength of the NaCl-WCSMPS were 0.18–0.42 MPa, 1.82–4.57 MPa, 33.1–34.8° and 0.50–1.19 MPa respectively at the curing age of 7d. All the mechanical indexes are in line with the numerical range of submarine hydrate-bearing sediments (HBS).