Evaluation of Frictional Properties for Methane-Hydrate-Well Completion and Production

Summary During methane-hydrate production in offshore deepwater seabeds, there are concerns about the settlement of the seabed and the possibility that negative friction will occur along the production well. However, frictional properties of a deepwater well structure are not investigated. Here, friction tests were conducted on interfacial boundaries among a steel rod and sand and a steel rod and cement under high confining pressure. Three types of steel rods with different surface roughness, two types of silica sand with different particle sizes, and cement were used. A steel rod confined by compacted sand or hardened cement was pushed out at a constant displacement rate. The tests show that frictional strength of two kinds of interfacial boundaries increased linearly with confining pressure. In addition, the results confirmed the effective friction angle of the interface between a steel rod and sand and the cohesion of the interface between the steel rod and cement increases with the surface roughness of the steel rod.