Experimental Study on Sand Removal by a Downhole In Situ Spiral-Swirl Natural Gas Hydrate Coupling Separator

In natural gas hydrate exploitation, the large amount of sand production directly or indirectly leads to the low efficiency of hydrate exploitation and even the termination of exploitation. A spiral-cyclone coupling separator was used to achieve the separation of mud and sand. In this study, based on the actual size of the spiral-cyclone separator for natural gas hydrate, an experimental prototype of the spiral-cyclone separator suitable for indoor experiments was processed, and an indoor experimental system was built. A pressure loss experiment on the hydrate separation device was carried out, and the results proved the correctness of the numerical simulation model of the spiral-swirl separator and the calculation results. The influence of the inlet flow rate of the separator on the separation effect was studied. It was found that with an increase in the flow rate, the mud/sand separation area began to move up, and the mud/sand settlement area at the bottom appeared to have different degrees of mud/sand accumulation. The indoor experimental results and numerical simulation results show that the separation efficiency increases with the flow rate increase in the range of 5–25 m3/h. This study can provide theoretical guidance for the indoor experimental verification of downhole in situ separators.