Size selection of the sand-control gravel particle in the argillaceous siltstone reservoirs of natural gas hydrate in sea areas

In May 2017, production test of natural gas hydrate in sea areas succeeded in China, and breakthrough achievements were also obtained in the key sand control technologies. The argillaceous siltstone reservoirs with the characteristics of weak consolidation, high fine particle content and high sand control difficulty coefficient were taken as the research object. After domestic and foreign key sand control technologies for the production test of natural gas hydrate were analyzed, combined with the particle size distribution range of the production tested reservoir and the mixing characteristics of packing gravels in the sea area of the South China Sea, the equivalent pore size model of mixed particle size combination was established. The pore distribution range of gravel buildups with mixed particle size of some industrial gravel was calculated and then converted into the sand-retention particle size. Based on the theoretical analysis, the physical model experiment was designed to carry out the sand retention experiments on the simulated reservoir with different gravel particle sizes. It is verified that the gravel of 0.23−0.32 mm can prevent massive sand production of argillaceous siltstone reservoirs below 0.04 mm. The research results provide the theoretical basis for the selection of sand control gravel size in natural gas hydrate production test in China.