Main progress of the second gas hydrate trial production in the South China Sea

The natural gas hydrates-bearing shaly silt reservoirs are considered to be the most difficult target in exploitation. The first trial production test of the gas hydrate in the South China Sea conducted in 2017 proved that the reservoir is exploitable. On the basis of the understanding of the previous trial production, optimization and fine description of hydrate deposits, numerical simulation and onshore tests, the second gas hydrate trial production test were carried out by the China Geological Survey in the Shenhu sea area of the South China Sea from October 2019 to April 2020. This trial production overcame a series of technical problems, such as well head stability, horizontal well drilling, reservoir stimulating and sand controlling and accurate depressurizing, and achieved continuous gas production for 30 days, with a total gas output of 861400 cubic meters and a daily average gas production of 28700 cubic meters, which is 5.57 times the first trial production, thus greatly increasing the daily gas production and total gas production. The results show that there existed no abnormal methane content in sea floor, sea water and atmosphere during the whole process. The success of this test shows that it is possible to efficiently and safely develop the gas hydrate in shaly silt reservoirs.