The second natural gas hydrate production test in the South China Sea

• 作者: Bao-jin Ma Bei-bei Kou Bin Li Bo Li Chao Ma Cheng Lu Chun-sheng Liu Gang Song Hai-jun Qiu Hai-long Lu Hang Bian Hao-xian Shi He-en Zhang Hong-feng Lu Jian-liang Ye Jin-qiang Liang Jing Li Jing-an Lu Kai-xiang Shen Qian-yong Liang Qiu-ping Lu Shi-peng Wei Wen-wei Xie Xu-wen Qin Yan-jiang Yu Yi-fei Dong Zeng-gui Kuang
• 来源期刊: 中国地质（英文）
• 关键词: Natural gas hydrates Second production test Horizontal well Reservoir stimulation Environmental impact NGH exploration trial engineering South China Sea
• 年，卷（期）: 2020,（2）
• 页码范围: 197-209
• 页数: 13页
• 语种: 中文
• DOI: 10.31035/cg2020043

摘要

Clayey silt reservoirs bearing natural gas hydrates (NGH) are considered to be the hydrate-bearing reservoirs that boast the highest reserves but tend to be the most difficult to exploit.They are proved to be exploitable by the first NGH production test conducted in the South China Sea in 2017.Based on the understanding of the first production test,the China Geological Survey determined the optimal target NGH reservoirs for production test and conducted a detailed assessment,numerical and experimental simulation,and onshore testing of the reservoirs.After that,it conducted the second offshore NGH production test in 1225 m deep Shenhu Area,South China Sea (also referred to as the second production test) from October 2019 to April 2020.During the second production test,a series of technical challenges of drilling horizontal wells in shallow soft strata in deep sea were met,including wellhead stability,directional drilling of a horizontal well,reservoir stimulation and sand control,and accurate depressurization.As a result,30 days of continuous gas production was achieved,with a cumulative gas production of 86.14 ×l04 m3.Thus,the average daily gas production is 2.87 ×104 m3,which is 5.57 times as much as that obtained in the first production test.Therefore,both the cumulative gas production and the daily gas production were highly improved compared to the first production test.As indicated by the monitoring results of the second production test,there was no anomaly in methane content in the seafloor,seawater,and atmosphere throughout the whole production test.This successful production test further indicates that safe and effective NGH exploitation is feasible in clayey silt NGH reservoirs.The industrialization of hydrates consists of five stages in general,namely theoretical research and simulation experiments,exploratory production test,experimental production test,productive production test,and commercial production.The second production test serves as an important step from the exploratory production test to experimental production test.