China Geology

ABSTRACT Natural gas hydrates (NGH) is one of key future clean energy resources. Its industrialized development will help remit the huge demand of global natural gas, relieve the increasing pressure of the environment, and play a vital role in the green sustainable growth of human societies. Based on nearly two decades’ studying on the reservoir characteristics in the South China Sea (SCS) and the knowledge of reservoir system, the China Geological Survey (CGS) conducted the first production test on an optimal target selected in Shenhu area SCS in 2017. Guided by the “three-phase control” exploitation theory which focused on formation stabilization, technologies such as formation fluid extraction, well drilling and completing, reservoir stimulating, sand controlling, environmental monitoring, monitoring and preventing of secondary formation of hydrates were applied. The test lasted for 60 days from May 10th when starting to pump, drop pressure and ignite to well killing on July 9th, with gas production of 3.09×105 m3 in total, which is a world record with the longest continuous duration of gas production and maximal gas yield. This successful test brings a significant breakthrough on safety control of NGH production.

Jin-fa Li

China Geological Survey Beijing 100037 China

Jian-liang Ye

Xu-wen Qin

Hai-jun Qiu

Neng-you Wu

Hai-long Lu

Wen-wei Xie

Jing-an Lu

Fei Peng

Zhen-qiang Xu

Cheng Lu

Zeng-gui Kuang

Jian-gong Wei

Qian-yong Liang

Hong-feng Lu

Bei-bei Kou

Guangzhou Marine Geological Survey China Geological Survey Guangzhou 510075 China

Qingdao Institute of Marine Geology China Geological Survey Qingdao 266071 China

Peking University Beijing 100871 China

Institute of Exploration Techniques China Academy of Geological Sciences Langfang 065000 China

CNPC Offshore Engineering Company Ltd. Beijing 100102 China

Center of Oil &amp; Natural Gas Resource Exploration China Geological Survey Beijing 100083 China

The first offshore natural gas hydrate production test in South China Sea

南海首次海域天然气水合物试采

ABSTRACT 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 ×104 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.

China Geological Survey Ministry of Natural Resources Beijing 100037 China

Bao-jin Ma

Jin-qiang Liang

Shi-peng Wei

Yan-jiang Yu

Chun-sheng Liu

Bin Li

Kai-xiang Shen

Hao-xian Shi

Qiu-ping Lu

Jing Li

Gang Song

Bo Li

He-en Zhang

Chao Ma

Yi-fei Dong

Hang Bian

Guangzhou Marine Geological Survey China Geological Survey Ministry of Natural Resources Guangzhou 510075 China

Institute of Exploration Techniques China Geological Survey Ministry of Natural Resources Langfang 065000 China

CNPC Offshore Engineering Company Limited Beijing 100102 China

Oil and Gas Resources Survey China Geological Survey Ministry of Natural Resources Beijing 100083 China

Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) Guangzhou 510000 China

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

南海第二次天然气水合物试采

To study the current status and causes of the microplastic pollution in surface water of the Qinghai-Tibet Plateau, this paper compared the average microplastic abundance in sediments and surface water of the Qinghai-Tibet Plateau and the results are as follows. First, the average microplastic abundance in surface water of the independent rivers and the whole area is 247−2686 items/m3 and 856 items/m3, respectively. The average microplastic abundance in sediments of independent rivers or lakes and the whole area is 0−933 items/m2 and 362 items/m2, respectively. Meanwhile, the degree of microplastic pollution in river sediments is higher than that in lake sediments, and the rivers suffering from microplastic pollution mainly include the Brahmaputra River, Tongtian River, and Nujiang River. Second, compared with the microplastic pollution in other areas of the world, the levelof microplastic pollution in the lakes and rivers of the Qinghai-Tibet plateau is not lower than that of well-developed areas with more intensive human activities. Finally, this study suggests that relevant government departments of the Qinghai-Tibet Plateau should strengthen waste management strategies while developing tourism and that much attention should be paid to the impacts of microplastics in the water environment.

Rui-ping Liu

Ying Dong

Guo-cang Quan

Hua Zhu

You-ning Xu

Rafaey M Elwardany

Microplastic pollution in surface water and sediments of Qinghai-Tibet Plateau: Current status and causes

青藏高原地表水及沉积物中的微塑料污染：现状与成因

Renat Shakirov

Vladimir Luchin

Evgeniya Petrova

Nengyou Wu

Yizhao Wan

Spatial and temporal variations in parameters at the upper boundary of gas hydrate stability zone of the Sea of Okhotsk

鄂霍次克海天然气水合物稳定带顶界参数的时空变化

Zong-yue Lu

Gen-yuan Liu

Xi-dong Zhao

Kang Sun

Yan-si Chen

Zhi-hong Song

Kai Xue

Ming-shan Yang

Landslide susceptibility assessment based on an interpretable coupled FR-RF model: A case study of Longyan City, Fujiang province, Southeast China

基于可解释耦合FR-RF模型的滑坡易发性评估：以中国东南部福建省龙岩市为例

Rui-chen Chen

Jian Chen

Sheng Ma

Zi-ang Yan

Qian Shi

A novel model for predicting rock avalanche runout using source area width from 63 representative cases

利用63个代表性案例的源区宽度预测岩崩运动距离的新模型

Zhi-qiang Wu

Hai-ying Li

Liu-yan Lü

Guo-jun Liang

Ting-ting Wu

Jiang-xia Zhu

Distributions and risk assessment of heavy metals in solid waste in lead-zinc mining areas and across the soil water body sediment agricultural product ecosystem in their surrounding areas

铅锌矿区固体废物中重金属的分布及风险评估及其周边土壤-水体-沉积物-农产品生态系统中的分布与风险评估

De-gen Zhu

Jing Ning

Hui Yang

Jun-bing Pu

Jian-hua Cao

Meng-xia Zhou

Mitja Prelovšek

Nataša Ravbar

Research hotspot and trend of plant water use in karst: Based on a bibliometric analysis from 1984 to 2022

喀斯特植物水分利用的研究热点与趋势：基于1984年至2022年的文献计量分析

Abbreviation	zgdzyw
Journal Impact	4.64
Quartiles(Global)	GEOSCIENCES, MULTIDISCIPLINARY(Q1)

ISSN	2096-5192, 2589-9430
h-index	23

Publication Information	Publisher: KeAi Communications Co.，Publishing cycle: ，Journal Type: journal，Open Access Journals: Yes
Basic data	Year of publication: 2018，Proportion of original research papers: 85.71%，Self Citation Rate:4.30%， Gold OA Rate: 94.67%
Average review cycle	网友分享经验：16 Weeks

China Geology

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The first offshore natural gas hydrate production test in South China Sea

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

Microplastic pollution in surface water and sediments of Qinghai-Tibet Plateau: Current status and causes

Spatial and temporal variations in parameters at the upper boundary of gas hydrate stability zone of the Sea of Okhotsk

Landslide susceptibility assessment based on an interpretable coupled FR-RF model: A case study of Longyan City, Fujiang province, Southeast China

Spatial and temporal variations in parameters at the upper boundary of gas hydrate stability zone of the Sea of Okhotsk

Landslide susceptibility assessment based on an interpretable coupled FR-RF model: A case study of Longyan City, Fujiang province, Southeast China

A novel model for predicting rock avalanche runout using source area width from 63 representative cases

Distributions and risk assessment of heavy metals in solid waste in lead-zinc mining areas and across the soil water body sediment agricultural product ecosystem in their surrounding areas

Research hotspot and trend of plant water use in karst: Based on a bibliometric analysis from 1984 to 2022