Drilling Cores and Geophysical Characteristics of Gas Hydrate-Bearing Sediments in the Production Test Region in the Shenhu sea, South China sea

Gas hydrate production testing was conducted in 2017 in the Shenhu Area in the northern part of the South China Sea, and unprecedented success was achieved. In order to obtain gas production and physical properties of gas hydrate reservoirs in the study area and determine the location of test production wells, the seismic and logging data and drilling cores were analyzed in detail, the physical characteristics of the sediments, faults, gas components, and reservoir were studied. The results show that 1) the gas hydrates are diffusion type, with reservoirs dominated by clayey silt sediments, and the gas hydrate-bearing layers are characterized by soup-like, porridge-like, cavity, and vein structures; 2) the resistivity and acoustic velocity of gas hydrate formation are significantly higher than those of the surrounding sediments, while the neutron porosity, density, and natural gamma are slightly lower; the Bottom Simulating Reflectors (BSRs) in seismic profiles exhibit the exist of gas hydrates; 3) gas chimneys and faults are well-developed beneath the BSRs, and hydrocarbon gases can easily migrate into the gas hydrate reservoirs in areas with stable temperature and pressure conditions; 4) the gas hydrate saturation is high, the highest saturation in site W17 was up to 76%, with an average of 33%; while the highest saturation in site W19 was up to 68%, with an average of 31%. The gas source is considered as mixed gas of thermogenic gas and microbial gas. By comparing the core samples and geophysical characteristics of sites W17 and W19 in the study area and calculating the thickness, distribution area, and saturation of the hydrate deposition layer, it was found that site W17 is characterized by a thick layer, large area, high saturation, and good sealing, and thus, site W17 was established as the test production site. The development of gas chimney and faults provides pathways for the upward migration of deep gas, and the gas migrates to gas hydrate stable zone in forms of diffusion, water soluble and free state, forming high saturation of diffusion gas hydrates.

[1]  Wei Zhang,et al.  Quaternary deep-water sedimentary characteristics and their relationship with the gas hydrate accumulations in the Qiongdongnan Basin, Northwest South China Sea , 2021, Deep Sea Research Part I: Oceanographic Research Papers.

[2]  Wei Zhang,et al.  Dynamic accumulation of gas hydrates associated with the channel-levee system in the Shenhu area, northern South China Sea , 2020 .

[3]  Yuanping Li,et al.  Downward shift of gas hydrate stability zone due to seafloor erosion in the eastern Dongsha Island, South China Sea , 2020, Journal of Oceanology and Limnology.

[4]  Wei Zhang,et al.  Geological occurrence and accumulation mechanism of natural gas hydrates in the eastern Qiongdongnan Basin of the South China Sea: Insights from site GMGS5-W9-2018 , 2019 .

[5]  Pushpendra Kumar,et al.  Gas hydrate reservoir identification, delineation, and characterization in the Krishna-Godavari basin using subsurface geologic and geophysical data from the national gas hydrate program 02 expedition, offshore India , 2019, Marine and Petroleum Geology.

[6]  Hailong Lu,et al.  Chemical and structural characteristics of gas hydrates from the Haima cold seeps in the Qiongdongnan Basin of the South China Sea , 2019, Journal of Asian Earth Sciences.

[7]  Jianhua Xu,et al.  Petroleum systems modeling on gas hydrate of the first experimental exploitation region in the Shenhu area, northern South China sea , 2018, Journal of Asian Earth Sciences.

[8]  Jinqiang Liang,et al.  Geomorphological-geological-geophysical signatures of high-flux fluid flows in the eastern Pearl River Mouth Basin and effects on gas hydrate accumulation , 2018, Science China Earth Sciences.

[9]  G. Crutchley,et al.  Gas Hydrate Formation Amid Submarine Canyon Incision: Investigations From New Zealand's Hikurangi Subduction Margin , 2017 .

[10]  Wei Zhang,et al.  Accumulation features and mechanisms of high saturation natural gas hydrate in Shenhu Area, northern South China Sea , 2017 .

[11]  Jinqiang Liang,et al.  Integrated core-log facies analysis and depositional model of the gas hydrate-bearing sediments in the northeastern continental slope, South China Sea , 2017 .

[12]  Jinqiang Liang,et al.  Types, Characteristics and Significances of Migrating Pathways of Gas‐bearing Fluids in the Shenhu Area, Northern Continental Slope of the South China Sea , 2017 .

[13]  Yang Sheng-xiong,et al.  Characteristics of high gas hydrate distribution in the Shenhu area on the northern slope of the South China Sea , 2017 .

[14]  Jinqiang Liang,et al.  Concentrated Gas Hydrate in the Shenhu Area, South China Sea: Results From Drilling Expeditions GMGS3 & GMGS4 , 2017 .

[15]  Praveen Linga,et al.  Review of natural gas hydrates as an energy resource: Prospects and challenges ☆ , 2016 .

[16]  Liang Jinqiang,et al.  Accumulation characteristics and genetic models of natural gas hydrate reservoirs in the NE slope of the South China Sea , 2016 .

[17]  J. Santamarina,et al.  Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough , 2015 .

[18]  M. Lee,et al.  Geological controls on the occurrence of gas hydrate from core, downhole log, and seismic data in the Shenhu area, South China Sea , 2014 .

[19]  Z. Kuang,et al.  Characteristics and occurrence of submarine canyon-associated landslides in the middle of the northern continental slope, South China Sea , 2014 .

[20]  Shunli Li,et al.  Depositional characteristics and accumulation model of gas hydrates in northern South China Sea , 2014 .

[21]  Ji-hoon Kim,et al.  Gas hydrate occurrences and their relation to host sediment properties: Results from Second Ulleung Basin Gas Hydrate Drilling Expedition, East Sea , 2013 .

[22]  T. Lorenson,et al.  The Global Occurrence of Natural Gas Hydrate , 2013 .

[23]  William F. Waite,et al.  Hydrate morphology: Physical properties of sands with patchy hydrate saturation , 2012 .

[24]  M. Lee,et al.  Pore- and fracture-filling gas hydrate reservoirs in the Gulf of Mexico Gas Hydrate Joint Industry Project Leg II Green Canyon 955 H well , 2012 .

[25]  W. Shedd,et al.  Architecture of gas-hydrate-bearing sands from Walker Ridge 313, Green Canyon 955, and Alaminos Canyon 21: Northern deepwater Gulf of Mexico , 2012 .

[26]  R. Davies,et al.  Deepwater canyons: An escape route for methane sealed by methane hydrate , 2012 .

[27]  Tadaaki Shimada,et al.  Particle size effect on the saturation of methane hydrate in sediments – Constrained from experimental results , 2011 .

[28]  U. Shankar,et al.  Documenting channel features associated with gas hydrates in the Krishna–Godavari Basin, offshore India , 2011 .

[29]  Xin Wang,et al.  American Association of Petroleum Geologists Memoir , 2011 .

[30]  Liu Ying-li.  Analysis on Potential Gas Source of Gas Hydrate from the Original Characteristics of Shallow Gas in the North of the South China Sea , 2011 .

[31]  Ayhan Demirbas,et al.  Methane hydrates as potential energy resource: Part 2 – Methane production processes from gas hydrates , 2010 .

[32]  Sun Pi-bo.  Logging Response Characteristics of Gas Hydrate Formation in Shenhu Area of the South China Sea , 2010 .

[33]  Wang Xiu-juan.  Study on Hydrocarbon Leakage System and Associated Gas Hydrate Reservoirs in the Deepwater Basin of Northern South China Sea , 2010 .

[34]  T. S. Collett,et al.  Resource potential of gas hydrates: recent contributions from international research and development projects , 2010 .

[35]  Liang Jin-qiang.  Relationship between the Sonic Logging Velocity and Saturation of Gas Hydrate in Shenhu Area,Northern Slope of South China Sea , 2009 .

[36]  C. Xiao,et al.  Origin of low resistivity reservoirs in low angle drape structure in Lunnan, Tarim Basin , 2008 .

[37]  Liang Jin-qiang.  Well Logging Evaluation of Gas Hydrates in Shenhu Area,South China Sea , 2008 .

[38]  Wang Zhi-feng.  Genetic types of natural gas and characteristic of the gas source composition in marginal basins of the northern South China Sea , 2008 .

[39]  Wang Hong-bin,et al.  PRELIMINARY DISCUSSION ON NATURAL GAS HYDRATE (NGH) RESERVOIR SYSTEM OF SHENHU AREA,NORTH SLOPE OF SOUTH CHINA SEA , 2007 .

[40]  Liu Can-de,et al.  QUANTITATIVE MODELING OF SUSPENDED SEDIMENT IN MIDDLE CHANGJIANG RIVER FROM MODIS , 2006 .

[41]  Shiguo Wu,et al.  Factors affecting the estimation of gas hydrate and free gas saturation , 2006 .

[42]  Jeffery B. Klauda,et al.  Global Distribution of Methane Hydrate in Ocean Sediment , 2005 .

[43]  Liangxu Jin,et al.  Estimation of the Heat Flow in the Northern of the South China Sea Based on the Seismic Data of Gas Hydrate , 2005 .

[44]  Wang Zhu.  LOGGING IDENTIFICATION AND EVALUATION METHODS FOR GAS HYDRATE , 2003 .

[45]  T. Collett.  Energy resource potential of natural gas hydrates , 2002 .

[46]  W. Borowski,et al.  Global and local variations of interstitial sulfate gradients in deep-water, continental margin sediments: Sensitivity to underlying methane and gas hydrates , 1999 .

[47]  J. S. Booth,et al.  Circumstantial Evidence of Gas Hydrate and Slope Failure Associations on the United States Atlantic Continental Margin , 1994 .

[48]  M. Lee,et al.  Method of estimating the amount of in situ gas hydrates in deep marine sediments , 1993 .

[49]  K. Kvenvolden.  Gas hydrates—geological perspective and global change , 1993 .

[50]  Earl E. Davis,et al.  A mechanism for the formation of methane hydrate and seafloor bottom‐simulating reflectors by vertical fluid expulsion , 1992 .

[51]  W. Dillon,et al.  Is the extent of glaciation limited by marine gas-hydrates , 1991 .

[52]  S. Onodera.  Geology and geochemistry , 1971 .