Impact of seafloor drilling on methane seepage—enlightenments from natural gas hydrate drilling site GMGS2-16, northern South China Sea
-
摘要:
目前世界上许多国家对海洋天然气水合物开展了调查和试开采，但是对水合物开发与海底甲烷渗漏之间的关系缺乏了解。本文依托我国第二次天然气水合物钻探航次(GMGS2)，对GMGS2-16钻孔开展了两次钻后甲烷渗漏调查。第一次使用水下机器人(ROV)在该孔开钻之前、钻探过程中及完钻67天内进行了4次海底观察，其中开钻之前未发现海底甲烷渗漏，而在完钻后的两次海底观察中，发现大量气泡从废弃井口冒出。第二次使用船载多波束在该孔完钻18个月后开展水体调查，发现水体中存在火焰状的高回波强度，表明水体中存在气体羽状流，指示海底发生了甲烷渗漏。地震剖面显示该站位水合物赋存层下伏游离气，甲烷渗漏可能是由于钻探打通了海底与该游离气层，形成了甲烷气体运移的优势通道，造成海底甲烷渗漏。多波束水体数据显示甲烷气泡从海底溢出，在海面以下约650m处消失，表明甲烷气体在通过水体的过程中被完全溶解，因此，钻探导致的甲烷渗漏对大气的影响较小。未来随着井壁的坍塌以及水合物在井内的形成，气体运移的优势通道将会完全关闭，甲烷渗漏终止。
Abstract:There are a few countries in the world, which have conducted gas hydrate exploration and test production. However, the knowledge about the impact of seafloor drilling on methane seepage is limited. This study conducted two post seafloor investigations on the GMGS2-16 drilling site of the second gas hydrate drilling expedition (GMGS2). The first investigation consisted of four ROV dives, including one dive before drilling, one dive during drilling and two dives after drilling. The first dive did not find any seafloor gas emission. However, during the last two dives, massive gas bubble emission was observed from the abandoned well. The second investigation was conducted with multibeam echosounder 18 months after the well GMGS2-16A was completed. Flare-shaped high amplitude backscatter was observed in the water column, indicating methane leakage from the seafloor. The seismic profile showed that the free gas was distributed beneath the hydrate-bearing sediment. The seafloor drilling penetrated the hydrate-bearing sediment layer and built up the pathway between seafloor and free gas reservoir, which led to seafloor methane seepage. The water column multibeam data shows that gas flares disappeared at around 650 mbsl, indicating that methane gas was totally dissolved in the seawater. The impact of drilling-induced methane seepage on the atmosphere is quite limited. The methane leakage will stop when the pathways are closed by wall collapse and hydrate deposited later.
-
-
图 5 A:钻探开始前的ROV海底观察；B:钻探结束后刷井眼过程中ROV观察发现有气泡冒出；C和D: 16A完钻60天后的ROV海底观察；E: 16A完钻67天后的ROV海底观察
Figure 5.
图 6 A和B为多波束调查发现的水体羽状流；C为水体羽状流区域(蓝色)与GMGS2-16井位的位置关系，黑线为调查船行驶路线；D为水体多波束与海底地形的三维视图
Figure 6.
-
[1] Sloan Jr E D, Koh C. Clathrate Hydrates of Natural Gases[M]. CRC Press, 2007.
[2] Klauda J B, Sandler S I. Global distribution of methane hydrate in ocean sediment[J]. Energy & Fuels, 2005, 19(2): 459-470.
[3] Milkov A V. Global estimates of hydrate-bound gas in marine sediments: how much is really out there?[J]. Earth-Science Reviews, 2004, 66(3-4): 183-197. doi: 10.1016/j.earscirev.2003.11.002
[4] Lee S Y, Holder G D. Methane Hydrates Potential as a Future Energy Source[M]. Fuel Processing Technology, 2001, 71(1-3): 181-186.
[5] Moridis G J, Collett T S, Boswell R, et al. Gas Hydrates as a Potential Energy Source: State of Knowledge and Challenges, in Advanced Biofuels and Bioproducts[M]. Advanced Biofuels and Bioproducts, Springer, 2013: 977-1033.
[6] Katz M E, Pak D K, Dickens G R, et al. The source and fate of massive carbon input during the latest Paleocene thermal maximum[J]. Science, 1999, 286(5444): 1531-1533. doi: 10.1126/science.286.5444.1531
[7] Maslin M, Mikkelsen N, Vilela C, et al. Sealevel and gashydrate controlled catastrophic sediment failures of the Amazon Fan[J]. Geology, 1998, 26(12): 1107-1110. doi: 10.1130/0091-7613(1998)026<1107:SLAGHC>2.3.CO;2
[8] Dickens G R. Rethinking the global carbon cycle with a large, dynamic and microbially mediated gas hydrate capacitor[J]. Earth and Planetary Science Letters, 2003, 213(3-4): 169-183. doi: 10.1016/S0012-821X(03)00325-X
[9] Klaucke I, Sahling H, Weinrebe W, et al. Acoustic investigation of cold seeps offshore Georgia, eastern Black Sea[J]. Marine Geology, 2006, 231(1-4): 51-67. doi: 10.1016/j.margeo.2006.05.011
[10] Klapp S A, Bohrmann G, Kuhs W F, et al. Microstructures of structure I and II gas hydrates from the Gulf of Mexico[J]. Marine and Petroleum Geology, 2010, 27(1): 116-125. doi: 10.1016/j.marpetgeo.2009.03.004
[11] Wei J, Pape T, Sultan N, et al. Gas hydrate distributions in sediments of pockmarks from the Nigerian margin-Results and interpretation from shallow drilling[J]. Marine and Petroleum Geology, 2015, 59: 359-370. doi: 10.1016/j.marpetgeo.2014.09.013
[12] Bourry C, Chazallon B, Charlou J L, et al. Free gas and gas hydrates from the Sea of Marmara, Turkey: Chemical and structural characterization[J]. Chemical Geology, 2009, 264(1-4): 197-206. doi: 10.1016/j.chemgeo.2009.03.007
[13] Rõmer M, Sahling H, Pape T, et al. Quantification of gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)[J]. Journal of Geophysical Research: Oceans, 2012, 117(C10). http://www.wanfangdata.com.cn/details/detail.do?_type=perio&id=10.1029/2011JC007424
[14] Dewangan P, Sriram G, Ramprasad T, et al. Fault system and thermal regime in the vicinity of site NGHP-01-10, Krishna-Godavari basin, Bay of Bengal[J]. Marine and Petroleum Geology, 2011, 28(10): 1899-1914. doi: 10.1016/j.marpetgeo.2011.03.009
[15] Kim G Y, Yi B Y, Yoo D G, et al. Evidence of gas hydrate from downhole logging data in the Ulleung Basin, East Sea[J]. Marine and Petroleum Geology, 2011, 28(10): 1979-1985. doi: 10.1016/j.marpetgeo.2011.01.011
[16] Yang S, Liang J, Lei Y, et al. GMGS4 gas hydrate drilling expedition in the South China Sea[J]. Fire In The Ice, 2017, 17(1): 7-11.
[17] EIA U. Annual energy outlook 2013[J]. US Energy Information Administration, Washington, DC, 2013: 60-62. http://d.old.wanfangdata.com.cn/Periodical/syqc201401043
[18] Riedel M, Collett T, Shankar U. Documenting channel features associated with gas hydrates in the Krishna-Godavari Basin, offshore India[J]. Marine Geology, 2011, 279(1-4): 1-11. doi: 10.1016/j.margeo.2010.10.008
[19] Li X S, Xu C G, Zhang Y, et al. Investigation into gas production from natural gas hydrate: A review[J]. Applied Energy, 2016, 172: 286-322. doi: 10.1016/j.apenergy.2016.03.101
[20] Kim J H, Torres M E, Hong W L, et al. Pore fluid chemistry from the Second Gas Hydrate Drilling Expedition in the Ulleung Basin (UBGH2): Source, mechanisms and consequences of fluid freshening in the central part of the Ulleung Basin, East Sea[J]. Marine and Petroleum Geology, 2013, 47: 99-112. doi: 10.1016/j.marpetgeo.2012.12.011
[21] Horozal S, Kim G Y, Bahk J J, et al. Core and sediment physical property correlation of the second Ulleung Basin Gas Hydrate Drilling Expedition (UBGH2) results in the East Sea (Japan Sea)[J]. Marine and Petroleum Geology, 2015, 59: 535-562. doi: 10.1016/j.marpetgeo.2014.09.019
[22] Yamamoto K. Overview and introduction: Pressure core-sampling and analyses in the 2012-2013 MH21 offshore test of gas production from methane hydrates in the eastern Nankai Trough[J]. Marine and Petroleum Geology, 2015, 66: 296-309. doi: 10.1016/j.marpetgeo.2015.02.024
[23] Leifer I, Solomon E, von Deimling J S, et al. The fate of bubbles in a large, intense bubble megaplume for stratified and unstratified water: Numerical simulations of 22/4b expedition field data[J]. Marine and Petroleum Geology, 2015, 68: 806-823. doi: 10.1016/j.marpetgeo.2015.07.025
[24] Judd A. The significance of the 22/4b blow-out site methane emissions in the context of the North Sea[J]. Marine and Petroleum Geology, 2015, 68: 836-847. doi: 10.1016/j.marpetgeo.2015.07.031
[25] Vielstädte L, Karstens J, Haeckel M, et al. Quantification of methane emissions at abandoned gas wells in the Central North Sea[J]. Marine and Petroleum Geology, 2015, 68: 848-860. doi: 10.1016/j.marpetgeo.2015.07.030
[26] Wiggins S M, Leifer I, Linke P, et al. Long-term acoustic monitoring at North Sea well site 22/4b[J]. Marine and Petroleum Geology, 2015, 68: 776-788. doi: 10.1016/j.marpetgeo.2015.02.011
[27] Sha Z, Liang J, Zhang G, et al. A seepage gas hydrate system in northern South China Sea: Seismic and well log interpretations[J]. Marine Geology, 2015, 366: 69-78. doi: 10.1016/j.margeo.2015.04.006
[28] Zhang G, Liang J, Lu J A, et al. Geological features, controlling factors and potential prospects of the gas hydrate occurrence in the east part of the Pearl River Mouth Basin, South China Sea[J]. Marine and Petroleum Geology, 2015, 67: 356-367. doi: 10.1016/j.marpetgeo.2015.05.021
[29] Sultan N, Bohrmann G, Ruffine L, et al. Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution[J]. Journal of Geophysical Research: Solid Earth, 2014, 119(4): 2679-2694. doi: 10.1002/2013JB010546
[30] Bohrmann G, Torres M E.Gas Hydrates in Marine Sediments, in Marine Geochemistry[M]. Springer, 2006: 481-512.
[31] Torres M, Wallmann K, Tréhu A, et al. Gas hydrate growth, methane transport, and chloride enrichment at the southern summit of Hydrate Ridge, Cascadia margin off Oregon[J]. Earth and Planetary Science Letters, 2004, 226(1-2): 225-241. doi: 10.1016/j.epsl.2004.07.029
[32] McGinnis D F, Greinert J, Artemov Y, et al. Fate of rising methane bubbles in stratified waters: How much methane reaches the atmosphere?[J]. Journal of Geophysical Research: Oceans, 2006, 111(C9). http://d.old.wanfangdata.com.cn/NSTLQK/10.1029-2005JC003183/
[33] Rehder G, Brewer P W, Peltzer E T, et al. Enhanced lifetime of methane bubble streams within the deep ocean[J]. Geophysical Research Letters, 2002, 29(15): 21-1-21-4. doi: 10.1029/2001GL013966
-
下载:
图(7)
计量
- 文章访问数: 1679
- PDF下载数: 22
- 施引文献: 0