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1.
分析了琼东南盆地华光凹陷天然气水合物稳定条件、气源供给来源、运移通道类型等成藏条件,指出了研究区天然气水合物的勘探方向并建立了天然气水合物的成藏模式。华光凹陷浅部沉积层的温度、压力条件满足天然气水合物形成的要求,生物成因甲烷水合物稳定带最大厚度约320m,热成因天然气水合物稳定带最大厚度约为345m。气源岩主要分布在凹陷西部地区的断陷期层序中,具有早、晚两期生烃且以晚期为主的特征,有利于热解成因气在水合物稳定带内的聚集成藏。晚中新世以来快速沉降的巨厚半深海细粒沉积物为生物成因气的形成提供了物质基础。泥底辟与其伴生断裂及多边形断层等构成了天然气水合物成藏的主要流体运移体系。华光凹陷靠近(1)号断裂的西部地区是有利的勘探方向。晚中新世以来的快速沉降使得渐新世成熟—过熟烃源岩大量生气或裂解,而且由于欠压实作用形成的地层超压为含气流体的运移提供了强大的动力。热解天然气和生物气沿着泥底辟和多边形断层等构成的输导网络向上垂向运移至水合物稳定带,形成天然气水合物,其中深水浊流水道是寻找高饱和度水合物的有利目标体。 相似文献
2.
《海洋地质前沿》2021,(7)
琼东南盆地深水区天然气水合物富集条件优越,具有巨大的勘探开发前景。基于近年来新获取的海洋地质地球物理关键参数,反演了琼东南盆地深水区上新世(约5 Ma)以来的天然气水合物稳定域迁移过程。研究表明:琼东南盆地现今天然气水合物稳定域主要存在于水深600 m的海底,约在水深1 800~2 400 m处水合物稳定域厚度达到最大值,约190 m;冰期海平面下降导致水合物稳定域向深海平原迁移,而陆坡-深海平原转换带的水合物稳定域厚度则相对于现今减薄约80 m;岩浆热事件导致深海平原水合物稳定域厚度减薄约50 m,天然气水合物随之分解后释放大量气体导致多边形断层形成。 相似文献
3.
《海洋地质与第四纪地质》2021,(2)
利用基于热力学理论的CSMHYD程序,模拟预测了末次冰期以来南海东沙海域深水区天然气水合物稳定带(GHSZ)的演化特征,同时讨论了海平面、底水温度对该区天然气水合物稳定带变化的影响,以及水合物分解对环境的影响。结果表明:(1)水深超过595 m的海域具备形成天然气水合物的环境条件;GHSZ平均厚度可达245 m,其中最厚区位于研究区东部,超过380 m,其次为东沙陆坡段与台湾浅滩陆坡段的结合部。(2)末次冰期(LGM)以来东沙海域GHSZ厚度呈现不对称旋回变化,按照时间由老到新可以分为TC1、TC2、TC3、TC4和TC5共5个完整的旋回。稳定带变化的减薄半旋回持续时间要长于增厚半旋回。TC1—TC4旋回内GHSZ厚度变化受海平面升降的控制,TC5旋回内稳定带厚度变化受到海底温度的控制。(3)在由陆缘向中央海盆方向逐渐增大的高地温梯度背景下,LGM以来海底温度和海平面变化对GHSZ的影响在中层水范围内大于深层水;同时水柱引起的压力效应在中层水深度范围内相对较大,深层水范围内海平面变化对GHSZ的影响十分有限。东沙海域CaCO3含量异常降低可能受水合物分解释放的甲烷气进入水体后引起海水酸化的影响。 相似文献
4.
珠江口和琼东南盆地天然气水合物形成和稳定分布的地球化学边界条件及其分布区 总被引：22，自引：0，他引：22
通过对南海北部陆缘珠江口和琼东南盆地气田的天然气形成水合物的地球化学计算模拟及地质地球化学条件分析，对珠江口和琼东南盆地天然气形成水合物的地球化学边界条件及分布区进行了研究。认识到南海北部陆缘琼东南和珠江口盆地内的断裂构造是天然气向海底渗漏的通道，为天然气水合物在海底的形成提供了物源；盆地内巨厚的第四纪富有机质沉积也为天然气水合物形成提供了充足的细菌成因生物气源。在海底温度2－16℃范围内，琼东南盆地气田10种天然气和珠江口盆地气田18种天然气形成水合物的压力有比较大的范围，随温度增高，天然气水合物形成的压力增高；盆地间和各天然气样品之间形成水合物的压力均是不一致的。在南海海水平均盐度3．4％条件下，结合海底温度与水深变化资料，珠江口和琼东南盆地天然气水合物形成和稳定分布的海区是不同的，珠江口盆地小于230m水深的海区没有天然气水合物的形成，在230－760m水深的海区可能有天然气水合物的存在，天然气水合物的稳定分布区应该在大于860m水深的深水区；在琼东南盆地水深小于320m的海区不可能有天然气水合物的形成，在320－650m水深的海区可能有天然气水合物的存在，大于650m水深的海区是天然气水合物的稳定分布区。 相似文献
5.
6.
南沙海域天然气水合物地震特征 总被引：5，自引：1，他引：5
南沙海域水深为200∽2500m，其中大于500m的水域约50万km^2，该区大部分区域发育沉积盆地，构造类型多样，具有形成天然气水合物的气源、温度及压力条件。根据地质及地球物理调查资料，分析了南沙海域天然气水合物成藏的地质条件及地球物理标志特征，认为南沙海域具备形成天然气水合物矿藏的条件，南沙海槽和南沙中部海域是天然气水合物形成的有利地区。 相似文献
7.
GIS辅助估算南海南部天然气水合物资源量 总被引：10，自引：0，他引：10
具有低温高压条件的深海是天然气水合物形成的有利场所。从海底天然气水合物稳定分布的赋成条件入手,分别根据Levitus水温数据和Sloan的CSMHYD程序拟合出水温水深方程和相界线方程。假定南海南部温度梯度范围为59—90℃·km-1,得天然气水合物稳定带厚度与水深的关系方程。采用最新的南海南部海底数字地形图数据,在GIS平台上分析得到天然气水合物稳定带的分布图,进而获得南海南部天然气水合物稳定带最大厚度为230—355m,容积为5.7×1013—9.5×1013m3;甲烷量为2.451×1015—4.085×1015m3;资源量为1.729×1013—2.169×1013m3。 相似文献
8.
海底天然气水合物稳定带的特征分析 总被引：14，自引：1，他引：14
水合物稳定带（HSZ）控制着海底天然气水合物的成矿作用和分布规律，其厚度及分布范围决定了天然气水合物的蕴藏量，所以水合物稳定带的分析对天然气水合物的成矿与分布规律、成因与演化机制以及资源研究具有重要的指导意义。水合物稳定带本身受海底温度、压力和甲烷量等因素的影响，其变化会影响水合物稳定带的范围、稳定带底界的位置，并制约着天然气水合物的稳定性和甲烷气的释放。 相似文献
9.
东海天然气水合物的区域地质特征及可能的远景区 总被引：7，自引：1，他引：7
从水深、沉积物厚度、沉积速率、有机质含量、地形和地貌来看，冲绳海槽盆地具有天然气水合物形成的区域地质条件，水合物出现的水深在500m以上，冲绳海槽南段水合物潜力最大。与智利三联点相类比，该区水合物可能主要分布在陆坡中部浅地层中。从冲绳海槽盆地的海底温度、海底热流和折射地震层速度资料的分析来看，该区具有水合物稳定存在的温压条件，其中南段和北段的稳定带厚度比中段更大一些，从已解释的穿越冲绳海槽盆地的地震剖面来看，有BSR迹象的剖面段约有300km，主要分布在中段的南部，从底水甲烷和卫星热红外异常分析来看，冲绳海槽盆地南段海域因存在经常性的卫星热红外增温异常和高值底水甲烷异常，因而水合物成藏的条件可能最好。 相似文献
10.
南海北部陆坡区是中国最具潜力的天然气水合物聚集区。通过对研究区似海底反射层（BSR）、水深及热流值分布进行交会,得到了水深、热流双因素对天然气水合物形成的共同控制机理。研究认为,热流值中等（70～83mW／m^2）的地区最有利于天然气水合物的形成和聚集,热流值升高,天然气水合物形成的水深有总体增大的趋势。另外,天然气水合物的形成也需要良好的盖层条件。模拟了当上覆泥质沉积物盖层厚度不同时,天然气水合物形成所需的最低水深,并对不同泥质沉积物盖层厚度对天然气水合物稳定带底界面和厚度的影响做了研究和探讨。当泥质沉积物盖层的厚度越大时,天然气水合物形成的水深可以更浅;当泥质沉积物盖层厚度较小时,天然气水合物的形成则需要更大的水深。另外,当水深越大时,天然气水合物稳定带的底界面（BGHSZ）越深,天然气水合物稳定带的厚度越大。 相似文献
11.
南海北部大陆边缘天然气水合物稳定带厚度的地热学研究 总被引：1，自引：1，他引：0
The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide,given the shortage of fossil fuels.As a potential energy resource,gas hydrate exists only in the environment of high pressure and low temperature,mainly distributing in the sediments of the seafloor in the continental margins and the permafrost zones in land.The accurate determination of the thickness of gas hydrate stability zone is essential yet challenging in the assessment of the exploitation potential.The majority of previous studies obtain this thickness by detecting the bottom simulating reflectors(BSRs) layer on the seismic profiles.The phase equilibrium between gas hydrate stable state with its temperature and pressure provides an opportunity to derive the thickness with the geothermal method.Based on the latest geothermal dataset,we calculated the thickness of the gas hydrate stability zone(GHSZ) in the north continental margin of the South China Sea.Our results indicate that the thicknesses of gas hydrate stability zone vary greatly in different areas of the northern margin of the South China Sea.The thickness mainly concentrates on 200–300 m and distributes in the southwestern and eastern areas with belt-like shape.We further confirmed a certain relationship between the GHSZ thickness and factors such as heat flow and water depth.The thickness of gas hydrate stability zone is found to be large where the heat flow is relatively low.The GHSZ thickness increases with the increase of the water depth,but it tends to stay steady when the water depth deeper than 3 000 m.The findings would improve the assessment of gas hydrate resource potential in the South China Sea. 相似文献
12.
S. Chand J. Mienert K. Andreassen J. Knies L. Plassen B. Fotland 《Marine and Petroleum Geology》2008,25(7):625-636
The Barents Sea seabed exhibits an area of major glacial erosion exposing parts of the old hydrocarbon basins. In this region, we modelled the gas hydrate stability field in a 3D perspective, including the effects of higher order hydrocarbon gases. We used 3D seismic data to analyse the linkage between fluid-flow expressions and hydrate occurrences above old sedimentary basin systems and vertical faults. Pockmarks showed a relation to fault systems where some of them are directly connected to hydrocarbon bearing sedimentary formations. The influence of bottom water temperature, pore water salinity and geothermal gradient variation on gas hydrate stability zone (GHSZ) thickness is critically analysed in relation to both geological formations and salt tectonics. Our analysis suggests a highly variable GHSZ in the Barents Sea region controlled by local variations in the parameters of stability conditions. Recovery of gas-hydrate sample from the region and presence of gas-enhanced reflections below estimated BSR depths may indicate a prevalent gas-hydrate stable condition. 相似文献
13.
珠江口盆地神狐海域是天然气水合物钻探和试验开采的重点区域,大量钻探取心、测井与地震等综合分析表明不同站位水合物的饱和度、厚度与气源条件存在差异。本文利用天然气水合物调查及深水油气勘探所采集的测井和地震资料建立地质模型,利用PetroMod软件模拟地层的温度场、有机质成熟度、烃源岩生烃量、流体运移路径以及不同烃源岩影响下的水合物饱和度,结果表明:生物成因气分布在海底以下1500 m范围内的有机质未成熟地层,而热成因气分布在深度超过2300 m的成熟、过成熟地层。水合物稳定带内生烃量难以形成水合物,形成水合物气源主要来自于稳定带下方向上运移的生物与热成因气。模拟结果与测井结果对比分析表明,稳定带下部生物成因气能形成的水合物饱和度约为10%,在峡谷脊部的局部区域饱和度较高;相对高饱和度(>40%)水合物形成与文昌组、恩平组的热成因气沿断裂、气烟囱等流体运移通道幕式释放密切相关,W19井形成较高饱和度水合物的甲烷气体中热成因气占比达80%,W17井热成因气占比为73%,而SH2井主要以生物成因为主,因此,不同站位甲烷气体来源占比不同。 相似文献
14.
An analysis of 3D seismic data from the northwestern part of the Ulleung Basin, East Sea, revealed that the gas hydrate stability zone (GHSZ) consists of five seismic units separated by regional reflectors. An anticline is present that documents activity of many faults. The seismic indicators of gas hydrate occurrence included bottom simulating reflector (BSR) and acoustic blanking in the gas hydrate occurrence zone (GHOZ). By the analysis of the seismic characteristics and the gradient of the sedimentary strata, the GHOZ was divided into four classes: (1) dipping strata upon strong BSR, (2) dipping strata below strong BSR, (3) parallel strata with acoustic blanking, and (4) parallel strata below weak BSR. Seismic attributes such as reflection strength and instantaneous frequency were computed along the GHOZ. Low reflection strength and high instantaneous frequency were identified above the BSR, indicating the occurrence of gas hydrate. A remarkably high reflection strength and low instantaneous frequency indicated the presence of free gas below the BSR. Considering the distribution of the gas hydrate and free gas, two gas migration processes are suggested: (1) stratigraphic migration through the dipping, permeable strata and (2) structural migration from below the GHSZ along faults. 相似文献
15.
The present paper focuses on heat and mass exchange processes in methane hydrate fragments during in situ displacement from the gas hydrate stability zone (GHSZ) to the water surface of Lake Baikal. After being extracted from the methane hydrate deposit at the lakebed, hydrate fragments were placed into a container with transparent walls and a bottom grid. There were no changes in the hydrate fragments during ascent within the GHSZ. The water temperature in the container remained the same as that of the ambient water (~3.5 °С). However, as soon as the container crossed the upper border of the GHSZ, first signs of hydrate decomposition and transformation into free methane gas were observed. The gas filled the container and displaced water from it. At 300 m depth, the upper and lower thermometers in the container simultaneously recorded noticeable decreases of temperature. The temperature in the upper part of the container decreased to –0.25 °С at about 200 m depth, after which the temperature remained constant until the water surface was reached. The temperature at the bottom of the container reached –0.25 °С at about 100 m depth, after which it did not vary during further ascent. These observed effects could be explained by the formation of a gas phase in the container and an ice layer on the hydrate surface caused by heat consumption during hydrate decomposition (self-preservation effect). However, steady-state simulations suggest that the forming ice layer is too thin to sustain the hydrate internal pressure required to protect the hydrate from decomposition. Thus, the mechanism of self-preservation remains unclear. 相似文献
16.
南海晚新生代构造运动与天然气水合物资源 总被引：6，自引：0，他引：6
南海在新生代经历过两次海底扩张产生了南海洋盆.南海北部和南部原来都是被动大陆边缘,但北部在晚新生代由于菲律宾海板块与欧亚板块在台湾地区发生了碰撞,使陆缘遭受到北西向挤压,在陆缘上产生了北西向左旋走滑活动,我们命名此次构造活动为东沙运动;南部陆缘在早中新世末由于南移的南沙地块与婆罗洲地块发生了碰撞,加上此时北移的菲律宾海板块在明都洛岛地区与欧亚板块发生碰撞,以及南部的东南苏拉威西地块与西北苏拉威西地块发生碰撞,在南海南部产生了挤压构造,我们命名此次构造运动为南沙运动.这两次新生代的构造运动改变了南北陆缘的性质,北部陆缘有人因此称之为准被动陆缘,而南部陆缘的南部则变成了挤压边缘.南海南北陆缘在晚新生代受到的挤压活动,对油气成藏和天然气水合物的形成有重要的推动作用,因为挤压活动有利于流体的流动,进而在适当的地方形成油气藏和天然气水合物. 相似文献
17.
Bin Wang Fuliang Lü Shuang Li Jian Li Zhili Yang Li Li Xuefeng Wang Yintao Lu Taotao Yang Jingwu Wu Guozhong Sun Hongxia Ma Xiaoyong Xu 《海洋学报(英文版)》2021,40(2):29-41
High-resolution multichannel seismic data enables the discovery of a previous, undocumented submarine canyon(Huaguang Canyon) in the Qiongdongnan Basin, northwestern South China Sea. The Huaguang Canyon with a NW orientation is 140 km in length, and 2.5 km to 5 km in width in its upper reach and 4.6 km to 9.5 km in width in its lower reach. The head of the Huaguang Canyon is close to the Xisha carbonate platform and its tail is adjacent to the Central Canyon. This buried submarine canyon is formed by gravity flows from the Xisha carbonate platform when the sea level dropped in the early stage of the late Miocene(around 10.5 Ma). The internal architecture of the Huaguang Canyon is mainly characterized by high amplitude reflections, indicating that this ancient submarine canyon was filled with coarse-grained sediments. The sediment was principally scourced from the Xisha carbonate platform. In contrast to other buried large-scale submarine canyons(Central Canyon and Zhongjian Canyon) in the Qiongdongnan Basin, the Huaguang Canyon displays later formation time,smaller width and length, and single sediment supply. The coarse-grained deposits within the Huaguang Canyon provide a good environment for reserving oil and gas, and the muddy fillings in the Huaguang Canyon have been identified as regional caps. Therefore, the Huaguang Canyon is a potential area for future hydrocarbon exploration in the northwestern South China Sea. The result of this paper may contribute to a better understanding of the evolution of submarine canyons formed in carbonate environment. 相似文献
18.
Preliminary studies of Caspian Sea have shown the possibility of gas hydrate accumulations, because of suitable physicochemical conditions, existence of clayey deposits, and high concentrations of organic matter. Studies have indicated that gas hydrates are mainly composed of methane. Therefore, based on physicochemical equations for methane hydrate stability in different pressure, temperature, and salinity, this study was designed to calculate the potential of gas hydrate formation in the Caspian Sea basin. For this, data of more than 600 locations were analyzed and in each location, upper and lower limits of methane hydrate formation zone were calculated. Then, the zoning maps of upper and lower limits were prepared which can be useful for exploring the gas hydrate as an energy source or predicting gas hydrate hazards. According to the calculations and maps, methane hydrate formation in Caspian Sea, theoretically, can take place from near the seabed to 4000 and 2500 m beneath the sea surface when low and high geothermal gradient are supposed, respectively. By comparing the results with gas hydrate zones revealed in geophysical profiles, it has been shown that, in Caspian Sea, gas hydrates probably accumulate near the lower limit when a high geothermal gradient is assumed. 相似文献
19.
大量研究表明南海北部珠江口盆地是天然气水合物发育区,但是该盆地东部揭阳凹陷水合物研究较少。本文利用揭阳凹陷新采集三维地震资料,对该三维地震资料进行成像道集优化和叠前时间偏移处理,得到针对水合物的新处理地震数据体,并通过高精度网格层析反演得到层速度数据体。利用该数据开展叠后约束稀疏脉冲反演,获得含天然气水合物地层波阻抗异常,综合分析反演与地震属性识别水合物。从新处理地震资料看,该区域似海底反射(bottom simulation reflection,BSR)反射呈连续、不连续与地层斜交等特征,BSR发育在一个继承性小型水道上,且下部断裂和气烟囱发育。通过分析BSR特征及BSR上下地层的速度、波阻抗、振幅、频率、相干等属性异常,结合水合物成藏条件,发现了南海北部新的天然气水合物有利富集区,为该区域水合物勘探提供基础。 相似文献
20.
Bin Wang Fuliang Lyu Shuang Li Jian Li Zhili Yang Li Li Xuefeng Wang Yintao Lu Taotao Yang Jingwu Wu Guozhong Sun Hongxia Ma Xiaoyong Xu 《海洋学报(英文版)》2021,40(3):84-93
High-resolution multichannel seismic data enables the discovery of a previous, undocumented submarine canyon(Huaguang Canyon) in the Qiongdongnan Basin, northwest South China Sea. The Huaguang Canyon with a NW orientation is 140 km in length, and 2.5 km to 5 km in width in its upper reach and 4.6 km to 9.5 km in width in its lower reach. The head of the Huaguang Canyon is close to the Xisha carbonate platform and its tail is adjacent to the central canyon. This buried submarine canyon is formed by gravity flows from the Xisha carbonate platform when the sea level dropped in the early stage of the late Miocene(～10.5 Ma). The internal architecture of the Huaguang Canyon is mainly characterized by high amplitude reflections, indicating that this ancient submarine canyon was filled with coarse-grained sediments. The sediment was principally scourced from the Xisha carbonate platform. In contrast to other buried large-scale submarine canyons(central canyon and Zhongjian Canyon) in the Qiongdongnan Basin, the Huaguang Canyon displays later formation time, smaller width and length, and single sediment supply. The coarse-grained deposits within Huaguang Canyon provide a good environment for reserving oil and gas, and the muddy fillings in Huaguang Canyon have been identified as regional caps. Therefore, Huaguang Canyon is potential area for future hydrocarbon exploration in the northwest South China Sea. Our results may contribute to a better understanding of the evolution of submarine canyons formed in carbonate environment. 相似文献