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1.
浅层气逸出到海水中的气泡声学探测方法 总被引：4，自引：0，他引：4
针对南黄海西部等地区在海洋调查仪器上发现的海水中浅层气逸出气泡产生的声学羽流等气泡记录,首先根据水体中气泡共振发生非线性振动形成的强烈散射现象,计算了我国浅层气分布海区的常见浅层气逸出气泡共振频率范围、不同调查仪器在水深变化时的探测气泡大小,据此分析了不同调查仪器探测浅层气逸出气泡的范围。其次,根据气泡在水中的变化、运动规律,提出了浅层气逸出气泡应当具备的声学特点,排除了南黄海西部地区形成水体中特征反射的其他可能因素,并探讨了云状扰动的可能形成原因。 相似文献
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海底浅层圈闭与浅层气地震反射特征对比 总被引：1，自引：0，他引：1
海底浅层圈闭条件是决定浅层气反射特征的重要因素,根据海底浅层圈闭条件的分析、国内外浅层气分布区反射特征与底质类型对比分析和南黄海西部地区浅部断层分析,得出结论:(1)浅层气的圈闭条件主要受海底底质类型与浅部断层控制,常见圈闭类型为岩性圈闭和断层圈闭;(2)底质类型是决定浅层气反射特征的重要因素。分析认为海底表层沉积物的泥砂含量决定了圈闭中盖层封闭能力,进而决定了浅层气聚集能力和储集量,形成不同浅层气地震反射特征;(3)某些现代三角洲地区,受潮流或河流与海洋共同作用影响,表层底质经常与整个浅层的物质组成差别较大。由于其内部一般含有较厚的细颗粒黏土质粉砂和粉砂质黏土,封闭能力较强,可封闭较多浅层气,能形成大规模的声学空白反射,但常观察到浅层气反射顶界面局部突起呈旗舰状;(4)浅部断层既可形成断层圈闭,也可充当浅层气的运移通道。断层圈闭通常较少见且难以识别,浅部断层在第四纪松散地层中更多地充当了浅层气运移的通道;(5)浅部地层存在多套含泥较多的地层且形成圈闭时,浅层气被多次圈闭,会在不同深度形成"楼层式"的多个强反射界面、声学扰动。 相似文献
3.
《海洋地质与第四纪地质》2016,(1)
通过对长江口外海域浅层气地震反射特征的研究,发现该地区浅层气地震反射形态特征丰富,按不同形态特征分类如下:(1)按整体形态特征分为:幕状反射、柱状反射、气烟囱状反射;(2)按顶界面形态特征分为:不规则顶界面、较规则顶界面;(3)按侧面形态特征分为:侧面竖直、侧向突出;(4)按组合形态特征分为:垂向多层强反射、横向间断的浅层气反射、竖向变化的浅层气反射。总结了调查区内浅层气反射形态特征的分布规律,编制了长江口外海域浅层气分布图。讨论了浅层气反射区内部的强反射分布形态与浅层气空间运移路径的对应关系。 相似文献
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《中国海洋大学学报(自然科学版)》2017,(11)
海底浅层气严重影响海底地层的结构稳定性,因此成为近海海洋工程的重要安全因素。近年来,通过地震手段在渤海海域发现了多处疑似浅层气区域。该区域中的浅层气蕴藏在海底以下地层或通过断层从地层溢出到海水中。本文在渤海海域高分辨率地震勘探等物探调查资料基础上,分析了渤海海域浅层气地震反射特征。通过查阅相关资料,总结渤海海域浅层气的一般成因。在将已发现的渤海海域浅层气分布区域进行总结并绘制分布图的同时,结合了渤海地质演化以及沉积历史,推测了渤海浅层气集中分布区域的成因。最后讨论了浅层气对近海海洋工程的严重危害。本文所研究的渤海海域海底浅层气分布情况可以为渤海海域海洋工程建设提供重要参考。 相似文献
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海底麻坑是由地层中流体向海底快速喷发或缓慢渗漏所形成的一种凹陷地貌,对其形态及成因机理进行深入研究具有重要意义。本研究基于高分辨率多波束地形、侧扫声纳、浅地层剖面及多道地震探测数据,对舟山群岛东部青浜岛海域发育的麻坑及其微地貌进行研究,分析表明:研究区发育有3个大型麻坑,并受到NE—SW向底流的改造而出现不同程度沿此方向的拉长,呈新月形或拉长形。麻坑侧壁呈现西陡东缓、西高东低的特征。3个大型麻坑内部发育有小的次级单元麻坑,或形成复合麻坑和链状麻坑等。麻坑之下地层出现声学浑浊等浅层气特征反射。在麻坑内外分别钻孔取样进行烃类气体的同位素分析,结果表明形成麻坑的流体为生物成因的甲烷气。研究区3个大型麻坑是在台风活动诱发下,由第四系地层中的甲烷气猛烈喷溢形成,而麻坑微地貌则是在随后发生的海底浅层气小规模缓慢逃逸形成的。 相似文献
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南海北部白云凹陷-东沙岛西南海区的浅地层探测与深水沉积特点 总被引：1，自引：0，他引：1
采用新引进的海洋深水浅层剖面仪,从珠江口外陆架进入白云凹陷-东沙岛西南海区中陆坡区,进行了浅地层探测,获得了高分辨率反射记录.分析发现,白云凹陷上陆坡段沉积连续性较好,海底反射强度侧向变化平缓,显示了比较均一的沉积底质和微弱的海底水动力条件;在白云凹陷-东沙岛西南海区中陆坡区,海底滑坡严重,局部存在强烈的、平行陆坡的海底洋流冲蚀,海底地形崎岖不平,反射强度侧向变化大,表明海底底质不均匀,海底水动力强.浅地层记录还显示中陆坡海底山丘有海底气体泄露现象,结合常规反射地震识别的海底泥底辟特征,确定海底山丘为泥火山.气体泄露和海底反射振幅的变化代表了海底浅层聚有丰富的气体以及嗜甲烷生物链活动的钙化,因而推断该区不仅是油气的聚集区,也是水合物的聚集带. 相似文献
9.
黄东海灾害地质类型及声学反射特征 总被引：2，自引：0，他引：2
高分辨率声学剖面资料是识别海洋灾害地质现象的有效手段。该文利用国家“12 6”专项调查在黄东海海域获得的各种声学剖面及历史资料 ,在黄东海海底及浅层识别出多种灾害地质类型 ,如潮成沙脊、沙波、古河道、断层、浅层气等。根据对它们的声学特征及成因机制的分析 ,作者认为 :潮流是黄东海海底表层灾害地质形成的主要动力因素 ;而浅层灾害地质因素以古河道、断层、浅层气等为主。 相似文献
10.
南黄海西部浅部地层地震层序及其沉积特征 总被引：2，自引：0，他引：2
南黄海陆架在第四纪具有海侵—海退交替发生、海陆相地层交互沉积的特点,沉积相及其分布主要受海平面变化与古河流及其三角洲的控制。对南黄海西部地区采集的5600km浅层地震剖面进行了层序划分与解释,得到以下认识:(1)早更新世晚期以来的南黄海地层可分为U1—U14共14个地震地层单元,组成6个地震层序,代表了6次大规模海侵-海退过程,其中氧同位素5期海相地层在该地区最发育;(2)根据全新世地层厚度变化,将该区分为6个沉积区:东部弱沉积区、中北部沉积发育区、海州湾外侵蚀区、废黄河口沉积区、射阳河口岸外侵蚀区和苏北浅滩沉积区;(3)氧同位素6期至2期,南黄海西部陆相层内发育了3期埋藏古河道:上层古河道发育于氧同位素2期,古长江水系、古黄河水系分别自南黄海南部、北部流入古黄海;中层古河道发育于氧同位素4期,仅分布于近岸地区;下层古河道发育于氧同位素6期,分布于123°E以西地区,其南部古河道应为古长江水系,规模较大,其北部古河道规模较小,分布范围有限;(4)古长江第四纪早期在古黄海入海,古黄河在氧同位素5期中后期也开始自古黄海入海,其古河道发育具有一定继承性,后期发育规模逐渐增大;(5)气候温暖的高海面时期发育于构造沉降... 相似文献
11.
南黄海西部海域高分辨率声学地层及其沉积环境 总被引：4，自引：0，他引：4
通过对高分辨率浅地层剖面的分析解译,对南黄海西部陆架区进行了声学地层划分。南黄海西部海域声学地层剖面可划分为5套地层Ⅰ、Ⅱ1、Ⅱ2、Ⅲ1、Ⅲ2,每套地层代表一次全球性(或区域性)海平面变化周期内的海进一海退这样一个完整的旋回变化过程所形成的海侵或海退沉积层序。将典型声学地层剖面与区内钻孔岩心的沉积地层岩性单元对比研究,得到各声学反射层的时代、岩性及沉积环境。并发现依据浅地层进行的声学地层划分与钻孔岩心的地质地层划分有较好的对应关系。结合区内钻孔岩心的分析结果,对晚更新世以来南黄海陆架区的沉积环境及沉积过程进行了探讨。 相似文献
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San Simón Bay in the innermost part of the Ría de Vigo is characterized by an abundance of very shallow gas accumulations
and methane seeps. During the expeditions of April–June–September 2004 within the Spanish-funded Gs2G project, detailed very
high-resolution seismic and field investigations were carried out to study the shallow gas and the seeps. Direct gas fluxes
also were measured from bubble streams. For the first time, the surface area and gas front depth of a shallow gas field has
been mapped and quantified in the inner bay of Ría de Vigo. This field overlaps spatially with the distribution of Holocene
mud within the bay. Seismic data show 3.6 km2 affected by acoustic turbidity but this surface can be extended up to 9.5 km2 of San Simón’s muddy subtidal area. Mounded turbidity superimposed on the main gas field has been mapped and characterized
as anthropogenically (mussel rafts) mediated gas accumulations. Different acoustic anomalies have been identified and interpreted
as being due to gas escapes from the present seabed sediment. The very high resolution of the seismic data makes it possible
to identify a new type of seep, here named ‘acoustic smoke.’ A direct relationship can be observed between the gas front of
accumulations and escape features, both acoustic seeps and pockmarks. The methane flux has been estimated from the subtidal
environment in San Simón based on detected acoustic targets and direct measurements of current bubble flow. The total estimated
methane flux from the seabed into the water column ranges from 10.1 to 48.8 t/year, and into the atmosphere from 7.0 to 34.2 t/year.
The intertidal San Simón environment is also actively venting methane, as indicated by the presence of bubbling during high
tide and white patches of Beggiatoa sp. 相似文献
14.
海底天然气渗漏是海洋环境中广泛分布的自然现象,在世界各大洋中都有发现。海底渗漏的气体赋存于浅部地层,可以改变近表层沉积物的物理性质,使其在声学剖面上得以反映。通过对南海北部陆坡某海域研究区浅地层剖面和地震数据分析,在浅地层剖面上发现了声空白、声混浊、增强反射层、速度下拉等特征,在地震剖面上则识别出气烟囱或泥底辟、亮点、速度下拉、增强反射层等特征。以似海底反射层（BSR）作为地震剖面上明显的含气层标志,划分了2套含气系统。通过浅地层剖面与地震剖面联合解释认为,BSR之下气烟囱／泥底辟的发育导致了亮点、速度下拉、增强反射层等声学特征的发生,BSR之上水合物层的存在则可能起到封堵天然气而使其发生侧向运移的作用,在气体封堵相对薄弱的位置,天然气向上运移形成声空白、声混浊、增强反射层、速度下拉等特征。以声空白代表的天然气聚集带可能成为块状水合物的发育场所,可能成为较有潜力的勘探目标。 相似文献
15.
南海东北部陆坡天然气水合物区的滑塌和泥火山活动 总被引：2，自引：1，他引：1
本文研究了南海东北部陆坡天然气水合物区滑塌和泥火山活动的特征及表现形式,探讨了滑塌和泥火山活动对天然气水合物成藏的影响,提出了滑塌主导和滑塌、泥火山共同作用两种控制模式。根据地震数据、浅层剖面和海底地形数据解释,将研究区划分为规则滑塌区和泥火山活动影响区,并识别出泥火山、泥火山脊、凹槽、凹坑等特征地形。滑塌和泥火山活动是陆坡天然气水合物发育区重要的地形控制因素,两种活动共同作用产生复杂的地形特征。综合多条地震测线中似海底反射层(BSR)形态、连续性和滑塌、泥火山活动的关系,认为滑塌控制的区域,BSR连续,天然气水合物储藏较完整,泥火山活动区天然气水合物储藏也仅受到局部破坏。同时指出滑塌和泥火山活动对研究区长期天然气渗漏活动具有重要作用。 相似文献
16.
Henrique Duarte Luis Menezes Pinheiro Francisco Curado Teixeira José Hipólito Monteiro 《Geo-Marine Letters》2007,27(2-4):115-126
Methane is a powerful greenhouse gas and an important energy source. The global significance and impact in coastal zones of
methane gas accumulation and seepage in sediments from coastal lagoon environments are still largely unknown. This paper presents
results from four high-resolution seismic surveys carried out in the Ria de Aveiro barrier lagoon (Portugal) in 1999, 2002
and 2003. These comprise three chirp surveys (RIAV99, RIAV02, RIAV02A) and one boomer survey (RIAV03). Evidence of extensive
gas accumulation and seepage in tidal channel sediments from the Ria de Aveiro barrier lagoon is presented here for the first
time. This evidence includes: acoustic turbidity, enhanced reflections, acoustic blanking, domes, and acoustic plumes in the
water column (flares). The stratigraphy and structural framework control the distribution and extent of gas accumulations
and seepage in the study area. In these shallow systems, however, tidal altitude variations have a significant impact on gas
detection using acoustic methods, by changing the raw amplitude of the enhanced seismic reflections, acoustic turbidity, and
acoustic blanking in gas-prone areas. Direct evidence of gas escape from drill holes in the surrounding area has shown that
the gas present in the Ria de Aveiro consists of biogenic methane. Most of the gas in the study area was probably generated
mainly in Holocene lagoon sediments. Evidence of faults affecting the Mesozoic limestones and clays underlying some of the
shallow gas occurrences, and the presence of high-amplitude reflections in these deeper units raise the possibility that some
of this gas could have been generated in deeper sedimentary layers, and then migrated upward through the fractured Mesozoic
strata. 相似文献
17.
Very high resolution seismic profiles, ground-truthed by vibrocores, have revealed the occurrence of kilometre-scale acoustic
turbidity in the Marennes-Oléron Bay, France. Such acoustic turbidity is commonly interpreted as gas-charged sediments. Comparison
between accurate historical bathymetric data and the present day bathymetry has shown high sediment accretion zones in the
study area (locally up to 8 m since 1824). The superimposition of seismic and bathymetric datasets displays a striking correlation
between the high sedimentation rate area and the boundaries of the acoustic turbidity, i.e. gas-charged sediments. The key
role of sedimentation rates in shallow gas generation in the study area is pointed out. It is also concluded that shallow
gas is probably generated at short (decadal to secular) time scales. 相似文献
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Dae Choul Kim Gwang Hoon Lee Young Kyo Seo Gil Young Kim Seok Yun Kim Jeong Chang Kim Soo Chul Park Roy Wilkens 《Marine Georesources & Geotechnology》2004,22(1):21-31
Shallow gas in the Korea Strait shelf mud (KSSM) off SE Korea, revealed by high-resolution subbottom profiles, is associated with acoustic blanking, acoustic turbidity, seepages with plumes in the water column, and seafloor depressions. The acoustic blanking, characterized by strong, consistent top reflection and wipeout below, is most dominant. The seaward edge of the acoustic blanking zone generally coincides with the 100-m water-depth contour, suggesting that the water depth (the pressure) may control the distribution of shallow gas. The acoustic turbidity, characterized by diffuse top reflection, is a dark smear, partially blanking the data below. The seepages with plumes, characterized by vertical smearing and disturbed seafloor, are seen only along the shallowest, landward edge of the acoustic blanking zone. This may suggest that the decreased gas solubility at shallow water depths, caused by the lowered pressure, increases the volume of free gas in the sediments, facilitating the gas escape. The seafloor depressions, interpreted as pockmarks, are accompanied by cone-shaped acoustic masking, which is probably the reflection from a narrow vent of gas. The gas-related acoustic anomalies appear to occur mostly in the upper, recent mud of the KSSM. Neither permeable beds nor faults, which can act as vertical migration pathways for deep thermogenic gas, are evident in the recent mud. We interpret that the bacterial degradation of organic matter in situ is the main source for the gas in the KSSM. The upwelling off SE Korea may be an important source for the increased organic matter in the area. 相似文献