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1.
利用高分辨率三维地震资料、测井和钻井数据,对东非鲁伍马盆地深水沉积特征进行了系统刻画。根据深水沉积体的地震相特征,识别出峡谷、水道、漫溢沉积、朵体、块体搬运沉积(MTDs)和凝缩段等深水沉积单元,建立了地震识别图版。分析总结了水道和朵体的岩性特征、电性特征和储层物性特征,砂岩具有低伽马(GR)和高电阻(RT)特征,厚层砂岩GR曲线呈“箱型”,有泥岩夹层的砂岩段呈叠加的“钟型”特点;储层压实程度弱,发育原生粒间孔隙,具有中—高孔、中—高渗的特征。结合成藏条件研究,认为由水道和朵体浊积砂岩储层、凝缩段和漫溢沉积泥岩盖层、天然堤和MTDs为侧向遮挡等要素构成的油气储、盖配置关系,是研究区油气成藏的一个关键因素,对深水油气勘探具有一定的指导意义。 相似文献
2.
The mudrock log-derived compaction curve is a significant tool for investigating the primary migration of hydrocarbon, predicting fluid overpressure, estimating formation erosion thicknesses and restoring the buried history and paleo-structure of a basin. However, the presence of kerogen in organic-rich shales can create typically high logging values of the acoustic transit time. Thus, the abnormally high values of the acoustic transit time for organic-rich rocks may not truly reflect the porosity variations of subsurface rocks, leading to great uncertainties in the understanding of the mudstone compaction and a certain amount of error in the abnormal fluid pressure estimation when using the mudrock log-derived compaction curve. Therefore, it is necessary to recalibrate the mudstone compaction curve by eliminating the increment of the acoustic transit time caused by the kerogen content of organic-rich mudstones. Taking the southwest Ordos Basin as an example, this paper presents a new equivalent volume model based on the composition of organic-rich shale in which the kerogen content is also considered. Based on the quantitative relationship between the rock composition and the acoustic transit time, a quantitative formula for calculating the acoustic transit time increment caused by the kerogen is derived. This formula shows that the increment depends not only on the organic content but also on the occurrence state, pore size, pore fluid composition and other factors. X-ray diffraction (XRD) data were used to determine the main mineral composition of the mudstone and to calculate the acoustic transit time of the rock skeleton. Then, the mudstone compaction curve in the Zhenjing area was calibrated by combining the measured porosity and total organic carbon (TOC) of the mudstone based on the correction formula. The compaction characteristics varied significantly between before and after the calibration. The slope of the normal compaction trend (NCT) line decreased by 30–55%, and the acoustic transit time deviation from the NCT in the undercompaction interval decreased significantly. The overpressure at the maximum burial depth estimated by the equivalent depth method is in better agreement with the results obtained by numerical simulation after the calibration, and the porosity determined from the well log after the calibration is also closer to the true measured value. The method proposed in this paper is of great significance for improving the reliability and accuracy of compaction research on organic-rich mudstones, especially for the accurate estimation of abnormal pressure in the source rock layer. Additionally, it can be used as an effective reference for mudstone compaction studies in similar geological settings areas or basins. 相似文献
3.
在详细调研国内外页岩气储层非均质性研究的基础上,以四川盆地下寒武统筇竹寺组为例,通过平面、层内和微观3个方面分析了泥页岩非均质性特征。平面非均质性主要受区域沉积特征和泥页岩有机地球化学特征控制,盆地中西部主要发育泥质砂岩和砂质泥岩,总有机碳含量TOC和有机质成熟度相对较低;东北部泥质灰岩发育,TOC和有机质成熟度较高;南部以碳质泥页岩为主,TOC和有机质成熟度最高(镜质体反射率Ro可达4.0%)。连井剖面和单井泥岩层矿物特征分析表明,层内非均质性较强,主要表现为横向上地层总厚度、泥页岩单层厚度、泥页岩发育层数、夹层特征和顶—底板岩性沿剖面变化快,纵向上矿物成分和岩石脆性度差异明显。微观非均质性主要受孔隙类型和基质微裂缝影响,黏土层间孔隙和有机质孔隙发育,基质微裂缝对沟通孔隙起主要作用。综合分析认为,四川盆地下寒武统筇竹寺组页岩气储层非均质性特征明显,对页岩气井产能和页岩气采收率有重要影响。 相似文献
4.
琼东南盆地新近系莺二段物源体系及其控制下的深水重力流沉积 总被引：1，自引：0，他引：1
近年来在琼东南盆地超深水区莺歌海组发现了多个深水气藏,展现了广阔的勘探前景。但随着油气勘探进一步推进,关于莺二段的储层物性问题日益凸显,严重制约了下一步的勘探进程。本文研究基于前人总结的区域地质资料,结合岩芯、测井和三维地震等资料,建立了莺二段三级层序格架,综合分析了层序格架内物源体系及其控制下的重力流沉积特征。研究表明,重力流沉积体系主要发育在莺二段下、中层序,具有南、北、轴向三大物源体系。不同物源体系控制了重力流储集体的空间展布和沉积特征:(1)南物源控制的海底峡谷充填深海泥岩,而北物源控制的海底峡谷充填的厚层浊积水道砂岩,孔渗物性好,是良好的储集层;(2)轴向物源影响的溢岸漫滩沉积,由于物性条件好,可以作为良好的油气储层;(3)南物源控制海底扇砂岩的厚度薄、粒度细、泥质含量较高,而北物源和轴向物源供应的海底峡谷和海底扇朵体的砂体面积广、厚度大、粒度粗、物性好,是深水区莺二段最重要的优质产气储层。 相似文献
5.
Dongxia Chen Xiongqi Pang Zhenxue Jiang Jianhui Zeng Nansheng Qiu Maowen Li 《Marine and Petroleum Geology》2009
A great difference exists between the hydrocarbon charging characteristics of different Tertiary lacustrine turbidites in the Jiyang Super-depression of the Bohai Bay Basin, east China. Based on wireline log data, core observation and thin-section analyses, this study presents detailed reservoir property data and their controlling effects from several case studies and discusses the geological factors that govern the hydrocarbon accumulation in turbidite reservoirs. The lacustrine fluxoturbidite bodies investigated are typically distributed in an area of 0.5–10 km2, with a thickness of 5–20 m. The sandstones of the Tertiary turbidites in the Jiyang Super-depression have been strongly altered diagenetically by mechanical compaction, cementation and mineral dissolution. The effect of compaction caused the porosity to decrease drastically with the burial depths, especially during the early diagenesis when the porosity was reduced by over 15%. The effect of cementation and mineral dissolution during the late-stage diagenesis is dominated by carbonate cementation in sandstones. High carbonate cement content is usually associated with low porosity and permeability. Carbonate dissolution (secondary porosity zone) and primary calcite dissolution is believed to be related to thermal maturation of organic matter and clay mineral reactions in the surrounding shales and mudstone. Two stages of carbonate cementation were identified: the precipitation from pore-water during sedimentation and secondary precipitation in sandstones from the organic acid-dissolved carbonate minerals from source rocks. Petrophysical properties have controlled hydrocarbon accumulation in turbidite sandstones: high porosity and permeability sandstones have high oil saturation and are excellent producing reservoirs. It is also noticed that interstitial matter content affects the oil-bearing property to some degree. There are three essential elements for high oil-bearing turbidite reservoirs: excellent pore types, low carbonate cement (<5%) and good petrophysical properties with average porosity >15% and average permeability >10 mD. 相似文献
6.
Delta-front sand bodies with large remaining hydrocarbon reserves are widespread in the Upper Cretaceous Yaojia Formation in the Longxi area of the Western Slope, Songliao Basin, China. High-resolution sequence stratigraphy and sedimentology are performed based on core observations, well logs, and seismic profile interpretations. An evaluation of the reservoir quality of the Yaojia Formation is critical for further petroleum exploration and development. The Yaojia Formation is interpreted as a third-order sequence, comprising a transgressive systems tract (TST) and a regressive systems tract (RST), which spans 4.5 Myr during the Late Cretaceous. Within this third-order sequence, nine fourth-order sequences (FS9–FS1) are recognized. The average duration of a fourth-order sequence is approximately 0.5 Myr. The TST (FS9–FS5) mostly comprises subaqueous distributary channel fills, mouth bars, and distal bars, which pass upward into shallow-lake facies of the TST top (FS5). The RST (FS4–FS1) mainly contains subaqueous distributary-channel and interdistributary-bay deposits. Based on thin-sections, X-ray diffraction (XRD), scanning electron microscope (SEM) and high-pressure mercury-intrusion (HPMI) analyses, a petrographic study is conducted to explore the impact of the sedimentary cyclicity and facies changes on reservoir quality. The Yaojia sandstones are mainly composed of lithic arkoses and feldspathic litharenites. The sandstone cements mostly include calcite, illite, chlorite, and secondary quartz, occurring as grain coating or filling pores. The Yaojia sandstones have average core plug porosity of 18.55% and permeability of 100.77 × 10−3 μm2, which results from abundant intergranular pores and dissolved pores with good connectivity. Due to the relatively coarser sediments and abundant dissolved pores in the feldspars, the FS4–FS1 sandstones have better reservoir quality than the FS9–FS5 sandstones, developing relatively higher porosity and permeability, especially the FS1 and FS2 sandstones. The source–reservoir–cap-rock assemblages were formed with the adjoining semi-deep lake mudstones that were developed in the Nenjiang and Qingshankou Formations. This study reveals the deposition and distribution of the delta-front sand bodies of the Yaojia Formation within a sequence stratigraphic framework as well as the factors controlling the Yaojia sandstones reservoir quality. The research is of great significance for the further exploration of the Yaojia Formation in the Longxi area, as well as in other similar lacustrine contexts. 相似文献
7.
The hydrate-bearing sediments above the bottom simulating reflector (BSR) are associated with low attenuation or high quality factor (Q), whereas underlying gas-bearing sediments exhibit high attenuation. Hence, estimation of Q can be important for qualifying whether a BSR is related to gas hydrates and free-gas. This property is also useful for identifying gas hydrates where detection of BSR is dubious. Here, we calculate the interval Q for three submarine sedimentary layers bounded by seafloor, BSR, one reflector above and another reflector below the BSR at three locations with moderate, strong and no BSR along a seismic line in the Makran accretionary prism, Arabian Sea for studying attenuation (Q−1) characteristics of sediments. Interval Q for hydrate-bearing sediments (layer B) above the BSR are estimated as 191 ± 11, 223 ± 12, and 117 ± 5, whereas interval Q for the underlying gas-bearing sediments (layer C) are calculated as 112 ± 7, 107 ± 8 and 124 ± 11 at moderate, strong and no BSR locations, respectively. The large variation in Q is observed at strong BSR. Thus Q can be used for ascertaining whether the observed BSR is due to gas hydrates, and for identifying gas hydrates at places where detection of BSR is rather doubtful. Interval Q of 98 ± 4, 108 ± 5, and 102 ± 5, respectively, at moderate, strong and no BSR locations for the layer immediately beneath the seafloor (layer A) show almost uniform attenuation. 相似文献
8.
Deep marine tight sandstone oil reservoirs are the subject of considerable research around the world. This type of reservoir is difficult to develop due to its low porosity, low permeability, strong heterogeneity and anisotropy. A marine tight sandstone oil reservoir is present in the Silurian strata in the northern Tazhong area of the Tarim Basin, NW China, at a depth of more than 5000 m. The porosity is between 6% and 8%, and the gas permeability is between 0.1 and 1 × 10−3 μm2. The features of this type of reservoir include the poor effects of conventional fracturing modifications and horizontal wells, which can lead to stable and low levels of production after staged fracturing. Here, we conduct a comprehensive evaluation of the mechanical properties of the rock and the in situ stress of the target tight sandstones by using numerous mechanical and acoustic property tests, conducing crustal stress analysis and using data from thin section observations. The dispersion correction technique is used to transform velocity at the experimental high frequency (1 MHz) to velocity at the logging frequency (20 kHz). The logging interpretation models of the transverse wave offset time, mechanical parameters and in situ stress are calculated, and each model represents a high precision prediction. Simulating the in situ stress field of the Silurian strata using a three-dimensional finite element method demonstrates that the average error between the simulation result and the measured value is less than 6%. The planar distribution of each principal stress is mainly controlled by the burial depth and fault distribution. By conducting in situ stress orientation analysis for the target layer via the analysis of paleomagnetism, borehole enlargement, fast shear wave orientation and stress field simulation, we show that the direction of the maximum horizontal stress is N45E. In this paper, a typical and successful comprehensive evaluation of the stress field of the deep tight sandstone oil reservoir is provided. 相似文献
9.
Shuo Chen Renhai Pu Huiqiong Li Hongjun Qu Tianyu Ji Siyu Su Yunwen Guan Hui Zhang 《海洋学报(英文版)》2022,41(9):86-106
The Dongfang1-1 gas field (DF1-1) in the Yinggehai Basin is currently the largest offshore self-developed gas field in China and is rich in oil and gas resources. The second member of the Pliocene Yinggehai Formation (YGHF) is the main gas-producing formation and is composed of various sedimentary types; however, a clear understanding of the sedimentary types and development patterns is lacking. Here, typical lithofacies, logging facies and seismic facies types and characteristics of the YGHF are identified based on high-precision 3D seismic data combined with drilling, logging, analysis and testing data. Based on 3D seismic interpretation and attribute analysis, the origin of high-amplitude reflections is clarified, and the main types and evolution characteristics of sedimentary facies are identified. Taking gas formation upper II (IIU) as an example, the plane distribution of the delta front and bottom current channel is determined; finally, a comprehensive sedimentary model of the YGHF second member is established. This second member is a shallowly buried “bright spot” gas reservoir with weak compaction. The velocity of sandstone is slightly lower than that of mudstone, and the reflection has medium amplitude when there is no gas. The velocity of sandstone decreases considerably after gas accumulation, resulting in an increase in the wave impedance difference and high-amplitude (bright spot) reflection between sandstone and mudstone; the range of high amplitudes is consistent with that of gas-bearing traps. The distribution of gas reservoirs is obviously controlled by dome-shaped diapir structural traps, and diapir faults are channels through which natural gas from underlying Miocene source rocks can enter traps. The study area is a delta front deposit developed on a shallow sea shelf. The lithologies of the reservoir are mainly composed of very fine sand and coarse silt, and a variety of sedimentary structural types reflect a shallow sea delta environment; upward thickening funnel type, strong toothed bell type and toothed funnel type logging facies are developed. In total, 4 stages of delta front sand bodies (corresponding to progradational reflection seismic facies) derived from the Red River and Blue River in Vietnam have developed in the second member of the YGHF; these sand bodies are dated to 1.5 Ma and correspond to four gas formations. During sedimentation, many bottom current channels (corresponding to channel fill seismic facies) formed, which interacted with the superposed progradational reflections. When the provenance supply was strong in the northwest, the area was dominated by a large set of delta front deposits. In the period of relative sea level rise, surface bottom currents parallel to the coastline were dominant, and undercutting erosion was obvious, forming multistage superimposed erosion troughs. Three large bottom current channels that developed in the late sedimentary period of gas formation IIU are the most typical. 相似文献
10.
白云深水区多口油气钻探揭示砂质储层含气和含水都有可能表现为Ⅲ类或Ⅳ类的AVO及亮点异常，单纯依靠亮点+Ⅲ类AVO异常进行烃类气体预测具有多解性，是钻前储层的流体预测面临的新挑战和难点。本文利用珠江口盆地白云深水区测井数据，根据储层特征与含气性差异性优选了多口测井数据齐全井，利用测井数据对不同井位储层段的AVO特征进行分析。通过Aki-Richards公式计算了不同井的截距和梯度属性，建立了白云深水区P和G属性图版。对比分析发现不同含气储层，随着岩性、含气性差异及其岩性组合不同，呈现不同AVO异常特征，岩心分析表明该异常不仅与储层含气性有关，也与盖层岩性密切相关，尤其是当盖层或者储层含有灰岩时，对AVO异常影响较大。利用M矿区目标储层的叠前反演弹性参数，再结合本文建立的P和G属性图版和流体识别因子方法，对目标储层含气性进行了预测，发现了该储层在横向上含气性不同，钻探结果证实预测结果有效与可靠，表明该AVO模板具有较好的实用性。 相似文献
11.
由于存在部分泥岩井眼垮塌，东海春晓气田测井曲线砂泥岩阻抗部分叠置。针对这一现象，采用未垮塌段泥岩伽马与密度拟合关系校正垮塌段泥岩密度，声波时差经本区伽德那公式拟合后求取。通过泥岩垮塌测井数据校正前后对比、直方交会、岩石物理、正演及反演效果分析，认为校正后的测井数据比较真实地反映垮塌段扩径泥岩地层特征，储层与围岩波阻抗差异明显，为储层反演、砂体空间展布分析提供了有力依据。 相似文献
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13.
Reservoir pressures within the Bullwinkle minibasin (Green Canyon 65, Gulf of Mexico continental slope) increase at a hydrostatic gradient whereas pressures predicted from porosity within mudstones bounding these reservoirs increase at a lithostatic gradient: they are equal at a depth 1/3 of the way down from the crest of the structure. Two- and three-dimensional steady-state flow models demonstrate that bowl-shaped structures will have lower pressures than equivalent two-dimensional structures and that if a low permeability salt layer underlies the basin, the pressure is reduced. We conclude that at Bullwinkle, pressure is reduced due to an underlying salt body and the bowl-shape of the basin. A geometric approach to predict sandstone pressure is to assume that the reservoir pressure equals the area-weighted average of the mudstone pressure. When the mudstone pressure gradient is constant, as at Bullwinkle, the reservoir pressure equals the mudstone pressure at the average depth (centroid) of the reservoir. 相似文献
14.
Lacustrine deep-water turbidite plays are a novel area for exploration in the Huimin Depression, Bohai Bay Basin. Turbidites in the Shang 847 block, a typical turbidite play in the Huimin Depression, provide an opportunity to study the factors controlling the reservoir properties and hydrocarbon accumulation in lacustrine turbidite sandstones. The reservoir quality of turbidite sandstones (very fine-grained, moderately to well sorted, mainly lithic arkose) in this study area are mainly controlled by the distribution patterns of carbonate cements and pseudomatrix. Significant inverse relationships exist between the volume of carbonate cement and both porosity and permeability of the turbidite sandstones. Carbonate cement is located preferentially near the margins of the sandstone bodies. Sandstones with distance from the sandstone–mudstone contact surface less than 0.7 m or with thickness less than 1.2 m are commonly tightly cemented (carbonate cement >15%) with low porosity and permeability (lower than 10% and 0.1 mD, respectively). The source of carbonate cement was most likely external, probably derived from the surrounding mudstone. Most pore-filling carbonate cements occurred during late diagenesis at burial depths greater than 2200 m. The petrophysical properties of turbidites have a positive relationship with the content of kaolinite and chlorite, but have a negative relationship with the content of illite. 2-D and 3-D reconstructions of non-oil bearing and oil-bearing layers indicate that dissolution of carbonate cement, feldspars and unstable rock fragments was more developed in oil-bearing layers than in non-oil bearing layers and hance oil-bearing layers have higher porosity and larger pore sizes. Petrophysical property appears to have a significant effect on the hydrocarbon accumulation in the turbidite sandstones. Sandstones with porosities lower than 9% and/or permeabilities lower than 0.78 mD are not prone to contain oil. 相似文献
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16.
Only a limited number of comparative studies have explored the diagenetic differences of reservoirs caused by the charging of natural gases with different compositions during the migration and accumulation of oil and gas. In this study, we quantitatively assessed the diagenetic variations of the lower Zhuhai Formation reservoirs in the WC-A sag, the Pearl River Mouth Basin, as a result of natural gas charging with different compositions. The employed methods included electron microscopy, scanning electron microscopy, cathode luminescence, X-ray diffraction, chemical composition analysis of formation water, stable isotope analysis, and fluid inclusion determination. The results indicated that: (1) in the lower Zhuhai Formation reservoir that are near the large fractures, the late-charging of CO2-rich thermal fluid promoted the dissolution of minerals, and changed the porosity, permeability, pH value of fluid, and the contents of ions such as K+, Na+, Mg2+ of the reservoirs. These changes, in turn, indirectly affected the content, form, and distribution of clay minerals in the reservoirs. In addition, the secondary enlargement of quartz was enhanced. (2) The charging of CO2-rich thermal fluid caused strong dissolution and produced high contents of cements. The dissolution mainly occurred in a half open system with strong fluid activity. Consequently, the significantly decreasing of permeability was hindered and middle porosity–middle permeability reservoirs were generated. The reservoirs that are far from the large fractures, however, were mainly early charged by the hydrocarbon-rich fluid. The dissolution was weak and the generated cements were limited. In addition, the dissolution products could not be discharged in such closed diagenetic systems. As a result, the permeability of the reservoir was declined sharply and resulted in low porosity–low permeability reservoirs. 相似文献
17.
Thin-bedded beach-bar sandstone reservoirs are common in the Eocene Shahejie Formation (Es4s) of Niuzhuang Sag, along the southern gentle slope of the Dongying Depression. Here we report on the link between sequence stratigraphy, sedimentary facies and diagenetic effects on reservoir quality. Seismic data, wireline logs, core observations and analyses are used to interpret depositional settings and sequence stratigraphic framework. Petrographic study based on microscopic observation of optical, cathodoluminescence (CL), confocal laser scanning (LSCM) and scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses were used to describe the fabric, texture, allogenic and authigenic mineralogy of these highly heterogeneous sandstone reservoirs. The Es4s interval is interpreted as third-order sequence, composed of a lowstand systems tract (LST), a transgressive systems tract (TST) and a highstand systems tract (HST). On the fourth order, twenty-nine parasequences and seven parasequence sets have been identified. Sand bodies were deposited mainly in the shoreface shallow lake beach-bar (clastic beach-bar), semi-deep lake (carbonate beach-bar) and the fluvial channels. The depositional and diagenetic heterogeneities were mainly due to the following factors: (1) fine grain size, poor sorting, and continuous thin inter-bedded mud layers with siltstone/fine-sandstone having argillaceous layers in regular intervals, (2) immature sediment composition, and (3) even with the dissolution of grains and several fractures, destruction of porosity by cementation and compaction. Secondary pores from feldspar dissolution are better developed in sandstones with increased cementation. Grain coating smectite clays preserved the primary porosity at places while dominating pore filling authigenic illite and illite/smectite clays reduced permeability with little impact on porosity. Due to the high degree of heterogeneity in the Es4s beach-bar interval, it is recognized as middle to low permeable reservoir. The aforementioned study reflects significant insight into the understanding of the properties of the beach-bar sands and valuable for the comprehensive reservoir characterization and overall reservoir bed quality. 相似文献
18.
A seismic refraction study on old (110 Myr) lithosphere in the northwest Pacific Basin has placed constraints on crustal and uppermantle seismic structure of old oceanic lithosphere, and lithospheric aging processes. No significant lateral variation in structure other than azimuthally anisotropic mantle velocities was found, allowing the application of powerful amplitude modeling techniques. The anisotropy observed is in an opposite sense to that expected, suggesting the tectonic setting of the area may be more complex than originally thought. Upper crustal velocities are generally larger than for younger crust, supporting current theories of decreased porosity with crustal aging. However, there is no evidence for significant thickening of the oceanic crust with age, nor is there any evidence of a lower crustal layer of high or low velocity relative to the velocity of the rest of Layer 3. The compressional and shear wave velocities rule out a large component of serpentinization of mantle materials. The only evidence for a basal crustal layer of olivine gabbro cumulates is a 1.5 km thick Moho transition zone. In the slow direction of anisotropy, upper mantle velocities increase from 8.0 km s-1 to 8.35 km s-1 in the upper 15 km below the Moho. This increase is inconsistent with an homogeneous upper mantle and suggests that compositinal or phase changes occur near the Moho. 相似文献
19.
S. A. Mosharov 《Oceanology》2010,50(6):884-892
The studies were performed from September 10 to 29 of 2007 in the Kara Sea in transects westward of the Yamal Peninsula, near
the St. Anna Trough, in the Ob River’s estuary, and on the adjacent shelf. The concentration of chlorophyll a in the euphotic layer changed from 0.02 to 4.37 mg/m3, amounting on the average to 0.76 mg/m3. The primary production in the water column varied from 10.9 to 148.0 mg C/m2 per day (the mean was 56.9 mg C/m2 per day). It was shown that frontal zones divided the Kara Sea into distinct areas with different productivities. The maximum
levels of the primary production were measured in the deep part of the Yamal transect (132.4 mg C/m2 per day) and the shallow Kara Sea shelf near the Ob River’s estuary (74.9 mg C/m2 per day). The characteristics of these regions were the low salinity of the surface water layer (19–25 psu) and the elevated
silicon content (12.8–28.1 μg-atom Si/l), which is explainable by the river water inflow. The frontal zones of the Yamal Current
in the Yamal and Ob transects displayed high values of the assimilation numbers, amounting to 2.32 and 1.49 mg C/mg of chlorophyll
per h, respectively (the maximal for the studied regions). 相似文献
20.
Gwang-Soo Lee Gwang-Hoon Lee Soo-Choul Park Gil-Young Kim Dong-Geun Yoo 《Marine Georesources & Geotechnology》2013,31(2):96-114
High-resolution seismic survey and sediment core sampling were conducted to investigate acoustic characteristics of gas-bearing sediments in Jinhae Bay, the southeast of Korea. The sediment in Jinhae Bay is mostly homogenous mud deposited after the Holocene transgression. Along with the 410 km of chirp seismic profiling, five piston core samples were collected on the track lines. Gassy sediments are common and occur widely in the bay. Core samples were analyzed for sediment texture, physical properties (porosity, water content, bulk density, and grain density), acoustic properties (compressional wave velocity and attenuation), and electrical resistivity. X-radiograph image analysis was also performed to observe the shape of degassing cracks. There is no significant downcore variation on physical and sediment textures regardless of existence of gas bubbles. However, compressional wave velocity dramatically decreases from average 1480 to 1380～739 m/s for the cores that penetrate the gas-bearing zones. This is probably due to degassying cracks that developed by escaping gases and free gas bubbles that are still trapped in the cores. Electrical resistivity is the only geotechnical property that increases in the gas-bearing zone where compressional wave velocity abruptly decreases. This indicates the possibility of using both electrical resistivity as an index variable as well as to compressional wave velocity to identify gassy sediment microstructure because there are little changes in texture and composition of sediment. 相似文献