Occurrence and exploration of gas hydrate in the marginal seas and continental margin of the Asia and Oceania region   总被引：5，自引：0，他引：5  

Ryo Matsumoto  Byong-Jae Ryu  Sung-Rock Lee  Saulwood Lin  Shiguo Wu  Kalachand Sain  Ingo Pecher  Michael Riedel 《Marine and Petroleum Geology》2011,28(10):1751-1767

Supplies of conventional natural gas and oil are declining fast worldwide, and therefore new, unconventional forms of energy resources are needed to meet the ever-increasing demand. Amongst the many different unconventional natural resources are gas hydrates, a solid, ice-like crystalline compound of methane and water formed under specific low temperature and high pressure conditions. Gas hydrates are believed to exist in large quantities worldwide in oceanic regions of continental margins, as well as associated with permafrost regions in the Arctic. Some studies to estimate the global abundance of gas hydrate suggest that the total volume of natural gas locked up in form of gas hydrates may exceed all known conventional natural gas reserves, although large uncertainties exist in these assessments. Gas hydrates have been intensively studied in the last two decades also due to connections between climate forcing (natural and/or anthropogenic) and the potential large volumes of methane trapped in gas hydrate accumulations. The presence of gas hydrate within unconsolidated sediments of the upper few hundred meters below seafloor may also pose a geo-hazard to conventional oil and gas production. Additionally, climate variability and associated changes in pressure-temperature regimes and thus shifts in the gas hydrate stability zone may cause the occurrence of submarine slope failures.Several large-scale national gas hydrate programs exist especially in countries such as Japan, Korea, Taiwan, China, India, and New Zealand, where large demands of energy cannot be met by domestic supplies from natural resources. The past five years have seen several dedicated deep drilling expeditions and other scientific studies conducted throughout Asia and Oceania to understand gas hydrates off India, China, and Korea. This thematic set of publications is dedicated to summarize the most recent findings and results of geo-scientific studies of gas hydrates in the marginal seas and continental margin of the Asia, and Oceania region.  相似文献   

Structural-stratigraphic control on the Umitaka Spur gas hydrates of Joetsu Basin in the eastern margin of Japan Sea   总被引：1，自引：0，他引：1  

Antonio Fernando Menezes Freire  Ryo Matsumoto  Luiz Alberto Santos 《Marine and Petroleum Geology》2011,28(10):1967-1978

Integrated geological, geochemical, and geophysical exploration since 2004 has identified massive accumulation of gas hydrate associated with active methane seeps on the Umitaka Spur, located in the Joetsu Basin on the eastern margin of Japan Sea. Umitaka Spur is an asymmetric anticline formed along an incipient subduction zone that extends throughout the western side of the Japanese island-arc system. Seismic surveys recognized chimney structures that seem strongly controlled by a complex anticlinal axial fault system, and exhibit high seismic amplitudes with apparent pull-up structures, probably due to massive and dense accumulation of gas hydrate. Bottom simulating reflectors are widely developed, in particular within gas chimneys and in the gently dipping eastern flank of the anticline, where debris can store gas hydrates that may represent a potential natural gas resource. The axial fault system, the shape of the anticline, and the carrier beds induce thermogenic gas migration to the top of the structure, and supply gas to the gas hydrate stability zone. Gas reaching the seafloor produces strong seepages and giant plumes in the sea water column.  相似文献   

Numerical studies of methane production from Class 1 gas hydrate accumulations enhanced with carbon dioxide injection   总被引：2，自引：0，他引：2  

M.D. White  S.K. WurstnerB.P. McGrail 《Marine and Petroleum Geology》2011,28(2):546-560

Class 1 gas hydrate accumulations are characterized by a permeable hydrate-bearing interval overlying a permeable interval with mobile gas, sandwiched between two impermeable intervals. Depressurization-induced dissociation is currently the favored technology for producing gas from Class 1 gas hydrate accumulations. The depressurization production technology requires heat transfer from the surrounding environment to sustain dissociation as the temperature drops toward the hydrate equilibrium point and leaves the reservoir void of gas hydrate. Production of gas hydrate accumulations by exchanging carbon dioxide with methane in the clathrate structure has been demonstrated in laboratory experiments and proposed as a field-scale technology. The carbon dioxide exchange technology has the potential for yielding higher production rates and mechanically stabilizing the reservoir by maintaining hydrate saturations. We used numerical simulation to investigate the advantages and disadvantages of using carbon dioxide injection to enhance the production of methane from Class 1 gas hydrate accumulations. Numerical simulations in this study were primarily concerned with the mechanisms and approaches of carbon dioxide injection to investigate whether methane production could be enhanced through this approach. To avoid excessive simulation execution times, a five-spot well pattern with a 500-m well spacing was approximated using a two-dimensional domain having well boundaries on the vertical sides and impermeable boundaries on the horizontal sides. Impermeable over- and under burden were included to account for heat transfer into the production interval. Simulation results indicate that low injection pressures can be used to reduce secondary hydrate formation and that direct contact of injected carbon dioxide with the methane hydrate present in the formation is limited due to bypass through the higher permeability gas zone.  相似文献   

Pre- and post-drill comparison of the Mount Elbert gas hydrate prospect, Alaska North Slope     

M.W. Lee  W.F. AgenaT.S. Collett  T.L. Inks 《Marine and Petroleum Geology》2011,28(2):578-588

In 2006, the United States Geological Survey (USGS) completed a detailed analysis and interpretation of available 2-D and 3-D seismic data, along with seismic modeling and correlation with specially processed downhole well log data for identifying potential gas hydrate accumulations on the North Slope of Alaska. A methodology was developed for identifying sub-permafrost gas hydrate prospects within the gas hydrate stability zone in the Milne Point area. The study revealed a total of 14 gas hydrate prospects in this area.In order to validate the gas hydrate prospecting protocol of the USGS and to acquire critical reservoir data needed to develop a longer-term production testing program, a stratigraphic test well was drilled at the Mount Elbert prospect in the Milne Point area in early 2007. The drilling confirmed the presence of two prominent gas-hydrate-bearing units in the Mount Elbert prospect, and high quality well logs and core data were acquired. The post-drill results indicate pre-drill predictions of the reservoir thickness and the gas-hydrate saturations based on seismic and existing well data were 90% accurate for the upper unit (hydrate unit D) and 70% accurate for the lower unit (hydrate unit C), confirming the validity of the USGS approach to gas hydrate prospecting. The Mount Elbert prospect is the first gas hydrate accumulation on the North Slope of Alaska identified primarily on the basis of seismic attribute analysis and specially processed downhole log data. Post-drill well log data enabled a better constraint of the elastic model and the development of an improved approach to the gas hydrate prospecting using seismic attributes.  相似文献   

A margin-wide BSR gas hydrate assessment: Canada’s Atlantic margin     

David C. Mosher 《Marine and Petroleum Geology》2011,28(8):1540-1553

It is the intent of this paper to explore a significant extent of an entire passive continental margin for hydrate occurrence to understand hydrate modes of occurrence, preferred geologic settings and estimate potential volumes of methane. The presence of gas hydrates offshore of eastern Canada has long been inferred from estimated stability zone calculations, but little physical evidence has been offered. An extensive set of 2-D and 3-D, single and multi-channel seismic reflection data comprising in excess of 140,000 line-km was analyzed. Bottom simulating reflections (BSR) were unequivocally identified at seven sites, ranging between 250 and 445 m below the seafloor and in water depths of 620-2850 m. The combined area of the BSRs is 9311 km², which comprises a small proportion of the entire theoretical stability zone along the Canadian Atlantic margin (∼715,165 km²). The BSR within at least six of these sites lies in a sedimentary drift deposit or sediment wave field, indicating the likelihood of grain sorting and potential porosity and permeability (reservoir) development. Although there are a variety of conditions required to generate and recognize a BSR, one might assume that these sites offer the most potential for highest hydrate concentration and exploitation. Total hydrate in formation at the sites of recognized BSR’s is estimated at 17 to 190 × 10⁹ m³ or 0.28 to 3.12 × 10¹³ m³ of methane gas at STP. Although it has been shown that hydrate can exist without a BSR, the results from this regional study argue that conservative estimates of the global reserve of hydrate along continental margins are necessary.  相似文献   

Gas hydrate saturation from acoustic impedance and resistivity logs in the Shenhu area, South China Sea   总被引：4，自引：0，他引：4  

Xiujuan Wang  Shiguo Wu  Myung LeeYiqun Guo  Shengxiong YangJinqiang Liang 《Marine and Petroleum Geology》2011,28(9):1625-1633

During the China’s first gas hydrate drilling expedition -1 (GMGS-1), gas hydrate was discovered in layers ranging from 10 to 25 m above the base of gas hydrate stability zone in the Shenhu area, South China Sea. Water chemistry, electrical resistivity logs, and acoustic impedance were used to estimate gas hydrate saturations. Gas hydrate saturations estimated from the chloride concentrations range from 0 to 43% of the pore space. The higher gas hydrate saturations were present in the depth from 152 to 177 m at site SH7 and from 190 to 225 m at site SH2, respectively. Gas hydrate saturations estimated from the resistivity using Archie equation have similar trends to those from chloride concentrations. To examine the variability of gas hydrate saturations away from the wells, acoustic impedances calculated from the 3 D seismic data using constrained sparse inversion method were used. Well logs acquired at site SH7 were incorporated into the inversion by establishing a relation between the water-filled porosity, calculated using gas hydrate saturations estimated from the resistivity logs, and the acoustic impedance, calculated from density and velocity logs. Gas hydrate saturations estimated from acoustic impedance of seismic data are ∼10-23% of the pore space and are comparable to those estimated from the well logs. The uncertainties in estimated gas hydrate saturations from seismic acoustic impedances were mainly from uncertainties associated with inverted acoustic impedance, the empirical relation between the water-filled porosities and acoustic impedances, and assumed background resistivity.  相似文献   

High-resolution well-log derived dielectric properties of gas-hydrate-bearing sediments, Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope     

Y. Sun  D. GoldbergT. Collett  R. Hunter 《Marine and Petroleum Geology》2011,28(2):450-459

A dielectric logging tool, electromagnetic propagation tool (EPT), was deployed in 2007 in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert Well), North Slope, Alaska. The measured dielectric properties in the Mount Elbert well, combined with density log measurements, result in a vertical high-resolution (cm-scale) estimate of gas hydrate saturation. Two hydrate-bearing sand reservoirs about 20 m thick were identified using the EPT log and exhibited gas-hydrate saturation estimates ranging from 45% to 85%. In hydrate-bearing zones where variation of hole size and oil-based mud invasion are minimal, EPT-based gas hydrate saturation estimates on average agree well with lower vertical resolution estimates from the nuclear magnetic resonance logs; however, saturation and porosity estimates based on EPT logs are not reliable in intervals with substantial variations in borehole diameter and oil-based invasion.EPT log interpretation reveals many thin-bedded layers at various depths, both above and below the thick continuous hydrate occurrences, which range from 30-cm to about 1-m thick. Such thin layers are not indicated in other well logs, or from the visual observation of core, with the exception of the image log recorded by the oil-base microimager. We also observe that EPT dielectric measurements can be used to accurately detect fine-scale changes in lithology and pore fluid properties of hydrate-bearing sediments where variation of hole size is minimal. EPT measurements may thus provide high-resolution in-situ hydrate saturation estimates for comparison and calibration with laboratory analysis.  相似文献   

An installation system of deepwater risers by an S-lay vessel     

段梦兰  王懿  何宁  李丽娜  陈邦敏 《中国海洋工程》2011,25(1):139-148

Along with the consumption increase of the petroleum products,more countries have transferred their attentions to the offshore fields,especially the deepwater oil and gas reserves.For deepwater exploitation,the risers must be installed to act as the conduits connecting surface platforms to subsea facilities.In this paper,the typical risers sorted by different classes are introduced,and the correspondent installation methods are presented.By investigating the recent projects performed in the deepwater hot spots,and combining the challenges of HYSY201 for riser installation,a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of in the South China Sea.Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of in the South China Sea.  相似文献   

北京、郑州和深圳三城市空气中气溶胶单颗粒特征的扫描电镜分析   总被引：1，自引：0，他引：1  

赵承美  邵龙义  侯聪  幸娇萍  胡颖  王文华 《岩石矿物学杂志》2015,34(6):925-931

分别采集北京、深圳和郑州3个城市气溶胶样品,使用场发射扫锚电镜-能谱仪观察气溶胶单颗粒的显微形貌和元素组成,并利用图像分析系统对PM2.5的粒径进行了分析。结果表明,城市气溶胶单颗粒类型以矿物颗粒、烟尘和球形颗粒(飞灰和二次粒子)为主。对比3个城市气溶胶中不同颗粒类型数量百分比发现,矿物颗粒数量最多的城市是北京,飞灰和烟尘数量最多的城市是郑州,而规则矿物颗粒数量最多的城市是深圳。3个城市气溶胶单颗粒的数量-粒径分布均呈单峰分布。深圳气溶胶中颗粒物的粒径相对较小,其次为郑州、北京。3个城市气溶胶中颗粒物来源不同程度上都受到交通污染源影响,而燃煤源对北京和郑州气溶胶中颗粒物来源影响仍然不容忽视。  相似文献   

卵石地层的特殊性及其对基坑支护的影响分析     

刘伍  李海明 《城市地质》2015,(Z2)

主要从卵石地层的特征分类、特殊结构及场内施工条件3个方面,对基坑支护结构选型及施工工艺选择进行深入、系统的分析论证,力求使在卵石地层中的基坑支护设计方案更科学、经济,使施工方法、工艺更具可操作性。  相似文献