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Numerical Simulation for Accuracy of Velocity Analysis in Small-Scale High-Resolution Marine Multichannel Seismic Technology

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Journal of Ocean University of China 2017年第3期16卷 370-382页

作者： LUO Di CAI Feng WU Zhiqiang The key laboratory of gas hydrate Ministry of Land and ResourcesQingdao Institute of Marine Geology laboratory for Marine Mineral resources Qingdao National Laboratory for Marine Science and Technology

When used with large energy sparkers, marine multichannel small-scale high-resolution seismic detection technology has a high resolution, high-detection precision, a wide applicable range, and is very flexible. Positive results have been achieved in submarine geological research, particularly in the investigation of marine gas hydrates. However, the amount of traveltime difference information is reduced for the velocity analysis under conditions of a shorter spread length, thus leading to poorer focusing of the velocity spectrum energy group and a lower accuracy of the velocity analysis. It is thus currently debatable whether the velocity analysis accuracy of short-arrangement multichannel seismic detection technology is able to meet the requirements of practical application in natural gas hydrate exploration. Therefore, in this study the bottom boundary of gas hydrates(Bottom Simulating Reflector, BSR) is used to conduct numerical simulation to discuss the accuracy of the velocity analysis related to such technology. Results show that a higher dominant frequency and smaller sampling interval are not only able to improve the seismic resolution, but they also compensate for the defects of the short-arrangement, thereby improving the accuracy of the velocity analysis. In conclusion, the accuracy of the velocity analysis in this small-scale, high-resolution, multi-channel seismic detection technology meets the requirements of natural gas hydrate exploration.

关键词： small-scale high-resolution multichannel seismic velocity analysis accuracy gas hydrate

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Seismic rock physical modelling for gas hydrate-bearing sediments

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Science China Earth Sciences 2018年第9期61卷 1261-1278页

作者： Xinxin LIU Xingyao YIN Xiwu LUAN key laboratory of gas hydrate Ministry of Land and Resources Qingdao Institute of Marine Geology laboratory for Marine Mineral resources Qingdao National Laboratory for Marine Science and Technology School of Geosciences China University of Petroleum (East China)

There are ambiguities and uncertainties in the recognition of gas hydrate seismic reflections and in quantitative predictions of physical information of natural gas hydrate reservoirs from seismic data. Rock physical modelling is a bridge that transforms the seismic information of geophysical observations into physical information, but traditional rock physics models lack descriptions of reservoir micro-structures and pore-filling materials. Considering the mineral compositions and pore microstructures of gas hydrates, we built rock physical models for load-bearing and pore-filling gas hydrate-bearing sediments,describe the mineral compositions, pore connectivity and pore shape using effective media theory, calculated the shear properties of pore-filling gas hydrates using Patchy saturation theory and Generalized gassmann theory, and then revealed the quantitative relation between the elastic parameters and physical parameters for gas hydrate-bearing sediments. The numerical modelling results have shown that the ratios of P-wave and S-wave velocities decrease with hydrate saturation, the P-wave and S-wave velocities of load-bearing gas hydrate-bearing sediments are more sensitive to hydrate saturation, sensitivity is higher with narrower pores, and the ratios of the P-wave and S-wave velocities of pore-filling gas hydrate-bearing sediments are more sensitive to shear properties of hydrates at higher hydrate saturations. Theoretical analysis and practical application results showed that the rock physical models in this paper can be used to calculate the quantitative relation between macro elastic properties and micro physical properties of gas hydrate-bearing sediments, offer shear velocity information lacking in well logging, determine elastic parameters that have more effective indicating abilities, obtain physical parameters such as hydrate saturation and pore aspect ratios, and provide a theoretical basis and practical guidance for gas hydrate quantitative predic

关键词： gas hydrate Rock physical modelling Load-bearing gas hydrate Pore-filling gas hydrate Shear modulus Pore micro-structure Elastic parameter

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Influence of foraminifera on formation and occurrence characteristics of natural gas hydrates in fine-grained sediments from Shenhu area, South China Sea

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Science China Earth Sciences 2016年第11期59卷 2223-2230页

作者： LI ChengFeng HU GaoWei ZHANG Wei YE YuGuang LIU ChangLing LI Qing SUN JianYe key laboratory of gas hydrate Ministry of Land and Resources Qingdao Institute of Marine Geology laboratory for Marine Mineral resources Qingdao National Laboratory for Marine Science and Technology College of Information and Control Engineering China University of Petroleum

Marine gas hydrates accumulate primarily in coarse-grained, high-permeability layers; however, highly saturated natural gas hydrates have been discovered in the fine-grained sediments of Shenhu area, South China Sea(SCS). This may be explained by key factors, such as the great abundance of foraminifera shells. In this paper, by analyzing the SCS foraminifera structure and performing hydrate formation experiments in the foraminifera shells, the contribution of foraminifera to hydrate accumulation in the SCS was investigated from a microscopic point of view. Simulations of hydrate formation were carried out in both pure SCS foraminifera shells and the host sediments. Pore structures in typical foraminifera were studied by use of micro-focus X-ray computed tomography(CT) and scanning electron microscopy(SEM). hydrate growth and occurrence characteristics in the foraminifera shells were observed in-situ. The results showed that the presence of foraminifera significantly enhanced the effective porosity of the SCS sediments. Moreover, while the hydrates grew preferentially in the chambers of the coarse-grained foraminifera by adhering to the inner walls of the foraminifera shells, no apparent hydrate accumulation was observed in the fine-grained or argillaceous matrix. These findings provide a basis for further studies on the accumulation mechanism of hydrates and physical properties of hydrate reservoir in the South China Sea.

关键词： Shenhu area Foraminifera gas hydrate Occurrence characteristics X-ray computed tomography

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Features and Origin of Turbidity Current Sediment Waves in the Huatung Basin off the Eastern Taiwan Island

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Acta Geologica Sinica(English Edition) 2019年第4期93卷 1088-1096页

作者： LIU Jie SUN Meijing GAO Hongfang LI Xuejie key laboratory of gas hydrate Guangzhou Institute of Energy ConversionChinese Academy of SciencesGuangzhou 510640China key laboratory of Marine Mineral resources Ministry of Land and ResourcesGuangzhou Marine Geological SurveyGuangzhou 510075China

Based on numerous high-resolution seismic profiles,sediment waves and their distribution,morphological characteristics,internal structure,and potential origins were revealed in the eastern waters of *** sediment waves are located at the junction between the Taitung Canyon and other canyons in the *** wave length and the wave height of a single waveform ranged from 0.8 to 7.2 km and from 18 to 75 m,respectively(NE-SW direction).Sediment waves,located inside the bend of the Taitung Canyon,were characterized by an upward migration and showed mass transport deposits(MTDs)at the bottom,while the inner curve of the bend was subdivided into lower and upper wavy transition *** sediment waves on the outer curve of the bend were characterized by vertical accumulation,and there was no mass flow deposit at the *** to the geometry of the sediment waves,the calculated flow thicknesses across the entire wave field ranged from 196 to 356 m,and the current velocity ranged from 15 to 21 cm/*** morphological characteristics,the internal structure,and the distribution of sediment waves,as well as the numerical calculations,evidenced that these sediment waves had formed by turbidity *** development of the sediment wave field in eastern Taiwan was found to be similar to that in southwestern *** was the sedimentary response of the tectonic movement between 3 and^1 Ma which created the sedimentary systems where gravity flow processes *** current sediments settled in the place of less topographical constraints or overflowed in the bend section of the Taitung Canyon,which resulted in the formation of sediment wave fields.

关键词： Huatung Basin Taitung Canyon sediment wave turbidity current formation mechanism

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Forces Driving Changes in Cultivated land and Management Countermeasures in the Three Gorges Reservoir Area,China

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Journal of Mountain Science 2013年第1期10卷 149-162页

作者： CAO Yin-gui BAI Zhong-ke ZHOU Wei WANG Jing School of land Science and Technology China University of Geosciences key laboratory of land Reconsolidation and Rehabilitation Ministry of Land and Resources key laboratory of land Use Ministry of Land and Resources

The Three Gorges project accelerates economic development in the Three Gorges Reservoir *** paper aimed to investigate the distribution,changes and features of cultivated land in this area,analyze the forces driving the changes in cultivated land area,and propose the countermeasures for cultivated land *** matrix was used to analyze the features of cultivated land changes,and quantitative analysis and qualitative analysis were adopted to research the driving forces according to the features of cultivated land *** land in the Three Gorges Reservoir Area mainly lay to the northwest of the Yangtze River,especially the upper *** areas of cultivated land increased from 1996 to 1999,then decreased from 2000 to 2006,and finally increased again from 2007 to *** important forces driving changes in cultivated land included government policies,employment and food security,increasing construction land,agriculture structure adjustment,land rearrangement,*** cultivated land management,firstly,it is necessary to insist on the principle of cultivated land protection,standardize land exploitation and strictly restrict the transformation of cultivated land into non-farming ***,land rearrangement must be implemented,which can not only increase the area of the cultivated land,but also improve the quality of the cultivated ***,it is feasible to intensify eco-agriculture construction to increase the quantity and quality of cultivated ***,it is helpful to improve the traditional agriculture production methods to promote cultivated land ***,it is important to propagandize cultivated land protection and realize the enormous pressure of cultivated land shortage,making more people obligated to protect cultivated land.

关键词： land use change Driving force Management countermeasure Cultivated land Three Gorges Reservoir Area

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Investigation of shale gas microflow with the Lattice Boltzmann method

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Petroleum Science 2015年第1期12卷 96-103页

作者： Xiao-Ling Zhang Li-Zhi Xiao Long Guo Qing-Ming Xie State key laboratory of Petroleum resources and Prospecting China University of Petroleum key laboratory of Shale gas Exploration Ministry of Land and Resources Chongqing Institute of Geology and Mineral Resources

In contrast to conventional gas-bearing rocks, gas shale has extremely low permeability due to its nano- scale pore networks. Organic matter which is dispersed in the shale matrix makes gas flow characteristics more complex. The traditional Darcy＇s law is unable to estimate matrix permeability due to the particular flow mechanisms of shale gas. Transport mechanisms and influence factors are studied to describe gas transport in extremely tight shale. Then Lattice Boltzmann simulation is used to establish a way to estimate the matrix permeability numerically. The results show that net desorption, diffu- sion, and slip flow are very sensitive to the pore scale. Pore pressure also plays an important role in mass fluxes of gas. Temperature variations only cause small changes in mass fluxes. The Lattice Boltzmann method can be used to study the flow field in the micropore spaces and then provides numerical solutions even in complex pore structure models. Understanding the transport characteristics and establishing a way to estimate potential gas flow is very important to guide shale gas t＇eserve estimation and recovery schemes.

关键词： Shale gas Permeability Adsorption Desorption Diffusion Slip effect

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Coupled carbon and sulfur isotope behaviors and other geochemical perspectives into marine methane seepage

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Acta Oceanologica Sinica 2017年第6期36卷 12-22页

作者： LIU Lihua FU Shaoying ZHANG Mei GUAN Hongxiang WU Nengyou key laboratory of gas hydrate Guangzhou Institute of Energy ConversionChinese Academy of SciencesGuangzhou 510640China Guangzhou Marine Geological Survey Guangzhou 510760China the key laboratory of gas hydrate of ministry of land and resources Qingdao Institute of Marine GeologyQingdao 266071China laboratory for Marine Mineral resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266071China

Methane seepage is the signal of the deep hydrocarbon reservoir. The determination of seepage is significant to the exploration of petroleum, gas and gas hydrate. The seepage habits microbial and macrofaunal life which is fueled by the hydrocarbons, the metabolic byproducts facilitate the precipitation of authigenic minerals. The study of methane seepage is also important to understand the oceanographic condition and local ecosystem. The seepage could be active or quiescent at different times. The geophysical surveys and the geochemical determinations reveal the existence of seepage. Among these methods, only geochemical determination could expose message of the dormant seepages. The active seepage demonstrates high porewater methane concentration with rapid SO42- depleted, low HaS and dissolved inorganic carbon （DIC）, higher rates of sulfate reduction （SR） and anaerobic oxidation of methane （AOM）. The quiescent seepage typically develops authigenic carbonates with specific biomarkers, with extremely depleted 13C in gas, DIC and carbonates and with enriched 34S sulfate and depleted 34S pyrite. The origin of methane, minerals precipitation, the scenario of seepage and the possible method of immigration could be determined by the integration of solutes concentration, mineral composition and isotopic fractionation of carbon, sulfur. Numerical models with the integrated results provide useful insight into the nature and intensity of methane seepage occurring in the sediment and paleo- oceanographic conditions. Unfortunately, the intensive investigation of a specific area with dormant seep is still limit. Most seepage and modeling studies are site-specific and little attempt has been made to extrapolate the results to larger scales. Further research is thus needed to foster our understanding of the methane seepage.

关键词： marine seepage authigenic minerals carbon isotopes sulfur isotopes numerical simulation

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Remnants of an Powerful Ancient “Dynasty”:Material Cycle and Biomineralization in Modern Seafloor Hydrothermal System

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Acta Geologica Sinica(English Edition) 2016年第6期90卷 2287-2288页

作者： SUN Zhilei CAO Hong ZOU Mingliang ZHANG Xilin key laboratory of gas hydrate Ministry of Land and ResourcesQingdao Institute of Marine Geology laboratory for Marine Mineral resources Qingdao National Laboratory for Marine Science and Technology Changsha Uranium Geology Research institute China National Nuclear Corporation

The origin of ancient banded iron formation （BIF） has remained unclear for a long time. How the precipitation process occurred and what the environmental condition was have been widely discussed among scientists, because the period when the major BIFs deposited （-2.8 to 1.8Ga） is the same time when biosphere and atmosphere significantly changed. Based on the discovery of modern seafloor hydrothermal vents, it is possible that reductive environment controlled by vent system is related to the environment where BIF was deposited. According to matter source.

关键词： Remnants of an Powerful Ancient Dynasty Material Cycle and Biomineralization in Modern Seafloor Hydrothermal System

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Methane seepage intensities traced by sulfur isotopes of pyrite and gypsum in sediment from the Shenhu area,South China Sea

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Acta Oceanologica Sinica 2018年第7期37卷 20-27页

作者： ZHANG Mei LU Hongfeng GUAN Hongxiang LIU Lihua WU Daidai WU Nengyou key laboratory of gas hydrate Guangzhou Institute of Energy ConversionChinese Academy of SciencesGuangzhou 510640China Guangzhou Marine Geological Survey Guangzhou 510760China laboratory for Marine Mineral resources Qingdao National Laboratory for Marine Science and TechnologyQingdao 266061China key laboratory of gas hydrate Qingdao Institute of Marine GeologyMinistry of Land and ResourcesQingdao 266071China

The northern slope of the South China Sea is a gas-hydrate-bearing region related to a high deposition rate of organic-rich sediments co-occurring with intense methanogenesis in subseafloor *** oxidation of methane（AOM） coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and *** aggregates of pyrites and gypsums are observed between the depth of 667 and 850 cm below the seafloor（cmbsf） in the entire core sediment of HS328 from the northern South China *** pyrites are tubes consisting of framboidal cores and outer *** aggregates occur as rosettes and spheroids consisting of *** of them grow over pyrite,indicating that gypsum precipitation postdates pyrite *** sulfur isotopic values（δ^34 S） of pyrite vary greatly（from –46.6‰ to –12.3‰ V-CDT） and increase with ***,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction（OSR） and is influenced by AOM with *** relative high abundance and δ^34 S values of pyrite in sediments at depths from 580 to 810 cmbsf indicate that this interval is the location of a paleo-sulfate methane transition zone（SMTZ）.The sulfur isotopic composition of gypsum（from–25‰ to –20.7‰） is much lower than that of the seawater sulfate,indicating the existence of a 34 S-depletion source of sulfur species that most likely are products of the oxidation of pyrites formed in *** oxidation is controlled by ambient electron acceptors such as MnO2,iron（Ⅲ） and oxygen driven by the SMTZ location shift to great *** δ^34 S values of gypsum at greater depth are lower than those of the associated pyrite,revealing downward diffusion of 34 S-depleted sulfate from the mixture of oxidation of pyrite derived by OSR and the seawater *** sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formatio

关键词： pyrite tube authigenic gypsum sulfur isotopes methane seepage northern South China Sea

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Study of the Surface Morphology of gas hydrate

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Journal of Ocean University of China 2020年第2期19卷 331-338页

作者： SUN Jianye LI Chengfeng HAO Xiluo LIU Changling CHEN Qiang WANG Daigang The key laboratory of gas hydrate Ministry of Natural ResourcesQingdao Institute of Marine GeologyQingdao 266071China laboratory for Marine Mineral resources Pilot National Laboratory for Marine Science and TechnologyQingdao 266071China International Center for gas hydrate Peking UniversityBeijing 100871China

Study of the surface morphology of gas hydrate is of great importance in understanding its physical properties and *** order to investigate the surface morphology of different types(sI and sII)and occurrences(pore-filling and fracture-filling)of gas hydrate,both lab-synthesized and drilled-gas hydrate samples were measured using cryo-scanning electron microscopy(cryo-SEM).Results showed that the surface of s I hydrate was relatively smooth,and spongy nano-pores(200–400 nm)gradually occurred at the surface during continuous *** surface of sII hydrate was more compact,showing a tier-like *** occurred in quartz sand and usually filled the pores of the sediments and both hydrate and sediments were cemented with each *** observation of the gas hydrates collected from the South China Sea showed that the surface morphology and contact relation with sediments varied with hydrate *** instance,hydrates dispersed in sediments mainly filled the pores of the *** existence of microorganism shells,such as foraminifera,was beneficial to the formation of gas *** hydrate occurred as a massive or vein structure,it was easily distinguished from the surrounding *** surface of hydrate with massive or vein structure showed two distinct characters:one was dense and smooth,the other is porous(several to tens of micrometers in diameter).The occurrence of different hydrate morphologies was probably caused by the supplement rates of methane gas.

关键词： gas hydrate surface morphology cryo-SEM grain contacts

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