南海神狐海域沉积物自生黄铁矿和石膏S同位素特征及对甲烷渗漏强度的示踪   总被引：1，自引：1，他引：0  

张美  陆红锋  管红香  刘丽华  邬黛黛  吴能友 《海洋学报(英文版)》2018,37(7):20-27

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 environments.Anaerobic oxidation of methane(AOM) coupled with bacterial sulfate reduction results in the precipitation of solid phase minerals in seepage sediment,including pyrite and gypsum.Abundant 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 Sea.Most pyrites are tubes consisting of framboidal cores and outer crusts.Gypsum aggregates occur as rosettes and spheroids consisting of plates.Some of them grow over pyrite,indicating that gypsum precipitation postdates pyrite formation.The sulfur isotopic values(δ~(34) S) of pyrite vary greatly(from –46.6‰ to –12.3‰ V-CDT) and increase with depth.Thus,the pyrite in the shallow sediments resulted from organoclastic sulfate reduction(OSR) and is influenced by AOM with depth.The 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 OSR.Pyrite oxidation is controlled by ambient electron acceptors such as MnO_2,iron(Ⅲ) and oxygen driven by the SMTZ location shift to great depths.The 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 sulfate.These sulfates also lead to an increase of calcium ions from the dissolution of calcium carbonate mineral,which will be favor to the formation of gypsum.Overall,the mineralogy and sulfur isotopic composition of the pyrite and gypsum suggest variable redox conditions caused by reduced seepage intensities,and the pyrite and gypsum can be a recorder of the intensity evolution of methane seepage.  相似文献   

塔中4号油藏渗透率分布的非均质性及渗流方向研究     

陈青  闫长辉  蒋晓红 《地球科学与环境学报》2003,25(3):29-32

研究油藏内部油水渗流方向时,主要考虑渗透率影响,引入两个水平方向渗透率比、水平与垂向渗透率比参数来分析。前者反映样品所在储层平面上两个水平方向渗流能力的差异,后者反映样品所在储层水平与垂向渗流能力的差异,并经小柱样测试和全岩心测试两种方法确定两个参数。通过对塔中4号油藏CⅠ油组9口井2306个样品两种渗透率比值分布直方图分析,研究了CⅠ油组渗透率的非均质性及其渗流方向:CI油组储层在水平方向的渗流能力有很大差异,具有明显的方向性。储层垂向渗流能力明显小于水平方向的渗流能力。  相似文献   

三肇凹陷青山口组源岩生成油向下“倒灌”运移层位及其研究意义   总被引：14，自引：1，他引：13  

付广  王有功 《沉积学报》2008,26(2):355-360

为了研究三肇凹陷青山口组源岩生成的油向下“倒灌”运移层位,对油向下“倒灌”运移机制及条件进行了研究,得到三肇凹陷扶杨油层同时具备①青山口组源岩目前应具有足够大的超压;②存在连通青山口组源岩和扶杨油层的T2断裂2个条件,青山口组源岩生成的油能够在超压的作用下在嫩江组沉积末期、明水组沉积末期和古近系沉积末期通过T2断裂向下伏扶杨油层中“倒灌”运移。利用压力封闭原理,对三肇凹陷青山口组源岩生成的油向下“倒灌”运移距离进行了研究,得到三肇凹陷青山口组源岩生成的油向下“倒灌”运移距离一般大于500 m,而三肇凹陷扶杨油层地层厚度最大只有500 m,表明三肇凹陷青山口组源岩生成的油可以向下“倒灌”运移至整个扶杨油层的任何部位。目前三肇凹陷扶杨油层从上至下均含油,且已找到的油藏均分布于青山口组源岩生成的油能够向下“倒灌”运移分布范围内或附近,这表明青山口组源岩生成的油向下“倒灌”运移层位控制着油气富集层位,青山口组源岩生成的油向下“倒灌”运移分布范围控制着三肇凹陷扶杨油层油藏形成与分布范围。青山口组源岩生成的油向下“倒灌”运移分布范围及其附近应是三肇凹陷扶杨油层油下一步勘探的有利地区。  相似文献   

围垦区地下水位的控制及计算方法     

周理武  毛根海  宋建锋  陈观胜 《海洋学研究》2006,24(Z1):60-66

利用抽水井群和注水井群可以控制生态围垦区的地下水位.研究了潜水抽-注水井(群)耦合作用下浸润线的求解方法,利用势流理论和镜像原理,在假定含水层水平及土层渗透系数各向同性的条件下,推导出完整抽-注水井(群)耦合作用时浸润线的计算公式及非完整抽-注水井(群)耦合作用时浸润线的计算公式,还对潜水单个非完整抽水井及非完整抽-注水井群耦合作用时的解析解和数值解作了比较,结果表明,两者吻合得较好.同时还给出该理论用于地下水位控制中求解抽水量和注水量的方法等,对工程设计有实用价值.  相似文献   

An Experimental Study of Several Special Issues Regarding the Ice Force on Conical Structures     

SHI  Qing-zeng 《中国海洋工程》2002,16(4):561-568

The effect of the cone spacing of a conieal structure on the ice force is studied by model experiments. The ice force reduction coefficient presented in this paper expresses the relationship between the ice force and the arrangement of cones. The experiments prove that the mode of the ice failure before the boundary of upward-downward bending cone (UDBC) is crushing. A conclusion can also be drawn from the experiments that the ice force on the boundary of UDBC is by far less than that on a vertical pile with the same diameter. Moreover, the ice force frequencies on upright and inve-rted cones are obtained under the field condition of the platform JZ20-2, respectively. The results show that the alterna-tion of the ice force on UDBC can hardly induce resonance of platform JZ20-2.  相似文献   

Salt Diapirs, Salt Brine Seeps, Pockmarks and Surficial Sediment Creep and Slides in the Canary Channel off NW Africa     

J. Acosta  E. Uchupi  A. Muñoz  P. Herranz  C. Palomo  M. Ballesteros 《Marine Geophysical Researches》2003,24(1-2):41-57

Circular to elliptical mounds in the Canary Channel with reliefs of 75 to 375 m and diameters of 4 to 8 km partially surrounded by moats with reliefs of 25 to 75 m, were formed by piercement of the seafloor by Mesozoic evaporites. Several long gullies, < 1km wide, with abrupt terminations and pockmarks associated with these mounds were probably eroded by dense brine and hydrocarbon seeps. The salt brines that eroded the gullies were formed where salt diapirs intersect the seafloor, or in the subsurface by circulating ground water heated by igneous activity along the Canary Ridge. If the brines originated in the subsurface they reached the seafloor along faults. Displacement of the surficial sediments by sliding and creep is probably the result of the expulsion of hydrocarbons and/or vertical motion of the Mesozoic evaporites. Microtopographic features along or near the east flank of the Canary Ridge are the creation of uplift of the ridge, hydrothermal activity, mass wasting processes and turbidity currents.  相似文献   

Bottom Simulating Reflector and Gas Seepage in Okinawa Trough： Evidence of Gas Hydrate in an Active Back-Arc Basin     

栾锡武  Kelin  Wang  Roy  Hyndman  Eleanor  Willoughby 《中国地质大学学报(英文版)》2008,19(2):152-161

To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector (BSR) occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural "anomalies" are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation:to help gather enough methane into a small area and to modulate the thermal regime.  相似文献   

IODP 311航次底栖有孔虫碳稳定同位素对天然气水合物地质系统的指示     

李清  王家生  王晓芹  陈祈  陈洪仁 《地球科学进展》2008,23(11):1161-1166

为了探索海洋天然气水合物背景下有孔虫特征的响应,对综合大洋钻探计划(IODP) 311航次岩芯沉积物中底栖有孔虫Uvigerina peregrina和Bulimina mexicana进行了初步研究。通过对冷泉站位U1328和毗邻的非冷泉站位U1327沉积物中底栖有孔虫Uvigerina peregrina和Bulimina mexicana的显微形貌特征和碳、氧稳定同位素测试等,证实有孔虫壳体未受到后期成岩作用的改造和自生碳酸盐岩的交代影响,有孔虫壳体的碳稳定同位素呈现明显的负偏。其中U1327站位中U.peregrina δ¹³C为-0.67‰～-2.75‰（PDB）,B.mexicana δ¹³C为-0.51‰～-1.52‰（PDB）;U1328站位中U.peregrina δ¹³C为 -0.72‰～-2.71‰（PDB）,B.mexicanaδ¹³C为 -0.58‰～-1.45‰（PDB）。底栖有孔虫壳体的碳稳定同位素负偏成因可能与水合物不稳定分解释放的甲烷厌氧氧化作用和食物源有关,因而可较好地指示海底天然气水合物系统地质背景。  相似文献   

The Role of Fracture Structure in Leachate Pollution at Landfills： A Case Study of a Landfill in Chongqing City     

LUO Yunju  LIU Dongyan  LI Xiulan  ZHU Zhengwei 《《地质学报》英文版》2008,82(5)

This paper studies a landfill where there are three faults running through.As serious pollution has occurred to the geological environment,the landfill is to be closed up and renovated.The paper aims to explore the role of fracture structure in leachate pollution at the landfill.The research was carried out in several stages.First,mathematical models of the pre-renovation landfill with three faults running through and the landfill after renovation were established.And then,the boundary conditions and parameters of the two mathematical models were determined.The groundwater level of the landfills was simulated in order to modify the two mathematical models.As a result,a feasible mathematical model was achieved.Based on this model,a comparison was made of the COD concentration variations in the inside leachate and outside leachate between the two landfills. Accordingly,the impacts of the fracture structure on the pollution of leachate at the landfills could be identified.The study results show that while faults contribute to the migration of leachate,they also serve as a confluence of leachate,thus further deteriorating the environment.The COD concentrations of the inside leachate and the outside leacbate of the pre-renovation landfill are respectively 800 mg/L and 220 mg/L higher than those of the post.renovation landfill.Therefore,measures must be taken to handle the leachate seepage in areas where there are faults as well as the neighboring areas so as to get the environmental pollution under control.  相似文献   

The Role of Fracture Structure in Leachate Pollution at Landfills: A Case Study of a Landfill in Chongqing City     

LUO Yunju  LIU Dongyan  LI Xiulan  ZHU Zhengwei 《《地质学报》英文版》2008,82(5):1020-1026

This paper studies a landfill where there are three faults running through. As serious pollution has occurred to the geological environment, the landfill is to be closed up and renovated. The paper aims to explore the role of fracture structure in leachate pollution at the landfill. The research was carried out in several stages. First, mathematical models of the pre-renovation landfill with three faults running through and the landfill after renovation were established. And then, the boundary conditions and parameters of the two mathematical models were determined. The groundwater level of the landfills was simulated in order to modify the two mathematical models. As a result, a feasible mathematical model was achieved. Based on this model, a comparison was made of the COD concentration variations in the inside leachate and outside leachate between the two landfills. Accordingly, the impacts of the fracture structure on the pollution of leachate at the landfills could be identified. The study results show that while faults contribute to the migration of ieachate, they also serve as a confluence of leachate, thus further deteriorating the environment. The COD concentrations of the inside leachate and the outside leachate of the pre-renovation landfill are respectively 800 mg/L and 220 mg/L higher than those of the post-renovation landfill. Therefore, measures must be taken to handle the ieachate seepage in areas where there are faults as well as the neighboring areas so as to get the environmental pollution under control.  相似文献