Thresholds of intrabed flow and other interactions of turbidity currents with soft muddy substrates          下载免费PDF全文

Jaco H. Baas  Rafael Manica  Eduardo Puhl  Ana Luiza de Oliveira Borges 《Sedimentology》2016,63(7):2002-2036

Controlled laboratory experiments reveal that the lower part of turbidity currents has the ability to enter fluid mud substrates, if the bed shear stress is higher than the yield stress of the fluid mud and the density of the turbidity current is higher than the density of the substrate. Upon entering the substrate, the turbidity current either induces mixing between flow‐derived sediment and substrate sediment, or it forms a stable horizontal flow front inside the fluid mud. Such ‘intrabed’ flow is surrounded by plastically deformed mud; otherwise it resembles the front of a ‘bottom‐hugging’ turbidity current. The ‘suprabed’ portion of the turbidity current, i.e. the upper part of the flow that does not enter the substrate, is typically separated from the intrabed flow by a long horizontal layer of mud which originates from the mud that is swept over the top of the intrabed flow and then incorporated into the flow. The intrabed flow and the mixing mechanism are specific types of interaction between turbidity currents and muddy substrates that are part of a larger group of interactions, which also include bypass, deposition, erosion and soft sediment deformation. A classification scheme for these types of interactions is proposed, based on an excess bed shear stress parameter, which includes the difference in the bed shear stress imposed by the flow and the yield stress of the substrate and an excess density parameter, which relies on the density difference between the flow and the substrate. Based on this classification scheme, as well as on the sedimentological properties of the laboratory deposits, an existing facies model for intrabed turbidites is extended to the other types of interaction involving soft muddy substrates. The physical threshold of flow‐substrate mixing versus stable intrabed flow is defined using the gradient Richardson number, and this method is validated successfully with the laboratory data. The gradient Richardson number is also used to verify that stable intrabed flow is possible in natural turbidity currents, and to determine under which conditions intrabed flow is likely to be unstable. It appears that intrabed flow is likely only in natural turbidity currents with flow velocities well below ca 3·5 m s^?1, although a wider range of flows is capable of entering fluid muds. Below this threshold velocity, intrabed flow is stable only at high‐density gradients and low‐velocity gradients across the upper boundary of the turbidity current. Finally, the gradient Richardson number is used as a scaling parameter to set the flow velocity limits of a natural turbidity current that formed an inferred intrabed turbidite in the deep‐marine Aberystwyth Grits Group, West Wales, United Kingdom.  相似文献   

基于热模拟实验的富有机质泥页岩成岩作用及演化特征   总被引：1，自引：0，他引：1  

栾国强  董春梅  马存飞  林承焰  张津营  吕夏霏  Muhammad Aleem Zahid 《沉积学报》2016,34(6):1208-1216

富有机质泥页岩蕴含丰富的油气资源,但成岩研究基础薄弱,已成为制约页岩油气勘探开发进程的重要因素。通过开展成岩热模拟实验,结合扫描电镜观察、流体成分测试及有机酸测试等实验测试手段,全面描述实验过程中所发生的水-岩化学反应,试图揭示泥页岩成岩过程及成岩演化规律。研究结果显示,有机质热演化过程中存在一个较宽的有机酸生成窗口,对孔隙流体性质具有重要影响;长石和方解石存在接力溶蚀现象,长石溶蚀高峰过后紧接着出现方解石溶蚀高峰,但方解石溶蚀窗较窄,此后出现方解石重新沉淀结晶;黏土矿物转化及长石的溶蚀过程中会产生大量自生微晶石英,成链状或簇状胶结泥页岩骨架。泥页岩地层作为一个相对封闭体系,各类成岩作用之间相互关联,相互影响,构成错综复杂的成岩体系,进一步增加其成岩作用研究难度。  相似文献   

Reservoir Characteristics of Lacustrine Shale and Marine Shale: Examples from the Songliao Basin, Bohai Bay Basin and Qiannan Depression     

WANG Min  LU Shuangfang  WANG Zhiwei  LIU Yang  HUANG Wenbiao  CHEN Fangwen  XU Xingyou  LI Zheng  LI Jijun 《《地质学报》英文版》2016,90(3):1024-1038

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Shale Gas Formation and Occurrence in China: An Overview of the Current Status and Future Potential     

ZOU Caineng  YANG Zhi  PAN Songqi  CHEN Yanyan  LIN Senhu  HUANG Jinliang  WU Songtao  DONG Dazhong  WANG Shufang  LIANG Feng  SUN Shash  HUANG Yong  WENG Dingwei 《《地质学报》英文版》2016,90(4):1249-1283

Shale gas is one of the most promising unconventional resources both in China and abroad. It is known as a form of self-contained source-reservoir system with large and continuous dimensions. Through years of considerable exploration efforts, China has identified three large shale gas fields in the Fuling, Changning and Weiyuan areas of the Sichuan Basin, and has announced more than 540 billion m~3 of proven shale gas reserves in marine shale systems. The geological theories for shale gas development have progressed rapidly in China as well. For example, the new depositional patterns have been introduced for deciphering the paleogeography and sedimentary systems of the Wufeng shale and Longmaxi shale in the Sichuan Basin. The shale gas storage mechanism has been widely accepted as differing from conventional natural gas in that it is adsorbed on organic matter or a mineral surface or occurs as free gas trapped in pores and fractures of the shale. Significant advances in the techniques of microstructural characterization have provided new insights on how gas molecules are stored in micro- and nano-scale porous shales. Furthermore, newly-developed concepts and practices in the petroleum industry, such as hydraulic fracturing, microseismic monitoring and multiwell horizontal drilling, have made the production of this unevenly distributed but promising unconventional natural gas a reality. China has 10–36 trillion m~3 of promising shale gas among the world's whole predicted technically recoverable reserves of 206.6 trillion m~3. China is on the way to achieving its goal of an annual yield of 30–50 billion m~3 by launching more trials within shale gas projects.  相似文献   

A Review of the Bentong-Raub Suture vis-à-vis New Insight of the Tectonic Evolution of Malay Peninsula, South East Asia     

Aftab Alam KHAN  Mustaffa Kamal SHUIB 《《地质学报》英文版》2016,90(5):1865-1886

As a milestone of the entire energy industry, unconventional resources have inevitably swept the world in the last decade, and will certainly dominate the global oil and gas industry in the near future. Eventually, the “unconventional” will become “conventional”. Along with the rapid development, however, some issues have emerged, which are closely related to the viability of unconventional resources development. Under the current circumstances of low crude oil and gas price, coupled with the prominent environmental concerns, the arguments about the development and production of unconventional resources have been recently heated up. This work introduced the full-blown aspects of unconventional resources especially shale reservoirs, by discussing their concepts and definitions, reviewing the shale gas and shale oil development history and necessity, analyzing the shale plays’ geology and petroleum systems with respects to key hydrocarbon accumulation elements and mechanisms, and summarizing the technology resolution. This study also discussed the relevant key issues, including significant estimation uncertainty of technically recoverable resources, the equivocal understanding of complex geology preventing the production and technologies implementation optimization, the difficulties of experiences and technologies global expanding, and the corresponding risks and uncertainties. In addition, based on the latest production and exploration data, the future perspective of the unconventional resources was depicted from global unconventional resources assessments, technology development, and limitations constraining the development.  相似文献   

河南义马地区页岩气储层孔隙非均质性     

张晓波  左兆喜  张超  司庆红  张义 《地球学报》2016,37(3):340-348

运用高压压汞、液氮吸附及渗透率测试等实验,利用极差、突进系数、变异系数等参数,表征煤系页岩孔渗特征及孔隙层间非均质性,分析孔隙层间非均质性主控因素。结果表明:河南义马地区上、下石盒子组泥页岩微孔与小孔较为发育,山西组大孔较为发育,分别提供了气体吸附附着面积和储存运移空间;上石盒子组孔容与孔径相对偏差最小,孔隙分布均匀,山西组比表面积相对偏差最小,表面积分布均匀;随围压增大,渗透率不断降低,且满足负指数相关关系;渗透率级差、突进系数和变异系数显示下石盒子组渗透率非均质性较弱,山西组渗透率非均质性很弱,更易于压裂开发。非均质性宏观上主要受沉积物质组成和构造改造作用影响,微观上受成岩演化影响。  相似文献   

昭通示范区黄金坝气田五峰—龙马溪组页岩气储层地质特征   总被引：5，自引：5，他引：0       下载免费PDF全文

伍坤宇  张廷山  杨洋  梁兴  周松源  张朝 《中国地质》2016,(1):275-287

昭通国家级页岩气示范区黄金坝气田是继礁石坝和长宁—威远之后中国又一个在页岩气勘探、开发领域实现重大突破的地区,为了系统地展示黄金坝气田页岩气资源富集的储层条件,为未来的勘探工作提供参考,以五峰—龙马溪组页岩气储层为研究对象,从区域地质条件、储层岩石学、物性和地球化学4个方面对该页岩气储层进行了综合研究。结果表明稳定的区域构造和良好的顶底板条件是黄金坝地区页岩气资源富集的关键,良好的保存条件使储层维持了较高的压力(压力系数1);较高的孔隙度(平均4%)和TOC含量(目的层2%)提供了良好的储集空间,使储层具有较高的含气量(1.35~3.48 cm3/g,平均2.50 cm3/g);天然气地球化学数据表明,区内天然气主要成分为CH4(97%),其次还含有少量的C2H6、C3H8和CO2;天然气同位素数据表明烃类C同位素组成发生了倒转,表明储层具有良好的封闭性。但储层孔隙系统较为复杂,且非均质性极强,从而导致渗透率较低,在储层改造施工过程中应予以充分考虑。总体上,黄金坝气田具有较好的开发前景,生产测试表明,区内直井压裂产量为0.5×104~3.5×104m3/d/井,水平井压裂产量可达12×104~40×104m3/d/井。  相似文献   

贵州织金下寒武统黑色页岩矿物岩石成分及资源利用特征     

王沙  张杰 《岩石矿物学杂志》2016,35(3):543-552

通过野外采样、化学分析、电子探针(EPMA)和X射线衍射(XRD)分析等手段,研究了贵州织金地区黑色页岩矿物成分、化学组分、微量元素、稀土元素特征。研究区矿样化学成分以SiO_2和Al_2O_3为主,且具有高K低Na的特征。电子探针和X射线衍射分析表明,研究区黑色页岩主要矿物组成有石英、粘土矿物、白云石及黄铁矿等。织金黑色页岩中Pb、Ni、U、V、Cr等金属元素存在不同程度的富集,稀土元素总量为153.2×10~(-6)~224.89×10~(-6),属轻稀土元素富集型。同时从多金属层、页岩气、页岩提钾及近底部含磷铀矿资源等方面讨论了织金黑色页岩资源化利用。织金黑色页岩多金属层含有Mo、V、Ni、Ag及U等多金属元素,具综合利用价值;其中有机碳含量达到页岩气开发大于2%的条件,可进一步开展研究;页岩中伊利石含量较多,可提取黑色页岩中的钾制备含钾复合肥;黑色页岩底部与磷矿层接触带产出磷铀矿,主要为胶状磷铀矿,接触带可作为铀矿找矿的标志层。  相似文献   

新疆博格达山北麓白杨河剖面页岩地球化学特征及其地质意义     

赵仕华 《岩石矿物学杂志》2016,35(2):255-264

通过博格达山北麓白杨河剖面芦草沟组页岩的地球化学特征的综合研究,讨论了芦草沟组页岩的元素富集特征和沉积环境以及源区物源特征和构造背景。结果表明:1研究区页岩P元素极为富集,这受控于页岩中凝灰质火山灰夹层的广泛发育;2对比于世界页岩微量元素分布,白杨河页岩相对富集Li、B、Pr、Tb、Dy、Ho、Er、Tm和Lu元素,其他元素相对亏损;3白杨河剖面页岩地化参数揭示芦草沟组自下而上气候由温湿向干热转变,进而引起水体由淡水向咸水的转变和还原程度的进一步加强;4物源区遭受低级-中等风化程度,物源类型主要为长英质火成岩,其次为铁镁质火成岩;5物源区大地构造背景以大陆岛弧-活动大陆边缘构造背景为主。  相似文献   

济阳坳陷古近系泥页岩成因相划分     

郝运轻  王朴  刘惠民  谢忠怀  毕彩芹  滕建彬  方正伟 《岩石矿物学杂志》2016,35(6):981-990

系统岩心观察和高密度薄片鉴定等分析测试资料研究结果显示,济阳坳陷沙三下-沙四上泥页岩成分组成及构造类型主要受沉积作用控制,岩石结构特征主要受成岩作用控制。根据泥页岩中方解石成因及重结晶程度,结合岩石成分及构造特征,将济阳坳陷沙三下-沙四上泥页岩划分为沉积主控型、沉积-成岩双控型及成岩主控型三大成因相。沉积主控型分布最为广泛,岩相类型多样,构造特征反映成因环境;沉积-成岩双控型主要见于纹层状岩相,由泥质纹层与显晶粒状方解石纹层互层构成;成岩主控型以柱状、柱纤状方解石垂直层面呈脉状、透镜状产出为特征。成岩主控型和沉积-成岩双控型泥页岩与页岩油气关系密切,是重要的有利成因相类型。  相似文献