Sub-seismic scale fracture pattern and in situ permeability data in the chalk atop of the Krempe salt ridge at Lägerdorf, NW Germany: Inferences on synfolding stress field evolution and its impact on fracture connectivity     

Fabrizio Storti  Fabrizio BalsamoFederico Cappanera  Giambattista Tosi 《Marine and Petroleum Geology》2011,28(7):1315-1332

Chalk is exposed in the Heidestrasse quarry at Lägerdorf, at the top of the NE-SW trending Krempe salt ridge. Structural data indicate the presence of two joint sets, striking almost parallel and perpendicular to the salt ridge, respectively, and of a set of conjugate extensional faults and fault zones striking NW-SE, i.e. almost perpendicular to the salt ridge. Within the overall NW-SE trend of joints and faults, strike variations occur from the massive chalk exposed in the lower half of the quarry, to the overlying layered chalk. A large variability characterizes the normalized spacing of both joint sets, which does not show any clear trend with layer dip. In situ measurements indicate that the cross-sectional permeability of tight joints increases 1-2 orders of magnitude with respect to the undeformed chalk. We propose that joint and fault azimuthal variability resulted from changes through time of the stress ellipsoid at the top of the salt ridge, while joint spacing variability is associated with the weak mechanical influence of bedding in chalk. Azimuthal variability improves fracture connectivity and, hence, permeability and fluid flow.  相似文献   

Characteristics of the boundary layer at the bottom of a solitary wave     

Giovanna Vittori  Paolo Blondeaux 《Coastal Engineering》2011

The results of direct numerical simulations of the boundary layer generated at the bottom of a solitary wave are described. The numerical results, which agree with the laboratory measurements of Sumer et al. (2010) show that the flow regime in the boundary layer can be laminar, laminar with coherent vortices and turbulent. The average velocity and bottom shear stress are computed and the results obtained show that the logarithmic law can approximate the velocity profile only in a restricted range of the parameters and at particular phases of the wave cycle. Moreover, the maximum value of the bottom shear stress is found to depend on the dimensionless wave height only, while the minimum (negative) value depends also on the dimensionless boundary layer thickness. Diagrams and simple formulae are proposed to evaluate the minimum and maximum bottom shear stresses and their phase shift with respect to the wave crest.  相似文献   

AVO与流体替换相结合识别深层Ⅰ类气藏     

涂齐催  刘江  崔树果  霍凤斌 《海洋地质译丛》2011,(2):25-28

传统的“亮点”技术适合检测Ⅲ类AVO含气异常,对于中、深层含气砂岩表现出来的Ⅰ类AVO现象无法识别。利用AVO技术,结合流体替换,寻找差异,运用G属性体,可以有效识别深层Ⅰ类AVO含气砂岩,利用这种方法预测了某油气田a主力气藏的分布。预测结果得到B井证实。  相似文献   

民勤大气边界层特征与沙尘天气的气候学关系研究   总被引：4，自引：0，他引：4  

李岩瑛  张强  薛新玲  王荣基 《中国沙漠》2011,30(3):757-764

 为了更好地理解西北干旱区大气混合层(ML)厚度的变化特征及其对当地沙尘气候形成的影响, 利用民勤2006—2008年3—6月逐日08时和20时探空资料、降水和日最高气温,计算和分析了最大混合层厚度、逆温层特征和垂直风场及其对沙尘气候形成的影响。结果表明,民勤沙尘天气的大气边界层有显著的昼夜变化,白天厚、逆温强而多;沙尘天气的最大混合层厚度在2 600 m左右,介于无降水与有降水天气之间;扬沙主要由锋面中的冷空气引起,而沙尘暴主要由低层风场的剧烈扰动和500 m以上高层冷锋入侵引起。沙尘暴发生前近地面风场有明显的扰动,沙尘暴发生时在500 hPa以下有显著的冷空气活动,白天较强。能见度小于100 m的强沙尘暴夜间风速大,冷空气较强。  相似文献   

Structural evolution of a salt-cored,domed, reactivated fault complex,Jebel Madar,Oman     

《Journal of Structural Geology》2013

Fault and fracture patterns associated with domal structures are observed around the world both at outcrop and in the subsurface. However, the structural evolution of domes and the influence of previous fault and fracture sets are not yet fully understood. This study provides the first structural evolution analysis of Jebel Madar, a domal outcrop in the Adam Foothills of Northern Oman, and evaluates the role of multiple local tectonic events and the associated salt diapirism on fracture and fault distribution pattern development of a salt-cored domal outcrop.Analyses at Jebel Madar suggest that three local tectonic events with different stress regimes that are tentatively linked to three regional tectonic events resulted in a salt-cored, domed, reactivated fault complex: 1) initial dome-formation and NE–SW oriented mode 1 opening fractures and subsequent grabens; 2) E–W oriented dextral strike-slip faulting; and 3) reactivation and inversion of faults, and final dome formation. Salt emplacement is associated with the first and last tectonic events.This integrated study highlights the complicated evolution of fault and fracture distribution patterns at a salt-cored dome. Caution is therefore required in interpretation of similar structural patterns on top of and around salt-cored domes.  相似文献   

Illite/smectite transformation in detrital glaucony during burial diagenesis of sandstone: A study from Siri Canyon – Danish North Sea     

AFSOON M. KAZEROUNI  METTE L. K. POULSEN  HENRIK FRIIS  JOHAN B. SVENDSEN  JENS P. V. HANSEN 《Sedimentology》2013,60(3):679-692

Detrital glaucony in the Palaeogene glauconitic sandstones in Siri Canyon, Danish North Sea, has been analysed from 15 exploration wells by X‐ray diffraction, electron microprobe and scanning electron microscopy. These sandstones consist of mixed‐layer illite/smectite and have a large variability in chemical composition and structure. In the most shallow wells (ca 1700 m), the glaucony is rich in Fe and consists of mixed‐layer illite/smectite with random‐interstratification (R = 0). In the depth interval from 1700 to 2000 m, the composition changes as Si is incorporated. The structure changes to ordered R = 1. Further increase in burial leads to the loss of Fe. Ordered R = 3 mixed‐layer illite/smectite is recognized from burial depths of 2200 m. The proportion of illite in illite/smectite mixed layers increases only slightly with depth and temperature. Although the structural changes generally are associated with chemical changes, they can also take place isochemically when the detrital glaucony is tightly embedded in earlier cement, which prevented chemical exchange. The glaucony transformation in the Siri Canyon sandstones partly reflects a supply of Si and partly significant loss of Fe. Thus, the glaucony transformation relates to the general diagenesis of the host sandstone. These sandstones are cemented by microquartz at an early stage, followed by precipitation of Fe‐rich grain‐coating berthierine or chlorite.  相似文献   

冲断构造带深层变形的空间分布规律——以库车坳陷克拉苏构造带为例   总被引：1，自引：0，他引：1       下载免费PDF全文

李本亮  陈竹新  谢会文  雷刚林  张朝军  边海光 《地质科学》2013,(1):167-175

传统上认为前陆冲断带内部的背斜构造具有"成排成带分段"的特征,在表观认识和宏观尺度上讲,容易理解这一特征,并且通过"成排成带分段"的解剖,直接为含油气区带评价和地震解释方案的落实提供指导作用。随着前陆冲断带深层结构的精细解剖和三维空间内构造变形的准确刻画,发现前陆冲断带深层构造变形的分布并非成排成带分段的特征,褶皱构造的发育与分布明显受前陆冲断构造位移量及各个断层位移量的大小所控制,各个断层控制的逆冲岩席在垂向上相互叠置、侧向上交叉对接、走向上错落有致, 3D立体空间内由多个次级弧形体组成鳞片状分布。本文以中国天然气勘探最为成功、勘探资料最为详实的库车坳陷克拉苏构造带为例,通过地震剖面精细构造解释,揭示出构造变形的运动学特征及其构造位移量在传播过程中的分异和转换,进而控制冲断带内部构造岩席的生长发育和空间展布特征,并在3D立体空间内揭示冲断岩席受构造位移量的控制而成鳞片状分布的规律,控制这一分布规律的主控因素是冲断构造位移量与冲断岩席长度之间定量的几何关系。这一认识提升了油气藏评价和构造圈闭描述的精度。  相似文献   

Elasto-viscoplastic finite element study of the effect of degradation on bearing capacity of footing on clay ground     

《Geomechanics and Geoengineering》2013,8(4):235-251

The bearing capacity of footing has been studied by both conventional and numerical methods by many researchers. However, degradation of the microstructure of material, that is, a change in the microstructure of the soil, has not been adequately taken into account. Degradation of microstructure causes strain softening of materials and it leads to strain localization such as shear bands and slip bands. From an engineering point of view the strain localization is crucial because it is a precursor of failure. In the present study, finite element analyses of the bearing capacity of a shallow foundation on homogeneous and inhomogeneous saturated clay strata have been conducted using an elasto-viscoplastic soil constitutive model of microstructure change. A series of analyses of footing on clay deposit with different microstructure parameters have been carried out. Numerical results show that strain localization can be predicted during the loading of rigid footing on highly structured soil and strain localization affects the footing–soil interaction. The effects of footing roughness on the failure mechanism are also discussed in the study.  相似文献   

特厚砂土层条件下的开采沉陷规律研究     

朱占荣  陈利平  郝延锦 《中国煤炭地质》2013,(8)

在分析榆树湾煤矿地表移动观测资料的基础上,研究了特厚砂土层条件下的厚煤层开采的地表移动变形规律与特征。揭示了特厚砂土层、薄基岩及大采厚等特殊因素对地表沉陷规律的影响,获得了特厚砂土层开采条件下的地表移动变形特征,研究成果将对榆林煤矿后续的安全合理开采、保安煤柱的留设、环境治理与保护等具有重要的实际意义。  相似文献   

Artificial neural network model for prediction of rock properties from sound level produced during drilling     

《Geomechanics and Geoengineering》2013,8(1):53-61

In many rock engineering applications such as foundations, slopes and tunnels, the intact rock properties are not actually determined by laboratory tests, due to the requirements of high quality core samples and sophisticated test equipments. Thus, predicting the rock properties by using empirical equations has been an attractive research topic relating to rock engineering practice for many years. Soft computing techniques are now being used as alternative statistical tools. In this study, artificial neural network models were developed to predict the rock properties of the intact rock, by using sound level produced during rock drilling. A database of 832 datasets, including drill bit diameter, drill bit speed, penetration rate of the drill bit and equivalent sound level (L_eq) produced during drilling for input parameters, and uniaxial compressive strength (UCS), Schmidt rebound number (SRN), dry density (ρ), P-wave velocity (V_p), tensile strength (TS), modulus of elasticity (E) and percentage porosity (n) of intact rock for output, was established. The constructed models were checked using various prediction performance indices. Goodness of the fit measures revealed that recommended ANN model fitted the data as accurately as experimental results, indicating the usefulness of artificial neural networks in predicting rock properties.  相似文献