深地震反射剖面揭示嫩江断裂带中段的深部几何形态与地壳形变

嫩江断裂带对探讨松辽盆地的演化、 与大兴安岭的盆山耦合关系以及兴安地块与松嫩地块的归属问题具有重要研究意义。本文利用深地震反射剖面, 揭示了嫩江断裂带中段的深部几何形态, 表明它目前呈花状构造样式; 它也并非松辽盆地内部的拆离断层, 而是一条超壳断裂, 控制了大兴安岭的物质东移和松辽盆地的中生代沉积; 现今的嫩江断裂带同晚古生代兴安地块与松嫩地块拼合的嫩江构造拼贴带并没有继承性关系; 莫霍面可能在后期的演化过程中扮演了滑脱层的作用, 致使向西俯冲的地幔体向东位移。     

Experimental investigations on the geometry and connectivity of pore space in organic-rich Wufeng and Longmaxi shales

The nano-scale pore systems of organic-rich shale reservoirs were investigated from Upper Ordovician Wufeng and Lower Silurian Longmaxi Formations in southeast Sichuan Basin. These two formations are the most important target plays of shale gas development in China. The purpose of this article is to assess the geometry and connectivity of multi-scale pore systems, and to reveal the nature and complexity of pore structure for these over-mature gas shales. To achieve these objective, total organic carbon, mineralogy, image analyses by focused ion beam-SEM, low pressure nitrogen adsorption, mercury injection capillary pressure (MICP) and spontaneous fluid [deionized (DI) water and n-decane] imbibition were performed.Most of the visible pores from SEM work in Wufeng and Longmaxi shales are within nm- and μm-size regimes and belong to organic matter (OM) pores. The shapes of OM pore in Longmaxi samples are elliptical, bubble-like, irregular or rounded. Wufeng pores are mainly irregular, linear and faveolated, even though two shales have small depth difference, as well as similar thermal maturity, kerogen type and TOC content. Nano-scale pores in Longmaxi are mainly associated with narrow platelike or slitlike pores with pore size of 3–50 nm; while inkbottle pores are dominant in Wufeng samples and over 88% of the pore volume is contributed by pores with diameter <20 nm. Overall, porosity, pore volume and surface area values from Wufeng samples are much higher than those in Longmaxi, which is mainly correlated with the different TOC contents and mineral compositions. MICP tests show that a total of 5 inflection points (indicative of different connected pore networks) are identified in all pressure regions for Longmaxi, while only 2 for Wufeng in high pressure region with the associated permeability at nano-darcy range. Imbibition curves of n-decane are divided into three stages: the initial stage (Stage Ⅰ), linear imbibition stage (Stage Ⅱ) and late imbibition stage (Stage Ⅲ), and the slopes of linear imbibition stage are around 0.5, suggesting well-connected pore spaces for n-decane. In contrast, imbibition curves for DI water are divided in two stages with linear slopes of between 0.25 and 0.5, indicating moderately-connected pore networks for the movement of DI water. This is consistent with the mixed-wet nature of these shales, with observed weak wettability for hydrophilic, while complete wetting for hydrophobic fluids.     

The use of topology in fracture network characterization

In two-dimensions, a fracture network consist of a system of branches and nodes that can be used to define both geometrical features, such as length and orientation, and the relationship between elements of the network – topology. Branch lengths are preferred to trace lengths as they can be uniquely defined, have less censoring and are more clustered around a mean value. Many important properties of networks are more related to topology than geometry.The proportions of isolated (I), abutting (Y) and crossing (X) nodes provide a basis for describing the topology that can be easily applied, even with limited access to the network as a whole. Node counting also provides an unbiased estimate of frequency and can be used in conjunction with fracture intensity to estimate the characteristic length and dimensionless intensity of the fractures. The nodes can be used to classify branches into three types – those with two I-nodes, one I-node and no I-nodes (or two connected nodes). The average number of connections per branch provides a measure of connectivity that is almost completely independent of the topology. We briefly discuss the extension of topological concepts to 3-dimensions.     

乌泊尔断裂带构造几何学与运动学

乌泊尔断裂带位于帕米尔构造结东北缘,作为揭示青藏高原形成与演化历史的关键地区之一,为碰撞造山作用提供了详细信息,因此厘清乌泊尔断裂带关键构造的形成演化具有重要意义。为研究该断裂带的几何学与运动学特征,本文利用钻测井资料、二维地震反射资料、DEM 高程资料以及喀什地区1∶100 000地质图,以断层相关褶皱理论为指导,对乌泊尔断裂带进行精细构造解析。研究认为,乌泊尔断裂沿走向至少可分为东、西两段,西段构造变形强烈,而东段较弱,构造样式沿断裂走向上有较大差异;垂直于构造走向上可划分出两个等倾角区;乌泊尔地区的变形最早于中新世早期开始,自上新世以来构造变形强烈,乌泊尔断裂在该区域的活动起始于第四纪,具有幕式活动的特点;通过断层相关褶皱分析得到,自中新世至上新世,断裂东段的构造缩短量至少为9.47 km,第四纪以来的构造缩短量至少为11.65 km。第四系生长地层的内部结构受控于基底叠瓦构造和乌泊尔断裂,明确深浅构造的关系能较好得限定研究区关键构造的形成演化过程,可作为复杂构造解析的有效方法。     

结构面对岩体爆破块度分布影响的分形探讨

在前人研究成果的基础上，应用分形几何理论探讨了结构面对岩体爆破块度分布影响的分形规律，得出了几点有益的结论。     

Thin Domain Walls in Lyra Geometry

This paper studies thin domain walls within the frame work of Lyra Geometry. We have considered two models. First one is the thin domain wall with negligible pressures perpendicular and transverse direction to the wall and secondly, we take a particular type of thin domain wall where the pressure in the perpendicular direction is negligible but transverse pressures are existed. It is shown that the thin domain walls have no particle horizon and the gravitational force due to them is attractive.     

西大别造山带中新县-红安地区的变质变形分析

以商麻断裂为界,大别造山带分为东段和西段,西大别造山带是连接桐柏造山带和大别造山带的纽带。通过对几何学和运动学以及变质环境的研究表明：西大别造山带的形态为一个枢纽向西倾伏的巨型背形构造,且有圈层结构,层间存在滑脱面。西大别地区至少存在着3 期构造变形,第一期是南北边界剪切带的形成,第二期是层间滑脱面和榴辉岩透镜体的形成,第三期是晚期的岩体侵入。应力场的统计结果可知,西大别造山带主要受到近南北方向的挤压,统计结果真实地记录了西大别造山带形成时的古应力状态,对应着3 期变形的第一期。有限应变测量结果显示,从北向南岩石的变形强度存在着：强变形带→弱变形带→强变形带→弱变形带→强变形带这种强弱变形带交替出现的规律。通过白云母Ti温度计以及多硅白云母压力计结果显示西大别造山带中新县-红安地区岩石的变质条件为T = 450 ℃～620 ℃,P = 1.0～1.6 GPa,属于高压蓝片岩相到榴辉岩相。     

Estimating basal friction and fluid pressure from the geometry and spacing of frontal faults in Naga fold thrust belt, India

Naga fold thrust belt is an emerging destination for petroleum exploration in eastern India. It is a thin skinned FTB where new initiatives are being taken after a long gap of initial discoveries. In absence of sufficient drilling or quality seismic data in the southern part of the fold thrust belt, fluid pressure regimes remain largely speculative. Using the concept and the formulation for efficient coefficient of basal friction, we have revisited the method and concept of pressure-dependent Coulomb wedge theory for thin skinned thrust belts for deriving the fluid pressure ratio in Naga fold thrust belt. The efficient coefficient of basal friction on the decollement and the fluid ratio of Naga fold thrust belt are estimated to be 0.22 and 0.85 respectively. This indicates an overpressure situation in the wedge. This method of estimating basal friction and fluid pressure is more case-specific and can be obtained from the data of thrust initiation angle and thrust spacing.     

Facies character and depositional architecture of hydrothermal travertine slope aprons (Pleistocene,Acquasanta Terme,Central Italy)

Hydrothermal travertines develop various depositional geometries, from tabular to high-relief mounds or aprons with steep slopes, under the control of local topography, location and geometry of the vents, fault activity, hydrology, water physico-chemical properties, rates of thermal water flow and carbonate precipitation rates. This study focuses on two Pleistocene, tens of metres thick, travertine slope aprons accumulated on fluvial terraces in the Tronto River Valley (Acquasanta Terme, Central Italy) to investigate their facies character, geochemical signature, porosity and evolution of the depositional geometry through time.The two travertine aprons consist of four aggradational-progradational units, vertically and laterally stacked with onlap and downlap stratal terminations, separated by erosional unconformities produced by events of non-deposition and erosion, due to temporary interruptions of vent activity, shifts of the vent location and/or deviation of the flow directions. The travertine units include various depositional environments: 1) smooth slope, 2) terraced slope with metre-scale sub-horizontal pools separated by rounded rims and vertical walls, and 3) sub-horizontal, tens of metres wide ponds. Smooth slope clinoforms are made of centimetre to decimetre thick layers of crystalline dendrite cementstone, laminated boundstone and radial coated grain grainstone, precipitated by fast-flowing water on inclined substrates. Rims and walls of terraced slopes are built by crystalline dendrites and laminated boundstone. Sub-horizontal layers of terrace pools and ponds consist of facies precipitated by slow-flowing to standing water (clotted peloidal micrite dendrite, coated bubble boundstone, raft rudstone) associated with radial coated grains and laminated boundstone. Carbonate coated reeds occur in distal ponds adjacent to toe of slopes or overlie packstone/rudstone with travertine intraclasts and substrate extraclasts, marking events of subaerial exposure and erosion. Travertine facies porosity and permeability range from 4 to 21% and 0.03 to 669 mD, respectively, showing no direct correlation. Stable isotope values (δ¹³C: 5.7–9.3‰; δ¹⁸O −9.6‰ to −12.2‰) are similar to other travertines precipitated by thermal water in Central Italy.This study identifies the centimetre-scale travertine facies variability linking it to the environment of deposition and to the depositional geometry of travertine units affected by the substrate topography and lateral shifts of the active springs. Despite the different scale and facies composition, the geometry of aggradational-progradational units of travertine aprons might resemble marine flat-topped high-relief carbonate platforms. Travertine units in the subsurface, if present with sizes that can be seismically resolved, might be wrongly interpreted as carbonate platforms with steep slopes without a detailed facies analysis.     

准噶尔盆地西北缘红3 井东侧断层构造几何学、运动学模型

红3井东侧断层的成因与中拐凸起的形成与演化密切相关,解析其构造几何学与运动学特征对于揭示中拐凸起自晚古生代以来的构造变形具有积极作用,并对于研究区的油气勘探具有重要意义。本文利用断层相关褶皱理论,不整合面识别及平衡剖面的方法,对红3井东侧断层进行精细的构造解析、建模与构造复原。中拐凸起发育白垩系-侏罗系、侏罗系-三叠系、三叠系-上乌尔禾组、上乌尔禾组底界及佳木河组-石炭系5个区域不整合面。研究认为,红3井东侧断层为一断层传播褶皱模型,发育生长三角,平面上分为北段、中段和南段。受海西晚期及燕山期的区域挤压作用的影响,红3井东侧断层在早二叠世末期（P₁f末期）至中二叠世晚期（P₂w）及早侏罗世晚期（J₁s）至晚侏罗世发生两期传播活动,并在中段发生分支,分支断层的断距较小。早期的断层活动在中段最强,南段其次,北段最弱。中-下二叠统被抬升,遭受大面积剥蚀,地层缩短量约为3.8 km。晚期的断层活动微弱,且只发生在中段和北段,地层缩短量约为200 m。红3井东侧断层自北东向南西方向的传播、推覆作用控制了中拐凸起的主体构造形态,整体具有“南北分段、早晚期构造叠加”的特征。