Fault zone characteristics,fracture systems and permeability implications of Middle Triassic Muschelkalk in Southwest Germany

Fault zone structure and lithology affect permeability of Triassic Muschelkalk limestone-marl-alternations in Southwest Germany, a region characterized by a complex tectonic history. Field studies of eight fault zones provide insights into fracture system parameters (orientation, density, aperture, connectivity, vertical extension) within fault zone units (fault core, damage zone). Results show decreasing fracture lengths with distances to the fault cores in well-developed damage zones. Fracture connectivity at fracture tips is enhanced in proximity to the slip surfaces, particularly caused by shorter fractures. Different mechanical properties of limestone and marl layers obviously affect fracture propagation and thus fracture system connectivity and permeability. Fracture apertures are largest parallel and subparallel to fault zones and prominent regional structures (e.g., Upper Rhine Graben) leading to enhanced fracture-induced permeabilities. Mineralized fractures and mineralizations in fault cores indicate past fluid flow. Permeability is increased by the development of hydraulically active pathways across several beds (non-stratabound fractures) to a higher degree than by the formation of fractures interconnected at fracture tips. We conclude that there is an increase of interconnected fractures and fracture densities in proximity to the fault cores. This is particularly clear in more homogenous rocks. The results help to better understand permeability in Muschelkalk rocks.     

河北省麻子沟铅银矿床地质特征及理想成矿模式探讨

麻子沟铅银矿床为次火岩—中低温热液矿床。次火山岩侵入活动过程中的热液,是成矿的主要热液来源。热液沿断裂破碎带溶解地层中的成矿物,使其在热液中富集,在成矿有利部充填、交代围岩形成矿体或矿化。通过对成矿条件、地质特征、控矿因素、矿化蚀变特征及矿体赋存位置分析,建立理想成矿模式,明确区内的找矿方向。     

The vorticity axis flip and its control on mineralization

This paper discusses the possible role of vorticity axis flip in controlling fluid flow and consequent development of hydrothermal deposits. Structural, kinematic and vorticity data from the vicinity of the Singhbhum Shear Zone (SSZ) are used to propose a two stage model to explain hydrothermal mineralization. It is suggested that in the initial stage, fractures, weak planes, foliations and/or shear zones develop. Fracture permeability is weak at this stage, as a consequence of which fluid pressure builds up. Variation in stress orientation during a later stage of deformation results in enhancement of fracture network, fracture permeability and its anisotropy. If a significant vorticity axis flip accompanies this variation in stress orientation, then it pumps the fluids into the fracture network, thus yielding hydrothermal mineral deposits. In the case of SSZ, the vorticity axis flip is envisaged to have taken place from steeply plunging (anticlockwise) during the early stage, to sub-horizontal during the late stage. The SSZ became a northerly dipping thrust at this late stage and the rotation around the sub-horizontal vorticity axis was such that the rocks comprising the northern block were thrust over southern block (Singhbhum granitoid). According to the author, this vorticity axis flip must have been critical in pumping up the fluids along the SSZ to form quartz veins that host mineral deposits.     

Fracture-zone conditions on a recently active fault: insights from mineralogical and geochemical analyses of the Hirabayashi NIED drill core on the Nojima fault, southwest Japan, which ruptured in the 1995 Kobe earthquake

An 1800-m-deep borehole into the Nojima fault zone was drilled at Nojima-Hirabayashi, Japan, after the 1995 Hyogo-ken Nanbu (Kobe) earthquake. Three possible fracture zones were detected at depths of about 1140, 1300, and 1800 m. To assess these fracture zones in this recently active fault, we analyzed the distributions of fault rocks, minerals, and chemical elements in these zones. The central fault plane in the shallowest fracture zone was identified by foliated blue-gray gouge at a depth of 1140 m. The degree of fracturing was evidently greater in the hanging wall than in the footwall. Minerals detected in this zone were quartz, orthoclase, plagioclase, and biotite, as in the parent rock (granodiorite), and also kaolinite, smectite, laumontite, stilbite, calcite, ankerite, and siderite, which are related to hydrothermal alteration. Biotite was absent in both the hanging wall and footwall across the central fault plane, but it was absent over a greater distance from the central fault plane in the hanging wall than in the footwall. Major element compositions across this zone suggested that hydrothermal alteration minerals such as kaolinite and smectite occurred across the central fault plane for a greater distance in the hanging wall than in the footwall. Similarly, H₂O+ and CO₂ had higher concentrations in the hanging wall than in the footwall. This asymmetrical distribution pattern is probably due to the greater degree of wall–rock fracturing and associated alteration in the hanging wall. We attributed the characteristics of this zone to fault activity and fluid–rock interactions. We analyzed the other fracture zones along this fault in the same way. In the fracture zone at about 1300 m depth, we detected the same kinds of hydrothermal alteration minerals as in the shallower zone, but they were in fewer samples. We detected relatively little H₂O+ and CO₂, and little evidence for movement of the major chemical elements, indicating little past fluid–rock interaction. In the fracture zone at about 1800 m depth, H₂O+ and CO₂ were very enriched throughout the interval, as in the fracture zone at about 1140 m depth. However, smectite was absent and chlorite was present, indicating the occurrence of chloritization, which requires a temperature of more than 200 °C. Only smectite can form under the present conditions in these fracture zones. The chloritization probably occurred in the past when the fracture zone was deeper than it is now. These observations suggest that among the three fracture zones, that at about 1140 m depth was the most activated at the time of the 1995 Hyogo-ken Nanbu (Kobe) earthquake.     

鄂尔多斯盆地延长组次生矿物与裂缝形成时限分析

鄂尔多斯盆地延长组发育大量构造裂缝,对于裂缝的形成机理、成因动力学以及与油气成藏关系都已得到了比较系统的研究,但对于裂缝中充填的次生矿物,以及次生矿物与裂缝形成时限之间的关系,尚鲜有研究。本文在次生矿物的矿化作用和成岩作用分析基础之上,应用碳氧同位素和流体包裹体分析方法,结合区域构造热事件以及盆地热演化史,对次生矿物与裂缝形成时限的约束关系进行研究。首先,通过次生矿物的镜下观察分析,获知充填次生矿物的裂缝为张性裂缝,且可判断裂缝扩展方向;根据成岩作用分析,裂缝在形成时间上早于或同期于次生矿物形成时间。其次,根据延长组储层砂岩和裂缝中碳酸盐胶结物的碳氧同位素分析,得知露头中大量被碳酸盐胶结物充填的E-W 和N-S 向裂缝,在形成时间上早于或与碳酸盐脉体同期形成。最后,结合流体包裹体和盆地埋藏热演化史分析,得知盆内地下大量的热液活动主要发生在140～100 Ma 之间（即早白垩世）,也是盆地大规模成岩作用时期。基于上述分析,充填碳酸盐胶结物的E-W 向和N-S 向裂缝组,在形成时间上,应早于或同期于充填次生矿物的形成时间,即在早白垩世或者早白垩世之前形成。     

Structures and Implications for Fluid Migration in the Jiadi Carlin‐Type Gold Deposit,Guizhou Province,Southwest China

The Jiadi gold deposit is a newly discovered Carlin‐type gold deposit in the Guizhou Province, Southwest China. This deposit is structurally controlled by a shallow fold–fault superimposed system along the Lianhuashan trend. Field geological investigations, structural analysis, and mathematical research are conducted to study its structures and hydrothermal fluid flow process. Geological investigations (i.e. sections, stope, and drill hole) indicate that the structures are dominated by NE‐trending folds, NWW‐trending folds, and faults. A trend‐surface analysis of the low interformational fracture zone suggests that the overall distribution of the Lianhuashan trend is controlled by the NE‐trending Lianhuashan anticline. Nearly all primary Carlin‐type gold deposits are distributed along the southeastern flank where the fold axis changes from NE to EW. Gold orebodies are hosted by the interformational fracture zones and primarily situated at the transitions from the high‐value areas to the low‐value areas of the interformational fracture zones. A stress analysis on the hydrothermal veins indicates that they are of tenso‐shear properties. The ore‐forming elements (Au, As, Sb, Hg, and Tl) of the hydrothermal veins from the interformational fracture zones and intrusive breccia body present strong positive anomalies compared with those from the adjacent wall rocks. According to the development patterns of the ore‐forming elements and hydrothermal veins, a migration process of the ore‐forming fluids is proposed: the deeply sourced ore‐forming fluids migrated vertically to shallow crust along an intrusive breccia body, subsequently flowed horizontally along the interformational fracture zones accompanied by gold precipitation in the early stage, and finally migrated outward along steep micro‐fractures during following stages.     

甘肃银硐梁锑矿床地质特征及控矿因素分析

近些年来,在西秦岭锑成矿带中发现了中型规模的甘肃银硐梁锑矿床。通过论述该锑矿床的地质特征,分析并讨论该矿床的控矿因素及找矿标志。结果表明: 该锑矿床主要赋存于三叠纪官亭群中部建造层第二岩性段、钙质硅化石英砂岩夹泥质粉砂岩的断层破碎带和层间破碎带中; 锑矿化明显受地层和断裂破碎带控制,为成矿提供成矿物质、热液条件和赋存空间,较早形成的NW向断裂是导矿构造,较晚形成的NE向次级断裂是赋矿构造; 成矿物质主要来源于地层,成矿热动力主要来源于构造运动,成矿作用以热液充填为主; 银硐梁锑矿床属于低温热液裂隙充填型层控矿床。     

Deep crustal growth of quartz, kyanite and garnet into large-aperture, fluid-filled fractures, north-eastern Connecticut, USA

Abstract A petrographic and petrological analysis of exceptionally well-preserved hydrothermal veins from the Merrimack synclinorium, north-eastern Connecticut, has been carried out in order to place new field-based constraints on fracture aperture dimensions and porosity in the lower continental crust. The veins preserve substantial open space today in outcrop, and contain mineral assemblages including subhedral to euhedral crystals of quartz, kyanite and almandine-rich garnet. Textural evidence indicates unequivocally that the vein minerals grew into macroscopic (mm- to cm-scale) open space between the vein walls. The veins are interpreted to have been large-aperture fractures along which significant advective fluid infiltration and chemical reaction occurred. The porosity of the rock mass due to open space between fracture walls today is c . 0.3%, but it could have been as large as several percent when the flow system was active. Quantitative thermobarometry results from vein mineral assemblages indicate that the fractures formed at pressures and corresponding crustal depths of c. 0.8 GPa and c. 30km, and temperatures of 550–600° C. The depth of fracture formation corresponds to published estimates of the maximum burial depth of the Merrimack synclinorium during the Acadian orogeny. The formation of large-aperture fractures could increase significantly the transient permeability of the deep crust, and therefore influence metamorphic heat and mass transfer.     

渤海海域石臼坨—辽西凸起覆盖型潜山储集层发育特征与分布模式*

渤海海域发育勘探潜力巨大的覆盖型潜山,这类潜山储集层的发育特征及分布模式是当前潜山油气勘探研究的重点和难点。利用地震、测井、铸体薄片、井壁岩心、常规物性、扫描电镜和X衍射等资料,开展了石臼坨—辽西凸起覆盖型潜山储集层的发育特征、主控因素和分布模式研究。研究结果表明: (1)覆盖型潜山以长英质含量较高的混合花岗岩为主,发育多种类型的溶蚀孔隙和裂缝,其中构造裂缝是最主要的储集空间。储集层平均孔隙度为2.2%,平均渗透率为0.445×10^-3 μm²。覆盖型潜山自上而下可划分为风化黏土带、风化砂砾岩带、风化裂缝带、裂缝发育带、相对致密带和基岩带。 (2)富长英质的岩石为裂缝型储集层的形成提供了物质基础,较高的长英质含量利于构造成缝和风化、淋滤、溶蚀改造。 (3)印支期—燕山期的强烈隆升是形成优质风化壳储集层的必要条件,而多期次构造作用叠加是潜山规模裂缝型储集层形成的关键,储集层距印支—燕山主控断裂的远近和所处构造部位进一步影响了裂缝的发育。 (4)风化淋滤对于覆盖型潜山储集层的改造具有重要作用,是控制储集层垂向分带性的主要因素。 (5)建立了覆盖型潜山储集层的分布模式,叠合破碎带的风化裂缝带和裂缝发育带是优质储集层的有利发育部位,二层结构潜山风化壳更为发育,多期构造活动叠加区域潜山内幕裂缝带厚度更大,裂缝发育带和破碎带发育更为密集。     

Characterization of the hydrothermal systems associated with Archean VMS-mineralization at Panorama,Western Australia,using hyperspectral,geochemical and geothermometric data

Airborne hyperspectral imagery was used to study the distribution of white mica minerals in Archean (3.2 Ga) submarine hydrothermal systems associated with volcanogenic massive sulfide mineralization in a well-exposed volcanic sequence of the Soansville greenstone belt in the Pilbara, Western Australia. White mica mineral abundance and distribution maps were compared with published hydrothermal alteration maps and differences were interpreted using whole-rock geochemistry and temperature estimates from oxygen isotope geothermometric studies of hydrothermally altered rocks. Three different zones were identified from the hyperspectral imagery: 1) Al-rich white mica zones in the upper parts of the volcanic sequence which are related to recharge of unevolved seawater, 2) Al-poor white mica zones at middle and upper levels of the volcanic sequence predominantly related to K alteration by more-evolved hydrothermal fluids, and 3) high to intermediate Al-content white mica zones in lower levels of the sequence and in cross-cutting zones related to intense alteration by laterally flowing and upwelling evolved fluids. The integrated study of the spatial distribution of hyperspectrally detected white mica minerals together with published maps and rock analyses allowed characterization of the hydrothermal systems and reconstruction of paleo fluid pathways.     

Hydromechanical properties and alteration of natural fracture surfaces in the Soultz granite (Bas-Rhin, France)

Natural fractures are characterized by rough surfaces and complex fluid flows. A large distribution of apertures (residual voids) within their walls and the presence of contact points (in situ normal loads) produce heterogeneous flows (channeling). The resulting permeabilities, porosities or fluid–rock exchange surfaces cannot be realistically modeled by parallel and smooth plate models. Four natural fractures are sampled at different depths and degrees of alteration in the Soultz sandstone and granite (EPS1 drillhole, Soultz-sous-Forêts, Bas-Rhin, France). The fracture surfaces are measured with mechanical profilometry and maps of asperity heights (XYZ). Resulting local apertures (XYe) are then calculated. A statistical study of the surface profiles (XZ) show that the fractures are more or less rough and tortuous according to the types of alteration. Altered samples are characterized by smoother surfaces of fractures. Such differences imply that (i) the average fracture aperture is not representative for the whole fracture and that (ii) the different local apertures should be integrated in hydraulic and mechanical models. A hydraulic model (finite difference calculations) of fluid flow, taking into account the elastic closure (Hertz contact theory) of fractures with depth, is used. Maps of contact points and relative local loads within the fracture planes are compared to flow maps. They show different channeling of fluid flows. Strongly altered fractures are characterized by homogeneous fluxes despite the presence of numerous contact zones during the closure of fracture. By contrast, fresh fractures develop, increasing fluid flow channels with depth.Fracture closure (increasing normal stress) does not systematically increase the channeling of fluid flow. There is evidence for a general smoothing out of the irregularities of the fracture walls due to precipitation of secondary minerals, indicating that the cubic law can be commonly valid, also at great crustal depth but this validity depends on the degree of fracture alteration. Mineralogical and geochemical observations, thus, should be taken into account to perform more accurate permeability calculations and models of fluid circulation in fracture networks.     

西昌盆地东吴期深部热液作用及其对志留系碳酸盐岩储层的改造

晚古生代中国西南地区发生了"峨眉地裂运动",与此相关的深部热液作用在西昌盆地非常发育发育.对QB1井的研究表明,志留系第Ⅲ期裂缝及其中充填的异形白云石和石英是东吴期热液作用的产物,异形白云石的δ~(13)C值、δ~(18)O值异常偏负、锶同位素值异常偏高、异形白云石和石英内原生包裹体气相部分富含氮气(N_2)是这一期热液作用的地球化学标志;深部热液为幔源岩浆热液与盆地基底深变质岩地层热液的混合液,它们沿垂向断裂通道和侧向裂缝系统运移进入志留系,导致了不规则的张性热液破裂裂缝的形成、裂缝内异形白云石和石英的部分沉淀、以及溶蚀作用的发生;它们产生的缝洞系统,对西昌盆地志留系裂缝性储层的形成有重要贡献.     

川西丹巴地区磨子沟金矿床金、银赋存状态及成因

磨子沟金矿床位于四川省丹巴县,大地构造位置位于扬子准地台西缘,松潘-甘孜造山带东缘,泥盆系危关组炭质千枚岩、板岩是主要的赋矿围岩。成矿过程分为沉积成矿期、热液成矿期和表生风化期,其中热液期是金的主要成矿期。通过显微镜观察,扫描电镜、电子探针成分分析,矿物晶体化学式计算等手段和方法,研究了矿床中Au、Ag的赋存状态和主要载金矿物的特征。金以裂隙金、包裹体金、粒间金为主,银主要以类质同像赋存于方铅矿和硫盐矿物中。载金矿物黄铁矿生物结构发育,表明生物成矿作用是金矿床形成过程中的重要作用。矿体受特定层位和断裂的控制,围岩蚀变强烈。根据矿床产出的大地构造环境、赋矿围岩特征、构造控矿、层位控矿、矿物共生特点等分析结果,丹巴磨子沟金矿床为沉积-热液改造型金矿床。     

湘西沃溪钨锑金矿床地质地球化学特征

沃溪钨锑金矿床产于元古界板溪群马底驿组中、上段紫红色绢云母板岩中,受层间断裂带控制。矿体具斜列延伸、多层产出、近似等间距分布特点,见有层间石英脉、网状石英脉和节理裂隙脉三类矿体。金矿物以次显微、显微金为生,主要赋存于以黄铁矿、辉锑矿为主的硫化物中,As、Sb是其标型元素。成矿物质与赋矿地层密切相关,成矿流体是非岩浆源的,成矿作用是在中低温度、偏低盐度、中性略偏酸性的变质热液中发生的,构造运动对成矿过程起着控制作用。矿床属于火山沉积—变质热液成因。     

Fault/fracture density and mineralization: a contouring method for targeting in gold exploration

A widely observed correlation between high fracture density and mineralization throughout terranes and geological time indicates a fundamental underlying ore-forming process. In Archaean greenstone-hosted deposits, high-density fracturing was accompanied by enhanced fluid flow during fault/fracture network development, producing regional-scale fluid pressure gradients that focussed hydrothermal fluids into preferentially fractured areas. Fracture density is both increased and decreased during faulting and fault healing, and fracture density accumulates over time, in zones of high palaeo-fluid flow. Localised zones where the density of fracturing is increased by deformation, become permeability nodes for migrating hydrothermal fluids leading to large zones of alteration and gold precipitation. The Ora Banda mining centre in Western Australia contains significant gold deposits that appear to demonstrate a close association between high-density fracturing and gold precipitation. Fracture density in the Ora Banda mines was enhanced by fault–fault intersections, fault–contact intersections and changes in fault geometry. The mine-scale relationships between fracture density and gold mineralization are repeated at smaller and larger scales, hence these relationships may be used in targeting for gold exploration. Contouring the density of fracturing in a region provides a semi-quantitative way to rank areas for exploration and uses data from mapping, drilling and high-quality geophysical data as a basis for analyses. Fracture density contouring is complementary to other prospectivity-analysis methods.     

Hydrothermal fluids responsible for the formation of precious minerals in the Nigerian Younger Granite Province

Preliminary investigations in the Younger Granite Province of Nigeria have revealed that precious and semi-precious minerals like rubies, sapphires, emeralds, aquamarine, zircon and fluorite can be found in the region. The gem minerals are shown to have been produced either by direct deposition along fissures, veins and greisens by hydrothermal fluids or as a result of hydrothermal fluids reacting with wall-rocks. These wall rocks are either biotite granites from which the hydrothermal fluids originated or basement rocks or any other rocks which the biotite granites intrude and their residual hydrothermal fluids have invaded. The hydrothermal fluids appear to have been rich in alkalis (Na⁺, K⁺, etc.), rare elements (Be, Zr, F, REE, etc.) and siliceous. As these fluids rose through fractures and channel ways through the rocks, they either deposited the gem minerals in the fractures at the appropriate stability conditions or reacted with the wall-rocks producing the gem minerals at the expense of elements like Ca and A1 in the minerals of these rocks.     

阿尔金大平沟金矿床地质特征及成因初探

大平沟金矿处于阿尔金山北坡太古界托格拉格布拉克岩群的NWW向强应变构造带中，矿体主要为石英脉型和含金蚀变岩型，其形态，产状，规模严格受韧脆性剪切带控制，含矿围岩主要为韧脆性变形的闪长质碎粒岩，糜梭岩，与金矿化有关的围岩变主要有黄铁矿化，硅化，钾化等，且随蚀变强度的增强，金含量增高，属中低温变质，岩浆热液复合因型金矿床。     

Characteristics of hydrothermal-structure-controlled fracture-vug dolomite reservoir and its influence on oil-water distribution: Lower Cretaceous,Baiyinchagan sag,Erlian Basin,North China

Fractures and vugs were used as the primary dolomite reservoir space in the study area, which improved the reservoir’s physical properties and influenced the distribution pattern of oil and water that were developed in the Upper Tenger Formation, Lower Cretaceous, Baiyinchagan sag, Erlian Basin. Based on the core observation data, thin slice analysis, and image logging, the cave-fractured reservoir was primarily developed in the actic region near the side of a depositional fault. Tectonic and diagenetic fractures were the primary types of fractures. High-angle tectonic fractures in the closure and open status were developed well in dolomitic mudstone, while a low-angle fracture and reticulate fractures were developed in the tectonic-hydrothermal hybrid process and were filled with hydrothermal minerals. The reservoir was located in low-lying land; therefore, detrital grain pressolution fractures were formed by burial diagenesis. Intergranular and intrangranular dissolved pores, which were formed by hydrothermal activity, were developed primarily in the highly dolomite lithology. According to the diagenesis temperature of dolomite from a carbon-oxygen isotope analysis, multiple hydrothermal fluid injection events occurred, and dolomitization ensued before massive hydrocarbon migration. The dissolution of organic acids formed by hydrocarbon charges after dolomitization and inorganic acid produced by burial di agenesis for soluble minerals effectively promoted the reservoir properties. Strong heterogeneity due to lithology and fracture-vug systems led to intricate oil-water relationships. Four statuses occurred, including cave-fracture oil, isolated oil, stored oil, isolated water, and stored water. The oil-water distribution patterns were established based on the core observation.     

Petrophysical characterization and natural fracturing in an olivine-dolerite aquifer

As part of a study investigating the naturally-occurring fractures in mafic rocks, two holes were drilled 450 m apart through the Palisades dolerite sill in New York. Well-2 is 229 m deep and Well-3 was drilled to 305 m, both penetrating through the sill and into the underlying Triassic sediments of the Newark Basin. Both holes were logged with downhole geophysical tools, including the BHTV, which acoustically images fractures intersecting the well. Understanding the fracture pattern, density, and porosity in the sill is essential for identifying possible zones of active fluid flow and high permeability. Using the BHTV logs, 96 and 203 fractures were digitally mapped within the sill in Well-2 and Well-3, respectively. Most fractures appear to dip steeply (76-78°). There is a shift in fracture orientation, however, and these fractures may or may not be continuous over the short lateral distance between Well-2 and Well-3. The lithology of the sill as identified by drill chips is nevertheless continuous between the holes. Both intersect a 7 m thick olivine-rich layer about 15 m above the bottom of the sill. Several fractures identified in Well-2 have large apparent aperture (>6cm) which correspond to high porosity zones (6-14%) observed in the logs. Resistivity logs were used to compute porosity using Archie's law and match well with the neutron porosity log in Well-2. We use the relationship between porosity and fracture aperture within the sill at Well-2 to infer the porosity in Well-3. High-porosity, large-aperture zones, including the target olivine layer, are identified in both holes. Changes in the temperature gradient log indicate active fluid flow in the sill, although flow appears to be most active in the sediments. Direct field measurements of bulk permeability, hydrologic modeling of fluid flow and calibration of fracture and log porosity will be undertaken in the future.     

济阳坳陷沾化凹陷罗家地区古近系沙河街组页岩储集特征分析*

利用岩石薄片和扫描电镜分析等测试技术, 可以将济阳坳陷罗家地区古近系沙河街组页岩段储集空间分为孔隙和裂缝两大类。孔隙又可以分为黏土矿物晶间孔、碳酸盐矿物晶间孔、黄铁矿晶间微孔、碎屑颗粒溶孔和砂质粒间微孔5个亚类;裂缝分为成岩裂缝和构造裂缝两大类, 成岩裂缝又可以分为层间裂缝和粒缘裂缝两类。裂缝与基质孔隙之间, 存在一个微米尺度的重合带, 反映了储集空间发育继承性的特点, 油气聚集在以层间裂缝为中心, 粒缘裂缝等次级裂缝和较大的碳酸盐晶间孔为骨架, 以各类晶间孔隙、黏土微孔和溶蚀孔隙为基质的储集空间网络中。储集空间发育与岩性关系密切, 纹层状泥质灰岩物性较好, 相应的页岩物性具有基质渗透率极低和裂缝导流能力较强的特点。