湖泊三角洲平原砂体的露头构形分析

本文应用等级界面与构形单元分析的方法，详细研究了鄂尔多斯盆地东北缘神木县考考乌素沟地区侏罗系延安组湖泊三角洲平原砂体的几何形态、空间配置和内部构形，并重点剖析了三角洲平原上的分流河道（含天然堤）和决口扇砂体，识别出５级界面体系，划分出１７种储层岩性相和４种构形单元。各级界面分别代表不同规模的非均质性，界面性质及伴生的渗透性隔挡层（泥质夹层）的分布控制了砂体的垂向和侧向连通性。储层岩性相是一种物质－能量单元，它们在砂体内的分布有一定规律。构形单元则是一种三维岩石单元，由第３至５级界面限定，具有各自特征的储层岩性相组合。界面和储层岩性相都是沉积水动力条件的综合反映，它们的不同组合反映了砂体内部非均质性的细微变化，并控制砂体的物性特征。物性在砂体内的分布按构形单元自然分区，高孔渗带主要分布在３至５级界面之上，多个构形单元和界面在垂向或侧向。的叠置，导致物性出现多阶正韵律的变化。代表水动力条件较强的储层岩性相，其物性较好，反之则差。     

地层切片技术在复杂勘探区储层预测与地质体识别中的应用

研究并讨论地层切片技术在复杂断陷盆地岩相识别中的应用及对策,以准确反映盆地中沉积体系的展布,精细刻画振幅型和结构异常型沉积体系.应用地层切片技术,结合三维精细解释结果及三维可视化方法,在海拉尔盆地贝西次凹霍1井区识别了下白垩统大磨拐河组河道的展布并刻画了下白垩统南屯组扇体发育的特征.     

Facies architecture of a submarine fan channel–levee complex: the Juniper Ridge Conglomerate, Coalinga, California

The Upper Cretaceous Juniper Ridge Conglomerate (JRC) near Coalinga, California, provides a rare, high-quality exposure of a submarine channel to overbank transition. The facies architecture of the JRC comprises a thick, predominantly mudstone sequence overlain by a channellized conglomerate package. Conglomeratic bounding surfaces truncate successions of interbedded turbiditic sandstones and mudstones both vertically and laterally. Thick-bedded, massive sandstones are interbedded with conglomerates. Facies architecture, palaeocurrent indicators, slump features, sandstone percentages and sandstone bed thickness trends lead to the interpretation that these elements comprise channel and overbank facies. A vertical sequence with conglomerate at the base, followed by thick-bedded sandstone, and capped by interbedded turbiditic sandstone and mudstone form a fining-upward lithofacies association that is interpreted as a single channel-fill/overbank system. Three similar lithofacies associations can be related to autocyclic processes of thalweg migration and submarine fan aggradation or to allocyclically driven changes in sediment calibre.     

嫩江现代河流沉积体岩相及内部构形要素分析

嫩江是松辽盆地北部一条多河型河流。本文以黑龙江省富裕县塔哈乡大马岗嫩江现代河流沉积露头为例,运用Miall结构要素分析法对嫩江现代河流沉积体岩相类型、层次界面及内部构形要素进行了系统研究,表明大马岗沉积体主要由块状层理细砾相、大型及小型低角度槽状交错层理细砂相、同沉积变形层理细砂相、波状交错层理细砂相、薄层状粉砂质泥与细砂互层相、微波状层理粉砂相、块状层理泥质粉砂相、水平层理泥相、块状层理粉砂质泥相等16种岩相构成,不同岩相空间分布变化差异较大。在大马岗沉积体内部识别出1～5级层次界面,划分出具有成因意义的7种构形要素:河道、砾质坝、侧向加积沉积体、单一侧积砂层、纹层砂席、砂底形及越岸细粒沉积,这种构形要素的划分丰富了Miall的分类方案。     

The effect of depositional environment on coal distribution and quality parameters in a portion of the highveld coalfield,South Africa

Eight successive lithofacies associations are identified and described; they are each laterally continuous and represent a certain depositional phase throughout the study area. These are related to sedimentary processes, from which a three-dimensional paleoenvironmental model is derived. Subsequently, coal distribution and coal quality characteristics are linked to the depositional features of the model.The identified depositional phasescommenced with subglacial, glaciofluvial and glaciolacustrine settings, with associated Gilbert-type deltas. These are followed by meandering and minor braided fluvial settings, characterized by laterally and vertically highly variable lithofacies, in which the main coal-bearing strata were formed.Coal distribution and quality parameters (ash and volatile matter content, calorific value) are closely related to paleoenvironmental characteristics. Major changes of coal distribution and quality parameters are mainly associated with active and abandoned channels and these parameters are less variable in floodplain settings.     

成都平原东郊台地中更新统合江组沉积特征及工程地质意义

通过地层沉积序列、粒度特征、砾石特征综合分析认为,成都平原东郊台地中更新统合江组为河流相沉积,垂向上具有明显的"河流二元"结构特征,主要以细粒沉积物为主,底部砾石层多为中-粗砾,磨圆较好,具有定向性。该组可细分为河道、边滩、堤岸-河漫3种沉积微相类型,对应发育3种岩相类型。河道砾石岩相沿十陵镇-红河镇-大面镇一带呈北西-南东向展布,边滩砂坝岩相集中发育于大面镇-西河镇东侧古河道凹岸处,堤岸-漫滩粘土岩相广泛分布于研究区内。这3种岩相特性及分布对工程建设的影响存在差异:河道砾石层作为地下水储集层的同时,水溶蚀使其地层结构稳定性被破坏,影响工程稳固技术的选择;边滩砂坝分布较为集中,对区内工程建设影响面最小;堤岸-河漫粘土广泛分布,是一种分布稳定的软弱层,对地下水有一定的封闭效果,同时软弱层的特性使其降低了边坡、坝体的稳定性。     

Architectural Model of a Dryland Gravel Braided River, based on 3D UAV Oblique Photogrammetric Data: A Case Study of West Dalongkou River in Eastern Xinjiang, China

Three-dimensional unmanned aerial vehicle(UAV) oblique photogrammetric data were used to infer mountainous gravel braided river lithofacies, lithofacies associations and architectural elements. Hierarchical architecture and lithofacies associations with detailed lithofacies characterizations were comprehensively described to document the architectural model, architectural element scale and gravel particle scale.(1) Nine lithofacies(i.e., Gmm, Gcm, Gcc, Gci, Gcl, Ss, Sm, Fsm and Fl) were identifi...     

东营凹陷沙三中亚段三角洲前缘滑塌型重力流岩相类型及其分布特征

以东营凹陷沙三中亚段三角洲前缘滑塌型重力流砂体为研究对象,利用三维地震、钻井岩心、测录井和分析测试等资料,开展三角洲前缘滑塌型重力流砂体岩相和岩相组合类型划分及分布特征研究。根据泥质含量和沉积构造,划分出13种岩相类型,其中块状层理砂岩相在研究区最为发育。以泥岩、冲刷面或岩相转化面为界,划分出20种岩相组合类型,分为5大类,分别是保留原始沉积构造的岩相组合、变形构造发育的岩相组合、块状层理和碎屑发育的岩相组合、下部碎屑流和上部浊流沉积的岩相组合,以及不完整鲍马序列的岩相组合,反映重力驱动事件中的滑动、滑塌、碎屑流、碎屑流-浊流、浊流沉积作用。根据不同类型重力流的垂向组合和典型剖面岩相分布特征,认为从盆地斜坡到盆地平原,重力流呈现滑动-滑塌-碎屑流-浊流演化特征,滑塌近端主要发育滑动作用岩相组合和滑塌作用岩相组合,滑塌中部主要发育碎屑流岩相组合和碎屑流与浊流过渡转化岩相组合,滑塌远端主要发育浊流作用岩相组合。     

藏北安多-巴青地区侏罗纪含礁层系岩相及沉积环境

根据岩性及其组合特征,本文将西藏北部安多—巴青地区侏罗纪含礁地层划分为流水成因的颗粒岩岩相、流水成因的碎屑岩岩相、复成因的泥晶—泥质灰岩岩相、生物及生物化学成因的障积岩岩相、生物及生物化学成因的粘结—障积岩岩相和生物及生物化学成因的骨架岩岩相等6大类型,计16种岩相。它们构成了潮坪相组合、台地浅滩相组合、开阔台地相组合和台地生物礁相组合共4种岩相组合,并由下而上有规律地形成2种岩相序列,即陆源碎屑与碳酸盐混合台地相序列和碳酸盐台地相序列。     

辫状河砂体储层沉积学研究──以张家口地区露头砂体为例

本文从储层沉积学的角度,对张家口地区辫状河砂体的成因进行了分析,划分了3级层次界面和6种岩石相类型,对沉积作用和成岩作用与储层物性的关系进行了探讨。指出沉积作用是影响砂体物性的主要因素,成岩作用对物性的改造受沉积作用控制。粒度中值和泥质含量与储层物性密切相关,胶结物对孔隙度的影响大于对渗透率的影响。研究表明,砂岩相与储层物性能建立起很好的对应关系,代表高能环境的砂岩相总是对应相对较好的储层物性;界面对储层的影响表现在:1级界面控制了砂体的几何形态和规模,2级界面控制了单砂体的宏观非均质性,3级界面控制了高孔、渗区的分布。最后建立了辫状河砂体的一维和二维储层地质模型,这将对油田的开发设计起指导作用。     

Stratal composition and stratigraphic organization of stratal elements in an ancient deep‐marine basin‐floor succession,Neoproterozoic Windermere Supergroup,British Columbia,Canada

Despite a globally growing seismic and outcrop analogue data set, the detailed (centimetre to decametre) internal stratal make up of deep‐marine basin‐floor ‘channelized‐lobe’ strata remain poorly known. An ancient analogue for modern, mixed‐sediment, passive margin, deep‐marine basin‐floor fans is the well‐preserved Neoproterozoic Upper and Middle Kaza groups in the southern Canadian Cordillera. This succession is a few kilometres thick and comprises six sedimentary facies representing deposition from different kinds of sediment‐gravity flows. Representative lateral and vertical assemblages of one or more of these facies comprise six stratal elements, including: isolated scours, avulsion splays, feeder channels, distributary channels, terminal splays, and distal and off‐axis fine‐grained turbidite units. The internal characteristics of the various stratal elements do not differ from more distal to more proximal settings, but the relative abundance of the various stratal elements does. The difference in relative abundance of stratal elements in the kilometre‐scale stratigraphy of the Kaza Group results in a systematic upward change in architecture. The systematic arrangement of the stratal elements within the interpreted larger bodies, or lobes, and then lobes within the basin‐floor fan, suggests a hierarchical organization. In this article a hierarchy is proposed that is based on avulsion but, also importantly, the location of avulsion. The proposed avulsion‐based hierarchical scheme will be a useful tool to bridge the scalar gap between outcrop and seismic studies by providing a single stratigraphic framework and terminology for basin‐floor stratal elements.     

Progressive changes in sedimentary facies and stratal patterns along the strike-slip margin,northeastern Jinan Basin (Cretaceous), southwest Korea: implications for differential subsidence

In strike-slip basins, proximal stratal patterns are a function of displacement on basin-bounding faults. In order to better understand factors that control changes in sedimentary facies and stratal patterns of the northeastern part of the Jinan Basin (Cretaceous), a strike-slip basin, we made a detailed analysis of sedimentary facies, depositional architecture and paleoflows. The sedimentary successions can be grouped into five facies associations representing five depositional environments: (1) facies association FA I (alluvial fan); (2) FA II (small-scale Gilbert-type delta); (3) FA III (large-scale, steep delta slope); (4) FA IV (base of large-scale, steep delta slope and prodelta); and (5) FA V (lacustrine plain). The successions are divided into two distinct sedimentary fills on the basis of facies associations, depositional architecture and paleocurrents: (1) marginal fill and (2) longitudinal fill. The marginal fill (ca. 3.2 km thick) is present along the strike-slip basin-bounding fault. The lower part of the marginal fill (ca. 1.3 km thick) consists of alluvial-fan deposits (FA I) along the bounding fault which are transitional northward to small-scale Gilbert-type delta (FA II) and lacustrine plain (FA V) deposits. The upper part of the marginal fill (ca. 1.9 km thick) contains large-scale, steep delta slope (FA III) and base of delta slope/prodelta (FA IV) deposits accompanied with a northward change in facies associations. In the marginal fill, the successive alluvial fan, small-scale Gilbert-type delta and large-scale, steep delta/prodelta deposits are overlapped (shingled) northeastward. The longitudinal fill (ca. 2 km thick) is characterized by eastward overlapped stacks of large-scale, steep delta slope (FA III) and base of delta slope/prodelta (FA IV) deposits with a westward progradation. The longitudinal fill was overstepped by the marginal fill. The northeastward shingled geometry of the marginal fill was most likely caused by sinistral strike-slip displacements on the basin-bounding fault. The slightly oblique (northward) progradation of the marginal fill was due to the northward basin-floor tilting. In the marginal fill, the progressive changes in facies and depositional architecture from the lower alluvial fan/small-scale Gilbert-type delta to the upper large-scale, steep delta/prodelta are suggestive of increase in basin subsidence along the strike-slip basin margin that was closely related to the variation in displacement on the basin-bounding fault. The sinistral strike-slip movements on the bounding fault also caused the eastward overlapping of the longitudinal fill.     

鄂尔多斯盆地西缘奥陶系拉什仲组复合水道沉积特征及演化

鄂尔多斯盆地西缘奥陶系拉什仲组发育一套砂泥互层的深水重力流沉积,其下部重力流复合水道发育。综合野外实测、薄片和粒度分析等,探讨复合水道沉积特征、形成过程及主控因素,最终建立其沉积模式。结果表明：(1)研究区发育5种岩相和3种岩相组合,即块状层理砾屑灰岩相(Cm)、粒序层理细—粉砂岩相(Sg)、平行层理砂岩相(Sp)、交错层理粉砂岩相(Sc)、水平层理(泥)页岩相(Sh),分别代表碎屑流沉积(Cm)、浊流沉积(Sg, Sp, Sc)及深水原地沉积(Sh);(2)根据复合水道内部单一水道形态、岩相组合及粒度等将复合水道分为4个期次,反映重力流能量由强到弱的变化过程;(3)复合水道多期次发育与相对海平面升降、沉积物供给、构造运动和重力流规模及能量变化密切相关;(4)重力流沉积为斜坡—盆地环境中复合水道沉积模式。该研究可补充对研究区重力流水道认识,为油气勘探提供借鉴。     

Sedimentology and facies analysis of Miocene mixed siliciclastic–carbonate deposits of the Dam Formation in Al Lidam area,eastern Saudi Arabia

The Burdigalian mixed siliciclastic–carbonate deposits of the Dam Formation are well-exposed in Al Lidam area, in the eastern province of Saudi Arabia. They represent a shallow part of the Arabian plate continental margin. The Dam Formation is correlatable to the Miocene reservoirs in both Iran and Iraq. Therefore, studying the Dam Formation lithologic heterogeneity in a small distance with high resolution could help in further work related to pattern prediction of the Miocene reservoir properties. High-resolution sedimentological investigation was carried out through six outcrops. The facies parameters (lithology, sedimentary structures, main fossils, paleocurrent patterns and geometries of the sedimentary bodies) were described. The results revealed 15 lithofacies that have been further grouped into 7 lithofacies associations 5 of which are carbonates and include (1) interbedded dolostone and evaporates, (2) microbialite buildup, (3) ooid-dominated grainstones, (4) burrowed skeletal peloidal wackestone–packstone and (5) mollusc-dominated wackestone–packstone. The remaining two associations are of siliciclastics and include (6) intertidal siliciclastics and (7) wave-dominated siliciclastics. These lithofacies were interpreted to reflect deposition in a mixed siliciclastic–carbonate ramp system that includes subtidal, shoreface, intertidal, foreshore, supratidal and estuarine deposits in a shallowing-upward succession. Each one of these lithofacies association has distinct geometry and architecture pattern. Oolites and heterozoan lithofacies occur as sheets and show great continuity along the strike direction. Oolites pass laterally in the dip direction into more skeletal- and peloid-dominated zones, whereas heterozoan lithofacies stay continuous in the dip directions and change from siliciclastic to carbonate heterozones. In contrast, microbialite lithofacies lack continuous beds and occur as localised bioherms and biostroms. Channelised lithofacies are restricted laterally into isolated channel bodies and vertically in the contact boundary between siliciclastic and carbonate lithofacies, whereas the interbedded dolostone and evaporite lithofacies form distinct, relatively thick continuous layers. With continuous exposures in both strike (1.2 km) and dip (0.15 km) directions, the outcrops in the Al Lidam area provide unique opportunity to study the heterogeneity among lithofacies of the mixed siliciclastic–carbonate system of the Dam Formation. Such study may provide insights to predict occurrence and distribution of lithofacies bodies in their equivalent reservoirs which are important for reservoir characterisation.     

Lithofacies Clustering Using Principal Component Analysis and Neural Network: Applications to Wireline Logs

Both statistical methods and artificial neural network (ANN) have been used for lithology or facies clustering. ANN, in particular, has increasingly gained popularity for clustering of categorical variables as well as for predictions of continuous variables. In this article, we discuss several counter examples that show deficiencies of these techniques when used for automatic lithofacies clustering. Our examples show that the lithofacies clustered by ANN alone or ANN in combination with principal component analysis (PCA), as commonly used, are highly inconsistent with the benchmark charts based on laboratory results. We propose several techniques to overcome these problems and improve the clustering of lithofacies, including (1) classification of lithofacies using the minor or intermediate principal component(s), (2) rotation of a principal component before using ANN for clustering, (3) cascading two or more PCAs and ANNs for clustering lithofacies or electrofacies, and (4) classifying lithofacies with demarcated stratigraphic reference classes.     

Depositional facies and stratal geometry of an Upper Carboniferous prograding and aggrading high-relief carbonate platform (Cantabrian Mountains, N Spain)

Seismic‐scale continuous exposures of an Upper Carboniferous (Bashkirian–Moscovian) carbonate platform (N Spain) provide detailed information about the lithofacies and stratal geometries (quantified with differential global positioning system measurements) of microbial boundstone‐dominated, steep prograding and aggrading platform margins. Progradational and aggradational platform‐to‐slope transects are characterized by distinct lithological features and stratal patterns that can be applied to the understanding of geometrically comparable, high‐relief depositional systems. The Bashkirian is characterized by rapid progradation at rates of 415–970 m My^?1. Characteristic outer‐platform facies are high‐energy grainstones with coated intraclasts, ooids and pisoids, moderate‐energy algal‐skeletal grainstones to packstones and lower energy algal packstone and boundstone units. The Moscovian aggradational phase is characterized by aggradation rates of 108 m My^?1. Coated‐grain shoals are less common, whereas crinoidal bars nucleated in well‐circulated settings below wave‐base. Boundstones form a belt (30–300 m wide) at the platform break and interfinger inwards with massive algal‐skeletal wackestones (mud‐rich banks). The progradational phase has divergent outer‐platform strata with basinward dips of 12° to 2°. Steep clinoforms with dips of 20–28° are 650–750 m in relief and possibly sigmoidal to concave in the lower part. The basinward‐dipping outer‐platform strata might be depositional for less than 6°, consistent with lithofacies deepening seaward. The basinward dip is attributed to the downward shift of upper‐slope boundstone, forced by late highstand and relative sea‐level fall, and to compaction‐induced differential subsidence during progradation. The aggradational phase is characterized by horizontally layered platform strata. Clinoforms steepen to 30–45° reaching heights of 850 m and are planar to concave. The evolution from progradation to aggradation, at the Bashkirian–Moscovian boundary, is attributed to increased foreland‐basin subsidence and decreased boundstone accumulation rates. Progradation was primarily controlled by boundstone growth rather than by highstand shedding from the platform top. Within the major phases, aggradational–progradational increments are produced by third‐ to fourth‐order relative sea‐level fluctuations.     

Variable-discharge-river macroforms in the Sunnyside Delta Interval of the Eocene Green River Formation,Uinta Basin,USA

An outcrop dataset from the early Eocene Sunnyside Delta Interval of the Green River Formation in the Uinta Basin, Utah, USA, documents alluvial channel lithosomes. The abundance of Froude supercritical-flow sedimentary structures, together with an abundance of high-deposition-rate sedimentary structures, in-channel bioturbation and pedogenic modification, in-channel muds and thick soft-clast conglomerates, identify these lithosomes as deposits of variable-discharge rivers. These recognition criteria are part of an emerging facies model for variable-discharge rivers. This facies model, however, yet lacks robust recognition criteria for macro-scale or bar-scale stratal patterns of variable-discharge rivers. This study presents a dataset that corroborates some known stratal patterns and provides examples of hitherto unknown bar-scale stratal patterns of variable-discharge rivers, including: (i) low-angle downstream-accretion sets that may form as washed-out sheets in high sediment supply conditions or downstream of hydraulic jumps; (ii) high-angle upstream-accretion sets that imply deposition from systematically upstream-migrating channel-scale hydraulic jumps (cyclic steps); (iii) concave-up, upward-flattening high-angle downstream-accretion sets that are consistent with aggradation in channel-scale hydraulic-jump scours; (iv) upstream-accretion and lateral-accretion sets that may be linked to high-magnitude flood reworking of point bars; and (v) aggradation or vertical-accretion sets of ambiguous origin. These unconventional stratal patterns are compared to the established bar strata, such as those formed by point bars and braid bars and a discussion is provided on formative conditions for the here documented unconventional strata. This work highlights a need for further studies on the effect of discharge variability on bar formation and on the link between river morphology and bar types.     

Marcellus Shale Lithofacies Prediction by Multiclass Neural Network Classification in the Appalachian Basin

Marcellus Shale is a rapidly emerging shale-gas play in the Appalachian basin. An important component for successful shale-gas reservoir characterization is to determine lithofacies that are amenable to hydraulic fracture stimulation and contain significant organic-matter and gas concentration. Instead of using petrographic information and sedimentary structures, Marcellus Shale lithofacies are defined based on mineral composition and organic-matter richness using core and advanced pulsed neutron spectroscopy (PNS) logs, and developed artificial neural network (ANN) models to predict shale lithofacies with conventional logs across the Appalachian basin. As a multiclass classification problem, we employed decomposition technology of one-versus-the-rest in a single ANN and pairwise comparison method in a modular approach. The single ANN classifier is more suitable when the available sample number in the training dataset is small, while the modular ANN classifier performs better for larger datasets. The effectiveness of six widely used learning algorithms in training ANN (four gradient-based methods and two intelligent algorithms) is compared with results indicating that scaled conjugate gradient algorithms performs best for both single ANN and modular ANN classifiers. In place of using principal component analysis and stepwise discriminant analysis to determine inputs, eight variables based on typical approaches to petrophysical analysis of the conventional logs in unconventional reservoirs are derived. In order to reduce misclassification between widely different lithofacies (for example organic siliceous shale and gray mudstone), the error efficiency matrix (ERRE) is introduced to ANN during training and classification stage. The predicted shale lithofacies provides an opportunity to build a three-dimensional shale lithofacies model in sedimentary basins using an abundance of conventional wireline logs. Combined with reservoir pressure, maturity and natural fracture system, the three-dimensional shale lithofacies model is helpful for designing strategies for horizontal drilling and hydraulic fracture stimulation.     

Episodic folding inferred from syntectonic carbonate sedimentation: the Santaren anticline,Bahamas foreland

Sedimentation coeval with growth of the Santaren anticline provides an excellent opportunity to study the relationships between sedimentation and anticline uplift through time. The Santaren anticline is a kilometre-scale, NW–SE trending fold offshore of Cuba, in the Bahamas foreland of the Cuban fold and thrust belt. The growth strata associated with this anticline consist of a thick package of carbonate sediments that were deposited without major interruptions from Neogene (and perhaps before) to present day.The excellent seismic resolution and age control of a number of seismic horizons within the growth strata allowed us to define 25 growth beds, each of them representing between 0.1 and 3.2 Ma. An analysis of the thickness of these beds allowed us to determine accurate quantitative values of cumulative decompacted thickness and crestal structural relief at the time of their deposition. In addition, for the same periods, sedimentation and fold uplift rates were calculated. Moreover, some information on relationships between sedimentation and fold uplift rates was inferred from the growth stratal geometry. Growth beds that overlap the fold crest and thin over it indicate that sedimentation rates outpaced fold growth rates during their deposition. Some overlapping beds have constant thickness indicating that no fold uplift occurred during their sedimentation. The rest of the growth beds exhibit onlap/offlap geometries that do not indicate a unique sedimentation/fold uplift rate relationship. Only in those cases in which the geometry of the underlying bed at the end of its deposition is known is it possible to infer a specific sedimentation/fold uplift rate relationship.As a result of this analysis, we have been able to (1) illustrate that the geometry of the growth strata associated with the Santaren anticline results from competition between sedimentation and tectonic fold uplift, (2) document the episodic and non-steady nature of fold growth, and (3) show that short-term rates (at the scale of hundreds of thousands years) provide much insight into the interplay between sedimentation and tectonic fold uplift that control the growth stratal patterns.     

川南下志留统龙马溪组页岩岩相表征

页岩岩相表征是页岩气地质评价和选层、选区的基础性研究工作。本文以露头和钻井资料为基础,依据岩矿、薄片、地化和测井资料,建立了海相页岩岩相划分方法,对川南上奥陶统五峰组下志留统龙马溪组主要岩相进行了精细表征,并形成4点认识：(1)应用岩石矿物三端员法+沉积微相划分页岩岩相类型及其组合,是开展海相页岩岩相表征的有效方法;(2)川南五峰组龙马溪组页岩发育6种岩相类型和3种典型岩相组合,其中硅质页岩和钙质硅质混合页岩是(半)深水环境的特有岩相,黏土质页岩和黏土质钙质混合页岩是半深水浅水环境的主要岩相,黏土质硅质混合页岩是浅水深水环境下的共有岩相;(3)随着水体由深变浅和水动力条件逐渐增强以及陆源物质输入量增大,不同成因岩相组合的页岩矿物成分、基质组构、古生物和有机质富集程度、测井响应等基本特征均发生重大变化;(4)受海平面变化控制,主力产层为深水陆棚沉积的硅质页岩、钙质硅质混合页岩和黏土质硅质混合页岩组合,产层顶板为半深水浅水陆棚沉积的黏土质页岩、黏土质硅质混合页岩和黏土质钙质混合页岩组合;前者因富含硅质和有机质,具有良好的脆性和物性,是形成页岩气产层的优质岩相;后者因富含黏土和贫有机质,脆性和渗透性差,是形成页岩气藏区域封盖层的优质岩相;两者自下而上构成良好的自封自储型储盖组合。