Carbonate Sequence Stratigraphy of a Back-Arc Basin： A Case Study of the Qom Formation in the Kashan Area, Central Iran

The Qom Formation comprises Oligo-Miocene deposits from a marine succession distributed in the Central Basin of Iran. It is composed of five members designated as A-F. Little previous work exists on the sequence stratigraphy. Based on an integrated study of sequence stratigraphy with outcrop data, wells and regional seismic profiles, the Qom Formation is interpreted as a carbonate succession deposited in a mid-Tertiary back-arc basin. There are two second-order sequences (designated as SS1 and SS2) and five third-order sequences (designated as S1-S5). Five distinct systems tracts including transgressive, highstand, forced regressive, slope margin and lowstand have been recognized. The relationship between the sequences and lithologic sub-units has been collated and defined (S1 to S5 individually corresponding to A-C1, C2-C4, D-E, the lower and upper portions of F); a relative sea level change curve and the sequence stratigraphic framework have been established and described in detail. The coincidence of relative sea level change between that of the determined back-arc basin and the world indicates that the sedimentary cycles of the Qom Formation are mainly controlled by eustatic cycles. The variable combination of the systems tracts and special tectonic-depositional setting causally underpin multiple sequence stratigraphic framework styles seen in the carbonates of the back-arc basin revealing: (1) a continental margin basin that developed some form of barrier, characterized by the development of multiple cycles of carbonate-evaporites; (2) a flat carbonate ramp, which occurred on the southern shelf formed by the lack of clastic supply from nearby magmatic islands plus mixed siliciclastics and carbonates that occurred on the northern shelf due to a sufficient clastics supply from the land; and (3) a forced regressive stratigraphic stacking pattern that occured on the southern shelf and in basin lows due to the uplifting of the southern shelf. Thick and widespread aggradational framework limestone usually occurs in the initial sequences (S1 and S3) of the supersequence, which led to preferential oil reservoir deposition but a lack of source and cap rocks, whereas the retrogradational and progradational framework limestone usually occurs in the later sequences (S2 and S4-S5) of the supersequence, which results in two perfect sets of source, reservoir and cap rock assemblies, so that the limestone in sub-member C2-C4 and the F-Member can be predicted as important objects for oil exploration.     

Characteristics of Late Permian Deep-Water Sedimentary Environments： A Case Study of Shaiwa Section, Ziyun County, Guizhou Province, Southwestern China

INTRODUCTIONThe Shaiwa Section is located in the town ofSidazhai, Ziyun County, Guizhou Province, south western China ( Fig. 1 ). This area belongs to theNanpanjiang basin of the Yangtze platform. A greatdeal of work purely on the subdivision of the stratahas been carried out in this region (Guizhou Bureauof Geology and Mineral Resources, 1987). However,studies on recoveries of the paleoenvironments of thisarea are rarely reported. Due to rifting and su…     

Types, Evolution and Pool-Controlling Significance of Pool Fluid Sources in Superimposed Basins： A Case Study from Paleozoic and Mesozoic in South China

Having multiple tectonic evolution stages, South China belongs to a superimposed basin in nature. Most marine gas pools became secondary pools. The pool fluid sources serve as the principal pool-controlling factors. On the basis of eight typical petroleum pools, the type, evolution in time-space, and the controlling of petroleum distribution of pool fluid sources are comprehensively analyzed. The main types of pool fluid sources include hydrocarbon, generated primarily and secondly from source rocks, gas cracked from crude oil, gas dissolved in water, inorganic gas, and mixed gases. In terms of evolution, the primary hydrocarbon was predominant prior to Indosinian; during Indosinian to Yen- shanian the secondary gas includes gas cracked from crude oil, gas generated secondarily, gas dissolved in water, and inorganic gas dominated; during Yenshanian to Himalayan the most fluid sources were mixed gases. Controlled by pool fluid sources, the pools with mixed gas sources distributed mainly in Upper Yangtze block, especially Sichuan (四川) basin; the pools with primary hydrocarbon sources distributed in paleo-uplifts such as Jiangnan (江南), but most of these pools became fossil pools; the pools with secondary hydrocarbon source distributed in the areas covered by Cretaceous and Eogene in Middle-Lower Yangtze blocks, and Chuxiong (楚雄), Shiwandashan (十万大山), and Nanpanjiang (南盘江) basins; the pools with inorganic gas source mainly formed and distributed in tensional structure areas.     

Hydrothermal Mineralization on the Mesoproterozoic Passive Continental Margins of China： A Case Study of the Langshan-Zha＇ertaishan Belt, Inner Mongolia, China

Most ore-forming characteristics of the Langshan-Zha‘ertaishan hydrothermal exhalation belt, which consists of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan large-superlarge Zn-Pb-Cu-Fe sulfide deposits, are most similar to those of Mesoproterozoic SEDEX-type provinces of the world. The characteristics include: (1) All deposits of this type in the belt occur in third-order fault-basins in the Langshan-Zha‘ertaishan aulacogen along the northern margin of the North China Platform; (2) these deposits with all their orebodies hosted in the Mesoproterozoic impure dolomite-marble and carbonaceous phyllite (or schists) have an apparent stratabound nature; ores display laminated and banded structures, showing clear depositional features; (3) there is some evidence of syn-sedimentary faulting, which to a certain extent accounts for the temporal and spatial distribution and the size of the orebodies in all deposits and the formation of intrabed conglomerates and breccias; (4) they show lateral and vertical zonation of sulfides; (5) The Cu/(Pb Zn Cu) ratio of the large and thick Pb Zn Cu orebodies gradually decreases from bottom to top; and (6) barite is interbedded with pyrites and sometimes with sphalerite. However, some characteristics such as the Co/Ni radio of the pyrites, the volcanism, for example, of the Langshan-Zha‘ertalshan metallogenic belt, are different from those of the typical SEDEX deposits of the world. The meta-basic volcanic rock in Huogeqi, the sodic bimodal volcanic rocks in the Dongshengmiao and potassic bimodal-volcanic rocks with blastoporphyfitic and blasto-glomeroporphyritic texture as well as blasto-amygdaloidal structure in the Tanyaokou deposits have been discovered in the only ore-bearing second formation of the Langshan Group in the past 10 years. The metallogeny of some deposits hosted in the Langshan Group is closely related to syn-sedimentary volcanism based on the following facts: most of the lead isotopes in sphalerite, galena, pyrite, pyrrhotite and chalcopyrite plot on both sides of the line for the mantle or between the lines for the mantle and lower crust in the lead isotope composition diagram; cobalt content of some pyrites samples is much higher than the nickel content (Co/Ni= 11.91-12.19). Some volcanic blocks and debris have been picked out from some pyritic and pyrrhotitic ores. All Zn-Pb-Cu-Fe sulfide orebodies in these deposits occur in the strata overlying metamorphic volcanic rocks in the only ore-bearing second formation. In the Jiashengpan deposit that lacks syn-sedimentary volcanic rocks in the host succession only Pb and Zn ores occur without Cu ore, but in the Dongshengmiao, Tanyaokou and Huogeqi deposits with syn-sedimentary volcanic rocks in the host succession Cu ores occur. This indicates a relatively higher ore-forming temperature. The process of synsedimentary volcanic eruption directly supplied some ore-forming elements, and resulted in secular geothermal anomaly favorable for the circulation of a submarine convective hydrothermal system, which accounts for the precipitation of deep mineralizing fluids exhaling into anoxidic basins along the syn-sedimentary fault system in the Langshan-Zha‘ertai rift. The Dongshengmiao, Tanyaokou, and Huogeqi deposits hosted in the Langshan Group appear to be a transitional type of mineral deposit between SEDEX and VMS-types but with a bias towards SEDEX, while the Jiashengpan deposit hosted in the Zha‘ertai Group is of a characteristic SEDEX type. This evidence, together with other new discoveries of Mesoproterozoic volcanic rocks and the features of lithogeny and metallogeny of the Bayun Obo deposit in the neighborhood emphasize the diversity, complexity and uniqueness of the Mesoproterozoic Langshan-Zha‘ertal-Bayun Obo ore belt.     

Periodicity of Element Changes in the Upper Devonian Strata of Dachang Area,Southern China—A Case Study of Spectral Analysis

Power spectral analysis is discussed and an exmple of its application to a geochemical stratigraphic profile is presented.In the Dachang area,all major elements,as well as the maximal sedimentary trend factor(MSTF),demonstrate consistent change periodicity,but are out-of-step with cach other.This can be explained by sedimentogecochemical consideration.The results of power spectral analysis enable geochemists to group elements on the basis of the distribution of their changed periods,and to interpret some special geological and geochemical situations.     

A Middle–Upper Devonian Boundary Section in the Open Platform,Platform Margin Facies of Guilin, South China

Abstract: The Caiziyan Middle and Upper Devonian boundary section is located approximately 30 km northeast of Guilin. It hosts relatively abundant benthic and common–rare pelagic fossils, including brachiopods, corals, tentaculites, and conodonts, which may serve as a better suitable section for pelagic and neritic stratigraphic correlation. In this section, 10 “standard” conodont zones are recognized across the Givetian–Frasnian boundary, including, in descending order, the Lower hassi Zone, punctata Zone, transitans Zone, the Upper falsiovalis Zone, the Lower falsiovalis Zone, disparilis Zone, the Upper hermanni–cristatus Zone, the Lower hermanni–cristatus Zone, the Upper varcus Zone, and the Middle varcus Zone, all of which are defined by the first occurrence of their defining conodont species. The Middle–Upper Devonian (Givetian–Frasnian) boundary is defined by the first occurrence of Ancyrodella pristina in accordance with the Global Stratotype Section and Point (GSSP), which is assigned at 6.2m above the base of bed 19 in the Caiziyan section.     

Characteristics, Formation Periods, and Controlling Factors of Tectonic Fractures in Carbonate Geothermal Reservoirs: A Case Study of the Jixianian System in the Xiong’an New Area, China

As typical carbonate geothermal reservoirs with low porosity in northern China, the Jixianian System in the Xiong’an New Area is the main target for geothermal fluid exploration. The Jixianian System comprises the Gaoyuzhuang, Yangzhuang, Wumishan, Hongshuizhuang, and Tieling formations. The characteristics, formation periods, and controlling factors of reservoir tectonic fractures have been determined based on analyses of outcrops, cores, thin sections, and image logs. The results show that unfilled fractures account for over 87% and most tectonic fractures are high-angle shear fractures with angles concentrated at 40° to 70° and the fracture porosity increases linearly with an increased fracture aperture. Within the same tectonic setting and stress field, the lithology and layer thickness are the dominant factors governing the development of tectonic fractures, which are the most developed in dolomites and thin layers. Tectonic fractures were most likely formed in regions near faults or areas with larger stress gradients. The tectonic fractures in the carbonate geothermal reservoirs are roughly divided into four sets: NNW–SSE and NNE–SSW oriented ‘X’-conjugated shear fractures formed from the Paleozoic to the pre-Yanshanian Movement; NE–SW-oriented shear fractures, formed in episode B of the Yanshanian Movement, occurred at the Early Cretaceous; nearly E–W-oriented tensional fractures formed in the late Yanshanian Movement at the Late Cretaceous to Paleogene, and NEE–SW-oriented shear fractures formed during the Himalayan movement.     

New Technology of Optimizing Heavy Oil Reservoir Management by Geochemical Means：A Case Study in Block Leng 43,Liaohe Oilfield,China

Geochemical methods can be used to optimize heavy oil reservoir management.The distribution of some biomarkers in oils is different with the degree of biodegradation.Geochemi-cal parameters can be used to predict oil viscosity and thus to preliminarily evaluate the difficult-ties involved in oil production.The results of viscosity prediction for oils from reservoir S3^2 in block Leng 43 and preliminary evaluation of oil production difficulty are consistent with the geological data.     

冰川型海平面变化控制下的台地碳酸盐岩成岩作用:以陕西镇安西口石炭-二叠系界线剖面为例

以陕西镇安西口石炭-二叠系界线剖面为具体实例, 探讨了冰川型海平面变化控制下的台地碳酸盐岩成岩作用规律.描述了陕西镇安西口石炭-二叠系界线剖面碳酸盐岩的各种成岩作用类型.根据成岩组构将研究区碳酸盐岩的成岩环境分为海水、大气淡水和埋藏环境.综合分析了各种成岩作用及其成岩环境的纵向分布特征.研究表明, 剖面上碳酸盐岩成岩作用和成岩环境的特征与岩石在高频旋回中的相对位置存在明显的对应关系, 受大振幅、高频率的冰川型海平面变化控制.早期海平面相对上升, 形成旋回的下部单元, 岩石首先经历海底成岩作用, 随着上覆沉积物的增加, 逐渐进入浅埋藏环境, 成岩作用表现为以压溶、重结晶作用发育为主要特征.晚期形成旋回的上部单元, 由于海平面相对下降, 沉积物逐渐抬升, 早期海底成岩作用尚未充分发育就脱离海水环境, 进入大气淡水成岩环境, 以强烈的大气淡水成岩作用为特征.      

陕西镇安西口石炭系-二叠系界线剖面综合地层学研究

对中国海相石炭—二叠系界线典型剖面陕西镇安西口剖面进行了生物地层、层序地层、磁性地层、事件地层多学科综合研究。在石炭—二叠系界线附近建立了4个牙形石生物带,自下而上依次为Streptogna-thoduselegantulus带,S·elongatus带,S·gracilis带和S·isolatus带。将研究区石炭—二叠系界线置于S·isolatus带的底界,较以带Pseudofusulinakrotowisphaeroidea-Dunbarinella(PD)带的底界为标志确定的石炭—二叠系界线层位低3·3m。在西口剖面上石炭统逍遥阶至下二叠统隆林阶,以初始海泛面作为层序界面,识别出12个四级层序(大体相当于副层序组),构成5个Ⅱ型三级层序。这5个三级层序及其对应的海平面变化与贵州独山、罗甸纳水、紫云扁平剖面同期地层中三级层序及海平面变化旋回之间显示出较好的对应关系。除下杨家河阶外,其余各阶的底界,包括逍遥阶、上杨家河阶、范家河阶、垭口阶及隆林阶的底界,基本上都位于沉积相转换点或其附近,即层序地层及海平面变化旋回的关键界面或其附近。表明这5个三级层序的关键界面与年代地层界线的关系相当密切。碳酸盐岩磁化率大小与碳酸盐岩微相存在一定的对应关系,显示相对海平面变化是控制碳酸盐岩磁化率大小的重要因素。另外,在重要地层界线附近常出现磁化率异常高值,说明碳酸盐岩磁化率可能作为地层划分对比的重要依据。西口地区晚石炭世逍遥期至早二叠世隆林期地层中可识别出两次明显的类辐射事件。第一次类辐射事件发生在Occidentoschwagerinaalpina-O·postgallowayi(OS)组合带底部,即下杨家河阶的底部。第二次辐射事件发生在Mccloudiaregularis-Par-aschwagerinafragosa-Robustoschwagerinaxiaodushanica(MPR)组合带底部,即范家河阶的底部。具有三级和三级以上隔壁的四射珊瑚动物群突然大量繁盛,代表四射珊瑚演化进程中一次重大变革。在陕西镇安石炭—二叠系界线附近,这个生物事件首现层位相当于类Pseudofusulinaurdalensi(PU)带下部,高于该带底界不到12m,以Xikouphyllum-Shaannanophyllum-Szechuanophyllum-Wentzellophyllum组合带为代表。在这个层位牙形石也发生了重要变化。各类地质事件记录出现的层位关系密切。在垭口阶底界各类地质事件记录吻合最好,隆林阶底界次之,然后是范家河阶底界。与上述3条界线相比,在镇安西口剖面上,以牙形石Streptognathodusisolatus的首现位置确定的石炭—二叠系界线事件地层特征不明显,既不是一个生物辐射演化面,碳酸盐岩磁化率变化也不太明显,在实际工作中不易使用。     

陕西镇安石炭系一二叠系界线剖面层序地层和相对海平面变化研究

在陕西镇安西口上石炭统逍遥阶至下二叠统隆林阶的剖面上，区分出含生物碎屑灰泥灰岩、生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、生物碎屑颗粒灰岩、团块颗粒灰岩和核形石颗粒灰岩6种主要的碳酸盐岩微相类型。通过详细的微相特征分析，确定了碳酸盐岩沉积过程中的水动力状况和相对水深变化趋势，识别出低能潮下型碳酸盐旋回A1、A2及高能浅滩型碳酸盐旋回B1、B2两类4种高频旋回。根据这些高频旋回在剖面上的有序叠置型式，将镇安西口地区的上石炭统逍遥阶至下二叠统隆林阶划分出12个四级层序和5个Ⅱ型三级层序地层单元，反映了这一地区晚石炭世逍遥期至早二叠世降林期曾发牛过12次四级相对海平面波动和5次明显的三级相对海平面升降。     

陕西镇安石炭系--二叠系界线剖面层序地层和相对海平面变化研究

在陕西镇安西口上石炭统逍遥阶至下二叠统隆林阶的剖面上,区分出含生物碎屑灰泥灰岩、生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、生物碎屑颗粒灰岩、团块颗粒灰岩和核形石颗粒灰岩6种主要的碳酸盐岩微相类型。通过详细的微相特征分析,确定了碳酸盐岩沉积过程中的水动力状况和相对水深变化趋势,识别出低能潮下型碳酸盐旋回A1、A2及高能浅滩型碳酸盐旋回B1、B2两类4种高频旋回。根据这些高频旋回在剖面上的有序叠置型式,将镇安西口地区的上石炭统逍遥阶至下二叠统隆林阶划分出12个四级层序和5个II型三级层序地层单元,反映了这一地区晚石炭世逍遥期至早二叠世隆林期曾发生过12次四级相对海平面波动和5次明显的三级相对海平面升降。     

陕西镇安西口石炭系/二叠系界线剖面碳酸盐岩微相特征与沉积环境的研究

在陕西镇安西口从上石炭统逍遥阶和下杨家河阶到下二叠统上杨家河阶、范家河阶、垭口阶和隆林阶的地层剖面上,区分出10种碳酸盐岩微相类型,即含生物碎屑灰泥灰岩、生物碎屑粒泥灰岩、生物碎屑泥粒灰岩、粒泥灰岩—泥粒灰岩、粗枝藻粒泥灰岩—粗枝藻泥粒灰岩、腕足棘皮粒泥灰岩—腕足棘皮泥粒灰岩、生物碎屑颗粒灰岩、团块颗粒灰岩、核形石颗粒灰岩和含鲕粒团块颗粒灰岩。它们形成于开阔台地和台地边缘浅滩2种沉积环境,开阔台地又进一步分为较浅水的开阔台地浅滩和较深水的开阔台地滩间,台地边缘浅滩内则局部发育藻丘。在此基础上,识别出在晚石炭世逍遥期至早二叠世隆林期研究区发生过12次相对海平面波动,它们构成5次明显的相对海平面升降;最后讨论了三里冲剖面上各阶界线与海平面变化的关系。     

煤山D剖面的放射虫动物群与海平面变化

煤山D剖面长兴组的放射虫动物群的研究成果很少.对煤山D剖面的放射虫动物群进行了详细的鉴定、个体数量和种的数量的统计.结果表明: 煤山D剖面长兴组的放射虫动物群的相对丰度、简单分异度与长兴期海平面变化具有耦合性: 放射虫丰度、分异度较大的层位基本对应于长兴早期和长兴晚期2次最大海侵事件发生的层位.长兴早期放射虫的丰度和分异度较大(相对长兴晚期而言), 这与长兴早期水体相对较深有关.煤山剖面放射虫动物群与海平面变化之间的这种耦合性为海平面变化的研究提供了依据.      

Diagenesis and Restructuring Mechanism of Oil and Gas Reservoir in the Marine Carbonate Formation,Northeastern Sichuan:A Case Study of the Puguang Gas Reservoir

Abstract: Based on the technology of balanced cross-section and physical simulation experiments associated with natural gas geochemical characteristic analyses, core and thin section observations, it has been proven that the Puguang gas reservoir has experienced two periods of diagenesis and restructuring since the Late Indo-Chinese epoch. One is the fluid transfer controlled by the tectonic movement and the other is geochemical reconstruction controlled by thermochemical sulfate reduction (TSR). The middle Yanshan epoch was the main period that the Puguang gas reservoir experienced the geochemical reaction of TSR. TSR can recreate the fluid in the gas reservoir, which makes the gas drying index higher and carbon isotope heavier because C2+ (ethane and heavy hydrocarbon) and 12C (carbon 12 isotope) is first consumed relative to CH4 and 13C? (carbon 13 isotope). However, the reciprocity between fluid regarding TSR (hydrocarbon, sulfureted hydrogen (H2S)?, and water) and reservoir rock results in reservoir rock erosion and anhydrite alteration, which increases porosity in reservoir, thereby improving the petrophysical properties. Superimposed by later tectonic movement, the fluid in Puguang reservoir has twice experienced adjustment, one in the late Yanshan epoch to the early Himalayan epoch and the other time in late Himalayan epoch, after which Puguang gas reservoir is finally developed.     

层序界面对砂岩成岩作用及储层质量的影响——以鄂尔多斯盆地延河露头上三叠统延长组为例

砂岩成岩作用及储层质量是油气勘探的重要研究内容,不同地区砂岩成岩作用及储层质量的主要控制因素各不相同。本文以鄂尔多斯盆地东部延河露头剖面延长组长7上部—长4+5中部三角洲前缘—三角洲平原沉积为例,重点讨论三级层序界面（长16底）上下不同基准面半旋回中砂岩自生矿物、储集空间类型、储集性能和含油性差异及造成这些差异的原因。指出层序界面之下的下降半旋回中浊沸石和早期钙质砂岩结核的发育阻止了绿泥石等粘土矿物及自生石英和自生钠长石的发育,而界面之上的上升半旋回中因凝灰质不足以及地层温度较低造成浊沸石发育有限,加之受湖水影响较小而缺乏早期方解石胶结物,因而绿泥石等自生粘土矿物及自生石英和自生钠长石较为发育,并保留了一部分原生孔隙。层序界面及紧邻其上大规模发育的长16砂体成为流体运移的优势通道,是界面之上浊沸石、方解石胶结物及长石颗粒被酸性流体溶蚀形成次生孔隙的重要因素,也是石油的重要运移通道和储集体。     

断裂控制的非暴露型大气水岩溶作用模式——以塔北Ym2构造奥陶系碳酸盐岩储层为例

岩溶储层在碳酸盐岩储层中占有重要的地位,但过去一直认为表生期碳酸盐岩地层抬升至地表受大气水潜水面控制的岩溶作用是其主要成因.本文在充分认识塔北英买2地区构造地质背景的基础上,通过岩石学、地球化学及其与岩溶成因和控制因素关系的综合分析,提出在地层沉积序列完整的内幕区也可形成大气水岩溶作用改造的缝洞型储层.以岩芯和薄片观察...     

层序格架约束下沉积、成岩作用对岩石物性的控制：以中东A 油田白垩系Mishrif 组为例

厚层块状碳酸盐岩储层垂向非均质性强,层间产液不均衡。为明确储层和隔夹层形成机理和展布规律,以中东A油田白垩系Mishrif组为例,在层序格架的控制下,研究沉积作用和成岩作用对岩石物性的影响。结果表明：Mishrif组内部发育6个四级层序旋回,海平面升降控制了沉积环境演变,并对早期成岩环境具有重要的影响,根据水体能量和成岩作用性质可分为5种沉积—成岩组合：（1）高能沉积环境+建设性成岩作用,滩体发生非选择性溶蚀作用,大幅提高岩石物性形成优质储层;（2）高能沉积环境+破坏性成岩作用,滩体发生不同程度的胶结作用,降低岩石原始物性形成差储层或物性隔夹层,物性隔夹层隐蔽性强,识别困难,加剧了储层的非均值性;（3）低能沉积环境+建设性成岩作用,潟湖、开阔浅海及滩后发生选择性溶蚀和白云化作用,有效改善岩石物性,主要形成差储层;（4）低能沉积环境+破坏性成岩作用,潮湿气候条件下,潟湖相岩石发生压实作用和胶结作用,层序顶部发育炭质泥岩,形成暴露胶结炭化带。干旱和潮湿气候交替条件下,潟湖相岩石遭受多期风化—淋滤,形成致密胶结的角砾岩;该类沉积—成岩组合通常形成于低位体系域,形成稳定分布隔夹层;（5）低能沉积环境+弱成岩作用,岩石原始物性较差,灰泥含量高,后期未发生明显的成岩改造,多形成岩性隔夹层。Mishrif组在多期层序旋回控制下,沉积—成岩组合不断变化,物性隔夹层主要分布在优质储层内部,厚度较薄,规模较小,分布不稳定;岩性隔夹层与差储层相伴生,不同环境中的岩性隔夹层分布稳定性差异较大,致密胶结带通常分布稳定,将地层划分为不同的开发层系。