Through the study of eight well cores from the Upper Permian reefs of Changxing stage in Eastern Sichuan,rocks from Tieshan 5 Well and Tiandong 10 well represent typical sponge reefs;rocks from Bandong 4 Well and Shuanglongchang 15 Well have not only the deposits of reef facies,but also crinoidal or echinoderm banks;rocks from Wolonghe 117 Well,Huanglongchang 1 Well and Yun'anchang 14 Well are mainly composed of carbonate platform deposits;rocks from Dachigan 24 Well consist of two types of reef facies:sponge framework reefs and sponge baffling reefs.Dolomites in the Permian reefs were formed of saline water mixed with fresh water during subaerial exposure of reefs above the sea level,then suffered late dolomitization during deeper burial stage,so they have evident geochemical characteristics of late dolomitization.The original deposits of these dolomites are of framework;not only they could be transformed by reef rocks,but also by those deposits of echinoderm banks,even common carbonate platform depostis.So in finding dolomite reservoirs of reef types,one should pay attention to find dolomite reservoirs formed of bank deposits as well as carbonate platform deposits.

通过川东8口二叠纪长兴期钻井岩芯剖面的详细研究,铁山5井、天东10井代表典型的礁相剖面;板东4井、双15井既有礁相沉积,且有棘屑滩沉积;卧117井、黄龙1井以及云安 14井基本上由碳酸盐台地沉积组成;池24井出现两种类型的礁相 :海绵骨架礁和海绵障积礁。川东礁相剖面中的白云岩以海水与淡水混合作用而成的白云石化为主导因素,但它们在深埋阶段以后,又遭受后期白云石化的叠加,因此表现出许多深埋白云石化的地化特征。白云岩的原始沉积既可能是礁骨架岩,也可能是棘屑滩,甚至是碳酸盐台地沉积。因此在寻找礁型白云岩储层时,还应注意滩相白云岩储层以及一般的碳酸盐台地白云岩储层。

The Lower Permian reefs in the world are distributed in the northwestern Pangean shelf, west slope of the Ural Mountains or eastern margin of the Russian Platform, the Permian Basin of North America and other localities. They occurred mainly in the former two areas. During the earlier period of Early Permian, the reefs were predominated by Palaeoaplysina or Palaeoaplysina-Phylloid algae, but to the later time of Early Permian, the reefs were replaced by Shamovella (Tubiphytes) and bryozoans as their framebuilders. The Early Middle Permian (Qixian Stage) reefs are discovered only in the Glass Mountains of North America, Pamirs and Aerge Mountains in West China. The Late Middle Permian (Maokouan Stage) reefs are regarded as the most well-developed reefs in the world. The Permian reefs of the Guadalupe Mountains become the most classic reefs which exhibit well distinct differentiation of sedimentary facies. The Middle Permian Tunisian reefs have been studied in details. The Middle Permian reefs are characterized by the abundance of sponges, bryozoans and Shamovella (Tubiphytes) as their framebuilders, and Archaeolithoporella, Shamovella and fistuliporids as their binders. The Late Permian reefs in the world occur in the Zechstein Basin of West Europe, western marginal shelf and northern marginal shelf of the Tethys, and some terranes within the Panthalassen ocean. The Late Permian reefs are well developed in South China, which constitutes a bright spot in the distribution of the Permian reefs. These reefs are characterized by coralline sponges, including the sphinctozoans and inozoans as their framebuilders. Archaeolithoporella and Shamovella (Tubiphytes) are usually formed as encrusting and binding organisms.

世界上早二叠世生物礁分布于泛大陆的西北陆棚、乌拉尔山脉的西侧、美国的二叠盆地等地，并集中分布于前两个地区。其早期，以Palaeoaplysina礁或Palaeoaplysina和叶状藻礁占优势，而至晚期则形成以Shamovella (Tubiphytes)和苔藓虫为骨架的礁。中二叠世栖霞期的礁仅发现于北美格拉斯山脉、帕米尔和我国的阿尔格山等地。茅口期的礁是世界上最发育的生物礁之一，北美瓜德罗普山脉的二叠纪礁已成为世界上最典型的礁，其相带分异之清晰堪称为世界之最。北非突尼斯的礁也是研究程度较高的礁之一。中二叠世的礁以海绵、苔藓虫、Shamovella的大量出现为特征，古石孔藻、Shamovella和笛苔藓虫是常见的包覆生物。晚二叠世生物礁分布于欧洲镁灰岩统盆地、特提斯海西缘和最北缘的陆棚以及特提斯海域内的一些地体。我国晚二叠世礁十分发育，成为世界二叠纪礁的一个亮点。礁内的造架生物以珊瑚海绵为主，包括房室海绵和纤维海绵，古石孔藻和Shamovella (Tubiphytes)作为常见的包覆联结生物。

1.Introduction The Upper Permian reefs are widely distributed in Lichuan district,West Hubei,where they are the typical reefs built up by caleisponges and hydrozoan as their frame-building organisms.Their stratigraphical horizon corresponds to Upper Permian Chang-xing Formation.The outcrops of the reefs well expose in Jiantianba,Huangnitang and other localities,Lichuan County.The complete exposure of the reef sequence,the abundance of framebuilding organisms and the distinctness of reef textures and structures make,the Upper Permian reefs in West Hubei become one of the best developed reefs in South China.2.The main features of Jiantianba reef in Lichuan district and its facies or stages of its development or growth.(a)Basin faciesBefore the growth of Upper Permian reefs,the basement for developing the reefs was mainly composed of dark grey and black grey thintomedium bedded spiculitic-calcispherical micrites intercalated with cherty bands and spiculitic siliceous rocks,which represents the typical deposits in deep-water basin.In the basal part,some well-preserved radiolarias have been found.(b)Pore-reef and slope facies or the initial stage of reef growth.Upwards the sediments superimposed represent the initial stage of Upper Permian reef growth,which consists of whitish grey,brown grey thick-bedded and massive sponge-skeletal limestones with the first appearance of f ramebuilding organisms-Sphinctozoa and binding organisms such as blue-green algae and Tubiphytes .In the sponge skeletal limestone some beds of fore-reef slump breccia can be distinguished as thin-bedded layers with wedges intertongued into reef limestone.(c)Reef-core facies Overlying the deposits mentioned above are the sediments of reef-core facies,which represent the most developed stage of reef growth.The reef-core is composed of grey to dark-grey,non-bedded reef-limestones.Organisms found in the reef can be classified into three groups:1) frame builders; 2) binders; 3) accessory organisms.The frame-building organisms are well-preserved Sphinctozoa,Inozoa,Hydrozoan and stromatoporoids.The binding organisms are blue-green algae and Tubiphytes .The accessory organisms including echinoderms,.brachio-pods,gastropods,foraminifers and bryozoan are very rich and often appear as fragments,Here Tubiphytes play an important role in encrusting and binding reef in addition to laminar blue-green algae being in the habit of prominent encrusting.In the reef core,the frame-building organisms or laminar blue-green algae are often surrounded by fibrous calcites,which represent the early cementation of filling the pores within the reefs.In the low burial stage,hypersaline water from lagoonal area seeped into permeable reef area to prompt early forming dolomites outside the fibrous calcite layers.The remaining cavities in the reef were later filled by sparry calcites.It indicates that the interstitial lime mud materials often constitute a greater portion of the reef-debris.These lime muds might be the products of breakage of various organisms,or the products of the bioactivity related to blue-green algae.The frame-building Sphinctozoa and Inozoa are listed as follow: Amblysiphonella,Girtycoelia,Waagenella,Colospongia,Sollasia,Cystauletes,Peronidella,Rhabdactinia .Four new genus,including Lichuanospongia,Polycystocoelia,Sinocoelia,Stromatocoelia ,have been established.The Hydrozoan include the following genus: Palaeoaplysina,Spongiomorpha and others.In the top of the reef-core,the sediments were dolomitized by the interaction of saline water with the fresh water on the superficial exposures of reef and the strong leaching by fresh water.The major deposits are composed of white grey massive medium-crystalline dolomites with remaining echinodermal fragments and other bioclasts.(d)Back-reef faciesThe lagoonal deposits representing the back reef facies are an intercalation of dark grey medium-to-thick bedded echinodermal algal bioclastic limestones with medium-to-thick bedded dolomites and ealcidolomites.The sequences of Permian reef are overlain by the back-reef lagoonal deposits gradually encroached on the reef during the process of progradation of carbonate platform towards the open sea, thus the history of the reef growth eventually ended.Based on the general characteristics of the reef growth development in West Hubei,the reefs exposed in Huangnitang are very similar to those at Jiantianba locality in the same region, but differ from the latter in larger amount of lime mud and less evident encrustine texture formed by fibrous calcites.

鄂西二叠系生物礁分布于利川县境,它是由海绵、水螅等造架生物组成的典型的生物礁,其层位属晚二叠世长兴组,出露于见天坝、黄泥塘等地(图1)。此生物礁从出露之完整、化石之丰富、结构之清楚来看,是我国最发育的生物礁之一。

A comprehensive study of surface geologic, drilling, seismic and other data shows that the Sichuan Basin experienced another extensive regression after the Early Permian, which in combination with the differential elevation and subsidence of fault blocks resulted in the erosion of the Permian Maokou Formation to various degrees and the great change of depositional pattern in the Late Permian. The Kangdian ancient land elevated and enlarged and became the main source area, and the SW-NEtrending deposits of alluvial fanchannel and coalbearing paludal facies were developed successively from land to ocean. To the north and west, the sedimentary facies changed to coastal mixed tidal flat facies along Dayi and Pengxian counties in the foothill belt of Longmen Mountain. Open platform to restricted platform facies consisting mainly of limestone and cherty limestone were developed further north and northeast to many districts like Mianyang, Langzhong, Daxian, Xuanhan, Kaijiang, Kaixian, Wanxian and Yunyang and further east to the western part of Hunan and Hubei provinces. To the north and east of the above sedimentary environment, the Dalong Formation of ocean trough facies dominated by silicic rock was deposited, forming a depositional pattern of several troughs surrounding a platform. Shallow water reefbank of slope facies was developed on the platform margin between the ocean trough and platform. The relationship between the development of reefbank with the rising of water level and the growth of reef building organisms is also analyzed. The large amount of basalt flow blowing out along the submarine rift provided rich SiO2 to the platform and ocean troughs. The reefbank was distributed along the shoulders on both sides of the troughs. Organic oolitic beach was developed on the gentle slope of the platform, while organic reef occurred on the steep slope. The dolomitized reefbank is especially favorable for the accumulation of oil and gas. In the northeastern Sichuan Basin, Bazhong and Yilong lotusform structures are recognized through integrated analysis of the seismic responses of reefbank and the Himalayan and Yanshan tectonism. Fuxingchang, Zhongtaishan and Laojun'an anticlines in relatively stable parts of Mianyang and Zhongtaishan convolute structures may be gas reservoirs of reefbank type.

通过地面地质、钻井、地震等资料的综合研究认为：早二叠世后，四川盆地经历又一次广泛海退，加之断块的差异升降，使二叠系茅口组受到不同程度的剥蚀，晚二叠世沉积格局发生很大变化，康滇古陆上升、扩大，成为主要物源区，沉积相带由陆到海呈南西、北东向展布；依次发育冲积扇—河流，含煤沼泽相环境；向东、向南至自贡、泸州、叙永、古蔺、重庆一带，这套河流相侧变为海陆交互相的滨海潮坪含煤沼泽环境；向北、向西在龙门山前的大邑、彭县一带相变为滨海混积潮坪相；再往北及北东至绵阳、阆中、南充、达州、宣汉、开江、开县、万州、云阳，东至湘、鄂西一线之间发育以石灰岩和燧石灰岩为主的开阔台地到局限台地。在上述沉积环境之北、之东发育硅质岩为主的大隆组海槽相沉积，即广（元）旺（苍）、城口—鄂西海槽，形成多槽围台的沉积格局。在海槽与台地之间的台地边缘，发育斜坡相浅水礁滩环境。分析了礁滩发育程度与水面上升及造礁生物生长的关系，进而认识到礁滩环海槽两侧的肩部分布规律；在台地缓坡发育生物鲕粒滩，在陡坡发育生物礁，尤其是经历白云化作用的礁滩对油气富集有利。在川东北地区采用礁滩的地震响应与喜山、燕山期构造叠合分析，预测了环海槽分布的巴中、仪陇莲花状构造；绵阳旋卷构造、中台山旋卷构造砥柱的复兴场、中台山、老君庵背斜可能是又一个礁滩型气藏。

中上扬子地区上二叠统长兴阶岩石类型主要为碳酸盐岩，其次为碎屑岩和硅岩，还有少量煤和火 山碎屑岩；其岩相可归纳为碎屑岩型、碎屑岩—石灰岩型、石灰岩型、石灰岩—硅岩型、硅岩—碎屑岩型等５ 种类型；其生物化石具４个基本生态类型，可划分为５种化石组合。以沉积岩石学理论为指导，以单因素分析 多因素综合作图法为方法论，选取了厚度、海相岩含量、浅水碳酸盐岩含量、具灰泥基质的生屑含量、具亮晶 胶结的生屑含量、生物礁的分布、薄层硅岩含量和深水沉积岩含量等单因素，对中上扬子地区晚二叠世长兴期 岩相古地理进行研究，编制出了单因素图件８幅，岩相古地理图１幅。研究表明，长兴期岩相古地理格局规律 明显，自西向东依次出现剥蚀区、冲积平原、碎屑岩台地、碳酸盐岩台地、斜坡与盆地，其中碳酸盐岩台地中 可以划分出低能生物滩、高能生物滩和生物礁等次一级的古地理单元；沉积环境对烃源岩的发育具有明显的控 制作用，研究区大隆组优质烃源岩发育；长兴阶储集层以礁相储集层为主，环广元—梁平盆地的台地边缘地区 是长兴组潜伏礁型油气藏的最有利勘探区域。