【作者】 卢刚臣；

【导师】 任建业；

【作者基本信息】 中国地质大学 ， 能源地质工程， 2013， 博士

【摘要】 黄骅坳陷地处渤海湾盆地中心部位,是中-新生代发展起来的叠合型坳陷。前第三纪在经历大规模的挤压为主的构造运动之后,第三纪又遭受拉张为主的正断破坏,进而将黄骅坳陷潜山原构造面貌彻底破坏。坳陷内发育了丰富多彩的逆冲、走滑和反转构造变形样式,其清楚地记录了黄骅坳陷潜山较为完整的构造演化过程。本文以超大面积连片3D及2D地震资料为基础,以沉积盆地动力学和构造地层分析理论和方法为指导,对黄骅坳陷潜山演化历程及展布规律进行系统研究。追踪识别了黄骅坳陷潜山顶界面、侏罗系底界面、中生界底界面、石炭系底界面等重要界面；总结了不同成因类型潜山的平、剖面分布规律,研究了潜山成因成藏要素耦合关系,明确有利潜山类型的展布及其油气藏解剖,梳理出黄骅坳陷有利潜山区带平面图,提出整体部署方案。本文的研究有助于深化对渤海湾盆地潜山演化过程的认识,并对大港探区潜山油气勘探具有指导意义。取得的主要认识和结论如下：1、系统梳理了黄骅坳陷潜山勘探关键构造层,总结出构造层的地震、测井、沉积和构造等综合地质识别特征,建立了黄骅坳陷关键层位追踪的识别技术,识别出潜山勘探关键界面—印支构造面。1)不整合面地震识别与解释技术的总结完善每个层系都有其具体的岩性组合及对应的地震响应特征,根据主要潜山勘探层系地震-地质特征,可开展对不整合面的识别与解释。可分为以下几个步骤：①层位标定先定点。通过该区几口井的标定,确定不整合面的地震特征,再逐渐向整个研究区扩展；②角度剥蚀再浏览。在缺少钻井资料的情况下对潜山的地震资料应进行多方向、多剖面的观察,寻找其中最明显的、分布范围最广的角度不整合面；③上下夹击卡界面。由于不同构造运动产生的地质地震效果不同,在潜山解释中优先解释关键的、最明显的构造运动界面,在此基础上再开展上下夹击卡界面的层位解释与研究,有可能达到事半功倍的效果。2)潜山勘探关键构造层位的识别以往潜山研究主要是基于对潜山内幕几个构造界面的构造闭合建立的构造模型,缺乏对控制潜山演化发育及成藏的关键界面的系统认识。本文在对研究区前第三纪各幕构造运动进行系统梳理基础上,明确印支界面为黄骅坳陷第一个大型角度不整合界面,在地震剖面上“下削上超”现象明显,按照层位标定、上下构造层地震特征对比等易于对该界面进行追踪。其中,印支界面以上的前第三系地层主要包括下、中侏罗统与上侏罗统—下白垩统,前者是在过渡相的沼泽环境下形成的较为稳定的煤层、厚砂层、泥岩交互沉积,地震上表现为中弱振幅夹2-4个中强振幅、连续相位,比较容易追踪,是黄骅坳陷前第三系较重要的勘探层位；后者则表现为中强振幅、不连续地震反射特征。印支界面下部前第三系潜山主要勘探层系为下古生界寒武系、奥陶系(碳酸盐岩储层),上古生界石盒子组(砂岩储层)。寒武系特征由碳酸盐岩夹泥岩组成,表现为强、连续相位(2-3个),特征明显,易于识别、追踪；奥陶系以碳酸盐岩沉积为主,为空白、弱较连续地震反射段,特征明显,区域分布稳定；石炭系以煤系地层沉积为主,地震上表现为3-4个强振幅、连续地震反射相位特征,易于识别、追踪；二叠系为陆相沉积,其内部中-下石盒子组为弱地震反射段,相位较连续,上石盒子-石千峰组泥质含量较高,地震剖面上表现为2个相对较连续相位；三叠系表现为陆相砂泥互层沉积,内部缺少稳定连续反射界面,以空白反射为主。印支界面的解释对深入研究其上、下储层分布、改造和成藏等至关重要,因此印支界面研究不仅完善了盆地构造演化序列,同时更重要的是其可作为古生界、中生界潜山勘探的主要切入点,使潜山勘探更加系统。2、理清了黄骅坳陷潜山构造特征,总结了潜山发育的有利区域—以歧口凹陷为例歧口凹陷潜山构造分布主要受中、新生代构造控制,表现出叠加构造的特点,潜山构造与盆内二级构造带分布并不完全重合。潜山构造分布宏观上受盆内、盆缘隆起(凸起)向凹陷延伸的大型基岩斜坡控制,大体上可以分为四个潜山构造分布区：歧口凹陷西南缘潜山构造区、歧口凹陷南缘潜山构造区、塘沽-新港潜山构造区以及涧南-大神堂潜山构造区。其中西南缘的孔店凸起是分割歧口凹陷与沧东-南皮凹陷的分水岭,也是基底潜山构造发育区。南缘断阶区同样是潜山发育的有利地区,包括埕海和埕北潜山构造带。歧口凹陷北部潜山,即涧南-大神堂潜山构造分布区,主要受沧县隆起基底和涧南凸起基底延伸影响。综上所述,歧口凹陷西南缘、南缘潜山构造最为发育,且由凹陷中心向盆缘的潜山变化呈现规律性,表现为潜山层系逐渐变新,残留古生界逐渐加厚,内幕结构逐渐趋于简单。盆缘潜山主要为中生界断块山和古生界内幕潜山的叠合,凹陷中心发育潜山则是印支期残丘与断块的叠合。3、以古水平面分析法研究古构造埋藏起伏变化作为前提,运用标志性探井的古层拉平和断块恢复技术,结合古地质图及残留地层厚度图开展了潜山形成发育分析。潜山构造解析主要探索基底构造变形过程及其对潜山内幕结构、储层发育的影响。通常,潜山构造演化研究主要采用平衡地质剖面、厚度分析等方法,在古构造恢复的基础上开展演化研究。基于构造演化史分析,结合歧口凹陷前侏罗、前新生代古地质图可以看出,黄骅坳陷歧口地区潜山形成与演化主要与中、新生代三期构造演化有直接关系,分别对应印支期、燕山期和喜山早期。1)印支期构造变形对歧口潜山形成具有重要影响歧口凹陷及周边地区印支期构造变形特点鲜明,体现了华北克拉通裂解初期板内造山、逆冲褶皱的特点。根据恢复的古构造框架图,歧口凹陷前侏罗纪主要表现出向北部抬升的巨型隆起特点。古隆起包括歧口凹陷现今沉降中心和沧县隆起北段的一部分,与南部的复杂向斜构造形成鲜明的对照,围绕古隆起发育“两缓、一陡”古斜坡构造。2)燕山期断裂发育对歧口潜山形成的影响歧口凹陷燕山期构造变形主要从晚侏罗世开始。早-中侏罗纪小型含煤盆地沿印支期古隆起周缘分布,特别是其西南缘地区发育了长轴状古地貌盆地群。晚侏罗世以后,歧口凹陷断裂活动加剧,在印支期古隆起南北两翼出现以大型走滑断层为特征的拉分地堑。3)喜山期差异沉降对潜山形成的影响晚始新世-渐新世,歧口凹陷进入强烈断陷阶段,随沧东断层、赵北-羊二庄断层、茶店断层等盆缘铲式断层活动,歧口凹陷进入翘倾断块演化阶段。受盆内二级断层的控制,歧口凹陷围斜部位出现基底差异沉降演化,形成多个翘倾断块构造,成为半地垒潜山发育的主要因素。该阶段基底变形规模大,已经掩盖了早期潜山的形迹,现阶段落实的潜山构造带主要是喜山期断陷阶段的产物。由于喜山期断陷的作用,歧口凹陷潜山构造最终定型。4、考虑潜山形成机理、潜山内幕结构特点以及成藏基础等地质要素,以成因为主线,将歧口凹陷区潜山划分为3大类12种潜山构造类型第一大类为侵蚀残丘潜山,其是区域不整合和差异风化淋滤作用的直接结果。又根据潜山地层构成、内幕结构特点,将其分为风化壳残丘潜山和内幕残丘潜山两类。前者为内幕结构简单的古地貌潜山,而后者则为内幕存在复杂逆冲断层的地貌潜山,如千米桥潜山。第二大类为走滑-伸展断块潜山,该类潜山由于印支期主要处于斜坡或凹陷地带,古生界顶部不整合面附近未能形成差异风化的地貌潜山,中生界以相对稳定的层序特点覆盖在古生界地层之上。现今潜山山头主要受中、新生代走滑、伸展断层引起的差异升降来完成。按照潜山在盆地中发育的部位、构成地层特点以及断块形态,进一步将其分为两个层系、六种潜山。古生界潜山包括掀斜断块潜山(如港西潜山、羊三木、扣村)、地垒式断块潜山(赵东D区)、伸展滑脱断块潜山(埕海、长芦)和低台阶断块潜山(北桃杏、新港)。中生界层系中发育两种潜山,分别是反向断层控制的鼻状断块潜山和盆缘二台阶断块潜山,这类潜山以埕海东潜山为代表,是典型的构造潜山。第三大类是逆冲型潜山和褶皱潜山。根据潜山内幕特点以及位序特征,又可分为四种类型。即：①大型横弯褶皱潜山,以孔店构造带深部潜山为代表,主要位于沧东断层上盘,由古近纪期间断层相关褶皱控制,顶部堑垒结构明显；②纵弯褶皱潜山,是侧向挤压褶皱的结果,此类潜山在歧口凹陷及周边地区少见,孔店南部东关潜山可以视为该类潜山代表。③伸展改造的背斜潜山,以王官屯潜山为例,早期发育的挤压背斜,被古近纪以来的掀斜断块活动改造而成；④深埋的逆冲褶皱潜山,以乌马营潜山为代表。5、潜山相关成藏要素的研究,明确潜山成藏差异性,指出潜力潜山,指导勘探工作1)潜山油气分布规律从潜山勘探层系上看,奥陶系潜山发现的资源主要为天然气,二叠系和中生界潜山主要为油。从潜山位序来看,高位潜山主要发现侏罗系、二叠系油藏；而中低位潜山则以二叠系、奥陶系气藏为主。规模上看,奥陶系圈闭大,气藏规模较大。而二叠系储量丰度较小,单个潜山探明储量低于50万吨。中生界潜山含油层系多,储层厚度大,单井产量高,是歧口凹陷高潜力潜山。从潜山地质背景来看,也存在一定的规律性。其中。歧口凹陷中发现的奥陶系潜山油气藏主要分布在印支期古隆起及其两翼,现今构造被盆缘铲式断层和盆内二级断层所改造,潜山主要位于现今构造斜坡区和断阶区,高位碳酸盐岩潜山尚未发现油气藏。而二叠系和中生界碎屑岩油气藏则主要分布在基岩断裂交汇的部位,高位潜山垒块构造是主要的油气分布区。2)潜山油气藏形成的关键地质条件歧口凹陷潜山油气成藏主要取决于源储条件,盖层在潜山成藏过程中的影响相对较小。总结了油气成藏的四大特点：其一,两类源岩,形成“新生古储”、“古生古储”两类油气藏。歧口南缘地区石炭-二叠系煤系源岩和孔二段油页岩发育,具备形成原生油气藏的基本条件；其二,古高今低负反转,有利于“新生古储”油气聚集。独特的演化特点,造成歧口凹陷中、低位序潜山构造裂缝密集,风化淋滤储层发育,储盖组合往往优于高位序潜山构造：其三,新近纪深埋藏,潜山圈闭保存条件有利。歧口凹陷大多数潜山圈闭在新近纪以来被深埋在盆地之下,潜山圈闭保存条件相对比较有利；其四,放射状分布的基岩断裂将斜坡区潜山与歧口凹陷主力源岩灶相连,疏导系统较好。综上所述,歧口凹陷潜山油气成藏的关键因素主要有两个：其一是充沛的油气源是形成大型油气藏的关键条件。其中断裂供烃窗口和内幕裂缝系统的发育是决定潜山油气资源规模的重要前提；其二,储层条件至关重要。其中奥陶系碳酸盐岩潜山对储层类型、物性的要求更高。印支期古隆起逆断反转作用显然是导致中、低位潜山物性较好的主要地质因素。更多还原

【Abstract】 Huanghua depression is located in the central of Bohai Bay basin, it is a complex depression dating from Cenozoi., After large-scale extrusion tectonic movement of the Pre-tertiary and tension destruction of the Tertiary, the original structural features of Huanghua depression buried hills were completely destroyed. The tectonic evolution process is clearly recorded by many thrust, strike-slip and inversion tectonic deformation styles in the depression, under the guidance of dynamic sedimentary basins and the tectonic stratigraphic analysis theory and method, this paper make a systematic research on the evolution history and distribution regularities of Huanghua depression buried hills basing on using the mega-sized seismic data of the latest merged-processing. Firstly we track and identify many important stratigraphic interfaces, such as J, Mz and C, then Summarize the distribution regularities of many different genetic types buried hills, and research the relationship between formation and accumulation of buried hills, and make the distribution of better buried hills clearly, at last we put forward the overall deployment plan. This research is good to deepening the understanding of the buried hills’ evolution history in Bohai Bay basin, and also is good to the buried hills oil-gas exploration of Dagang oilfield. The primary understanding and the conclusion is as follows:1、We Tease the key horizons of Huanghua depression buried hills systematically, and sum up the synthetical geological characteristics, including seismic, well logging, Sedimentology and so on, then we identify the key interface—Indosinian structural surface with the key tracking and identification technology.1) the improvement of the sismic recognition and interpretation technologyThey have the different lithological association and seismic response characteristics in different stratas, we do the identification and interpretation in unconformity surface according to the geological and seismic characteristics of the key exploration stratum. It can be divided into the following steps:①horizon correlation.we confirm the seismic characteristics of the unconformity surface by the synthetic seismogram of some wells, then gradually expand to the whole study area;②angular unconformity identification. We should find the more obvious and large angular unconformity by carefully analysising the seismic data because of lacking the enough drilling data.③interface determination. They have the different seismic responses in different tectonic movements, we can interpret the key horizons and the more obvious interface, then broad our horizon interpretation and study to the upper and lower horizon. It may save you a little time.2) the identification of the key horizons of buried hillsThe previous study on buried hills is mainly based on the structural modeling which is built by the interface of inner buried hill, so it is lack of synthetical understanding on the key interface which control the evolution and accumulation of buried hills. This paper confirm that the Indosinian structural surface is a large angular unconformity in Huanghua depression basing on the research on the tertiary tectonic movement, it is shown as truncation and onlaping obviously in the seismic section, it is easy to track by comparing to the upper and lower horizons and the horizon correlation. the pre-tertiary strata above the Indosinian surface mainly include J1+2and J3-K1, the former is the stable coal bed, thick sand bed and mudstone which is formed in the transitional face depositing interactively, it is shown as middle-weak amplitude including two to four middle-strong amplitude, continuous phase, and also is easer to track. It is the important exploration strata of pre-tertiary. The latter is shown as middle-strong amplitude, discontinuous reflection. the pre-tertiary buried hills targets strata below the Indosinian surface mainly include PZ1-∈,O, PZ2-C. the Cambrian is formed by carbonate and mudstone, it is shown as strong and continuous phase obviously, and is easy to identify and track. It is abundant in carbonate in the Ordovician with distributional stability, it is shown as blank or weak, continuous seismic reflection. the main sedimentary formation is coal bed in the carboniferous, it is shown as three to four strong amplitude, continuous reflection, and is easy to identify and track. The Permian belong to continental sedimentation, it is shown as weak, continuous seismic reflection in P1x, it is shown as two continuous phases in P2s and P2sh because of the high shale content. There are mostly blank reflections without continuous reflection in Triassic, it is interbed of sand and shale belonging to continental sedimentation. The interpretation of Indosinian surface is important to deepen the study on reservoir distribution, reconstruction and accumulation. So the study on the Indosinian surface not only improve the evolution series of an basin., but also make it systematic to the buried hills exploration, it wll be an entry path to the buried hills exploration of the Palaeozoic and the Mesozoic.2、In this article we clarified the characteristics of the buried hill structure in Huanghua depression, and summarized the favorable areas for buried hill development,take Qikou Sag for example.The distribution of buried hill structure in Qikou Sag is mainly controlled by Mesozoic and Cenozoic structures, it’s characteristics are revealed as the superposition of structures and it doesn’t coincide fully with the secondary structural belt. On a macro level the distribution of buried hill structure is influenced by bedrock slope, which extends from the uplift of basin inside and basin edge to the sag. Generally it can be divided into four tectonic regions:the southwest of Qikou Sag, southern margin of Qikou Sag, Tanggu-Xingang structure zone and Jian south-Dashentang structure area. The Kongdian high in southwest margin is the watershed, which segments Qikou Sag and Cang east-Nanpi sag. It is also a development zone of the basement buried hill structure. The fault terrace zone in southern margin also is a favorable area of buried hills development, including the buried hill structural belts in Chenghai and Cheng North. The buried hill structure in the north of Qikou Sag, namely Jian south-Dashentang buried hill structure distribution area, is mainly influenced by the basal uplift of county Cang and the extension basal uplift of Jian south.To sum up, the buried hills mainly developed in the southwest margin and south of Qikou Sag. And the regularities presented by the changes from sag centers to the basin edge are the formations are newer, the residual palaeozoic is increasing, and the inside structures gradually tend to simplification. The buried hills in basin edge are mainly the block mountains in Mesozoic and the inside buried hills in Palaeozoic, and the buried hills in the sag center are the composite of Indosinian monadnocks and fault blocks.3、We based on the study on the ups and downs of paleostructure, using the ancient layer flattening technic and block recovery technology, combined with the ancient geological map and residual stratum thickness figure to study the buried hill development.The main purpose of buried hill analysis is to explore the process of the basement tectonic deformation and its influences on the insider configuration and reservoir development. Usually, the evolution research of buried hill structural mainly uses the methods of balance analysis of geological section and the thickness analysis, and on the basis of palaeostructure recovery to study on the evolution. By the analysis of tectonic evolution, combining with the ancient geological map in pre-Jurassic and pre-Cenozoic of Qikou Sag, you can see that the formation and evolution of buried hills in Qikou Sag have a direct relationship with the three tectonic movements in Mesozoic and Cenozoic, they are the Indosinian movement, Yanshan Movement and early Himalayan movement.1) tectonic deformation in Indosinian movement has an important influence on the formation of Qikou buried hills.The tectonic deformation characteristics are bright in Qikou Sag in Indosinian, inside and surroundings, which embody the characteristics of orogeny and thrust fold in early of the north China craton cracking. According to the recovered ancient tectonic frame, Qikou Sag is characterized by the giant uplift in northern uplift zone before Jurassic. Ancient uplift of Qikou Sag includes the current subsidence centre and the north parts of county Cang uplift, which is contrasted brightly with the southern syncline structure. Around the ancient uplift,"two slow, one steep" slope structure developed.2) fracture development in Yanshanian influences on the formation of Qikou buried hills.Yanshanian tectonic deformation of Qikou Sag is mainly starting from late Jurassic. In the early and mid Jurassic small coal bearing basin distribute along the ancient uplift in indosinian, especially in the southwest edge area, forming long axis of the ancient landform basin groups. After the late Jurassic, faulting of Qikou Sag is more strong, large strike-slip faults and grabens appeared in the north and south of ancient uplift in Palaeohigh.3) in Himalayan, the differential settlement influences the buried hill formation.In late Eocene to Oligocene, Qikou Sag is in the stage of fault depression period. The warped fault blocks of Qikou Sag is becoming with the shovel-like faults activity at the edge of Cang east, Zhao north-Yangerzhuang and Chadian. Be controlled by the secondary faults in the basin, the basement evolution of periclinal area in Qikou Sag is differential settlement, forming multiple warped tilting fault block structures, becoming the main factors of the forming of half horst buried hills. In this phase, the large basement deformation already covers the early buried hills. At present, the implementation of the buried hill structural belt is mainly the product of Himalayan fault depression stage. As a result of the action of Himalayan fault depression, buried hill structure of Qikou Sag is in final.4、Considering the formation mechanism, the inside structure and the accumulation condition of buried hills, and following the causes of formation, the buried hills of QiKou Depression are classified into three categories and twelve tectonic types.The first category is called erosion remnant buried hill. It was the direct result of regional unconformity and differential weathering-leaching. According to the formation constitutions and inside architectural features, this category is further divided into two types which are crust weathered-remaining buried hill and inside remnant buried hill. The former type has simple inside structure and the latter has complex thrust fault inside, such as QianMiqiao buried hill.The second category is named strike-slip extension fault block-buried hill. Because of Indosinian movement, this kind of buried hill mainly distributes at the slope or depression. On top of Paleozoic erathem (Pz), differential weathering buried hill was not formed at the unconformity. And the layers of Mesozoic erathem (Mz) deposited stably relatively above the formations of Pz. The buried hills mainly formed due to the differential rise and down which were caused by strike-slip extension fault of Mz and Cenozoic erathem (Kz). According to the location where buried hills lied, the formations which buried hills consisted and the patterns of the fault blocks, this category is further divided into two formations and six types. The buried hills of Pz include tilted fault block-buried hill (e.g. GangXi buried hill, YangSanmu and KouCun buried hill), horst fault block-buried hill (e.g. D Area of ZhaoDong), extension strike-slip fault block-buried hill (e.g. ChengHai and ChangLu), and low bench fault block-buried hill (e.g. the north of TaoXing and XinGang). In the formation of Mz, there developed two types of buried hills which were nosing fault block-buried hills controlled by antithetic faults and second bench fault block-buried hill located at the margin of the basin. These buried hills are typical tectonic buried hills, represented by the buried of ChengHaidong.The third category is thrust-type buried hill and fold-type buried hill. This category is further divided into four subclasses in accordance with the features inside buried hills and the sequence of formations. The four subclasses are as follows:(1) Large bending fold buried hill. This type is represented by the buried hill at the deep tectonic belt of KongDian. It located in the upper wall of CangDong fault and was controlled by the fold which was related to the faults of Paleogene. At the top of the buried hill, garben-horst structures can be seen everywhere.(2) Buckle fold buried hill. It was the result of lateral extrusion, and this type of buried hill is relatively infrequent in QiKou Depression and its surrounding areas. One of the example is the buried hill of DongGuan at the south of KongDian.(3) Anticlinal buried hill remolded by tensile stress. Take the buried hill of WangGuantun as an example. In early stage, it was squeezed anticline, and the movement of tilted fault block turned it into the buried hill now.(4) Thrust fold buried hill. It was buried in deep formations and the typical example is the buried hill of WuMaying.5、Researches of buried hills reservoir-forming controls help our understanding of the difference between the reservoir-forming, affirm the potential reservoir there and guild the further prospecting.(1) Regularity of oil and gas distribution in buried hillsFrom the formations of prospecting in buried hills, the resources discovered in Ordovician are mainly gas, but in Permian and Mz are mainly oil. From the sequence of buried hills, in shallow buried hills, the resources of oil are found mainly in Jurassic and Permian. And in deep buried hill, the resources of gas are mainly found in Permian and Ordovician. From the scale of deposit, the large-scale traps in Ordovician are rich in gas. In comparison the traps in Permian are very poor, and the reserves of each buried hill is less than500,000tons. In the buried hills of Mz, multi-oil measures presented with great thickness, so the production per well is high. Therefore, the buried hills in QiKou Depression occupy the important position in the prospect in this area.From the geological background of buried hills, there is a certain regularity. In QiKou Depression, the resources in the buried hill of Ordovician mainly located at palaeohigh and its two flanks. After that, as a result of the series reform of listric fault at the margin of basin and second-grade fault in the basin, these buried hills now mainly locate at the slope and fault-step zone. And the resources in the clastic rocks of Permian and Mz mainly distributed at the intersection belt of bedrock fracture. So in the shallow carbonate buried hills, no resources were found, but the oil and gas were produced in grievances at almost the same depth. (2) The key conditions for reservoir-forming in buried hillsThe reservoirs of buried hills in QiKou Depression formed depending on the generating and reserving conditions, but the capping rocks played less roll in reservoir-forming. In this thesis, four characters of reservoir-forming are summarized as follows. First of all, two kinds of sources could form two kinds of reservoirs. For one kind of them, the hydrocarbons generated in new formations and reserved in old formations. And for the other kind, the hydrocarbons generated in old formations and reserved there. For example, in southern part of QiKou, there developed much source rocks in Carboniferous and Permian, and also developed much oil shale in Kong-2members. Therefore, all of them constitute the basic conditions for the formation of primary hydrocarbon. Secondly, the depth inversion of old and new formations could also provide conditions for hydrocarbon accumulations. This is the character of unique evolution, and it made the deep buried hill have intensive fractures, undergo weathering-leaching, and develop better reservoir-capping conditions than the shallow buried hills. Thirdly, the formations of Neogene buried deep, which created favorable conditions for capping hydrocarbons in the buried hills. Because in QiKou Depression the majority of traps in buried hills were buried in the basin at that time. Finally, the radial distribution of fractures in bedrocks established good connection between the buried hills in the slope and the major source rocks in QiKou Depression.In conclusion, there are two key factors in reservoir-forming of buried hills in QiKou Depression. One is the abundant sources for hydrocarbons. The important preconditions for the scale of oil and gas reservoirs are the window that fractures provide hydrocarbons and fracture system inside the buried hills. The other is the reserving conditions. In the buried hills of Ordovician, the carbonate rocks required more strict conditions for the types and properties of the reservoirs. The palaeohigh caused by Indosinian movement inversed the thrust faults, and that’s why the properties of the middle and deep buried hills are very good.更多还原