【作者】 吴娟；

【导师】 叶加仁；

【作者基本信息】 中国地质大学 ， 能源地质工程， 2013， 博士

【摘要】 珠江口盆地是中国南海北部最大的中新生代沉积盆地,也是我国海上重要的油气资源基地。珠一坳陷是珠江口盆地发现油气最多的地区,目前所发现的油田及含油构造主要分布于惠州、恩平、陆丰和西江(番禺4洼)等富烃凹陷及其周边地区,油气资源量占整个珠一坳陷总资源量的62%左右。因此,阐明珠一坳陷尤其是坳陷中已证实富烃凹陷的油气富集规律及主控因素,对低探明地区的油气勘探具有重要的理论指导意义和实际参考价值。本文从珠一坳陷基本地质条件及构造背景出发,综合利用各类地质、地球物理、地球化学资料及相关分析测试手段,在系统分析烃源岩、储集层、盖层、生储盖组合、圈闭等成藏静态要素的前提下,以现代石油地质学、有机地球化学和含油气系统理论为指导,采用静态描述与动态模拟、宏观表征与微观刻画、定性分析与定量计算相结合的综合研究思路及方法,利用有机地球化学方法、流体包裹体分析测试技术和盆地数值模拟手段,剖析了研究区的油气来源、运移动力、输导体系、成藏时间等成藏动态条件及过程,优选了惠西-流花、惠东-陆丰、番禺4洼和恩平南等构造带上的典型油气藏进行综合解剖,在此基础上,总结了珠一坳陷油气在纵向上和平面上的富集规律,建立了不同油气聚集带的油气成藏模式,并阐明了控制油气富集的主要因素。1、油气成藏静态要素利用烃源岩热解数据,结合沉积相分析成果,从有机质沉积环境、丰度、类型和成熟度入手,对比了珠一坳陷文昌组和恩平组两套有效烃源岩的发育特征：文昌组烃源岩为中-深湖相沉积,有机质来源主要为藻类,丰度高、类型好、成熟度高、产油为主,是研究区主要的烃源岩；恩平组为浅湖-湖沼-河流相沉积,有机质来源以高等植物为主,丰度较高、类型稍差、成熟度低-中等,油气兼产,是研究区重要的烃源岩。基于岩心、测井、测试等资料,从岩性、孔隙类型和结构、物性、产能等方面进行分析,将珠一坳陷的储层划分为五种类型：高产油层主要分布于Ⅰ、Ⅱ、Ⅲ类高孔高渗-中孔中渗型储层中；Ⅳ类储层孔渗条件欠佳,主要发育差油气层、油水同层、含油水层以及可疑层；Ⅴ类储层孔渗条件极差,产油极少或不产油。新近系和古近系储层的类型及质量差异较大,新近系海相储层物性好,以Ⅰ、Ⅱ类为主,韩江组和珠江组是研究区主要产层；古近系陆相储层物性明显变差,Ⅰ、Ⅱ类储层减少,Ⅲ、Ⅳ类储层增多,为研究区的次要产层。从宏观展布和微观质量(突破压力、累计厚度、最大单层厚度、盖地比等)两方面对盖层进行评价,确定研究区韩江组、珠江组上段和文昌组发育多套区域性盖层,具有分布范围广、泥岩厚度大、突破压力高的特点,能大范围封盖住油气；珠江组下段、恩平组在大部分地区发育厚层泥岩,可作为地区性盖层,具有较强的封盖能力；珠海组虽然为薄泥多砂地层,但仍发育局部盖层,具有一定的封盖能力。受储层发育及盖层分布控制,研究区自上而下发育珠江组中上段-韩江组下段、珠海组和恩平组、文昌组及前古近系三套储盖组合,目前已发现的大部分油气都分布在上组合中。烃源岩、储集层和盖层在时空上相互配置,形成了自生自储式、上生下储式和下生上储式三种生储盖组合类型,并以下生上储式组合最为常见和重要。珠一坳陷广泛发育多种类型的圈闭,披覆背斜、逆牵引背斜、翘倾构造、断鼻和断块、断背斜等构造型圈闭是目前发现油气最多的圈闭类型,岩性(如砂岩透镜体)、不整合、古潜山、生物礁等地层圈闭是该区实现勘探新突破的重要目标,而构造、地层共同控制的断层-岩性圈闭和构造-岩性尖灭复合圈闭在古近系构造中较为常见。2、油气成藏动态条件及过程根据原油比重和粘度大小,将珠一坳陷的原油划分为两种类型：第一类原油比重低、粘度小,属正常油-轻质油,分布在惠州凹陷的大部分地区和其他凹陷的部分构造中；第二类原油比重高、粘度大,相当一部分为稠油或生物降解油,主要分布在流花油田群和番禺4洼。利用生物标志化合物的生源指示意义,优选了姥植比(Pr/Ph)、C19/C23三环萜烷值、双杜松烷T/αβC30藿烷值和C304-甲基甾烷/C29甾烷值等4个参数,与烃源岩进行对比后,将原油划分为三种类型：第1类原油具有“三低一高”(Pr/Ph值低、C19/C23值低,T/aβC30藿烷值低、C304-甲基甾烷/C29甾烷值高)的特征,与文昌组中深湖相烃源岩有关,对惠西-流花地区、陆丰凹陷、番禺4洼和恩平凹陷的大部分油气藏具有普遍贡献；第Ⅲ类原油具有“三高一低”(Pr/Ph值高、C19/C23值高,T/αpC30藿烷值低、C304-甲基甾烷/C29甾烷值高)的特征,来源于恩平组烃源岩,目前仅在惠州凹陷的HZ9-2构造中发现；第Ⅱ类原油的各项生物标志化合物参数值处于Ⅰ类和Ⅱ类原油之间,为文昌组与恩平组的混源油,分布在环惠州凹陷周边的凸起上以及陆丰凹陷、番禺4洼的个别油藏中。实测地温数据揭示,珠一坳陷现今地温梯度介于2.63-4.33℃/100m之间,平均为3.44℃/100m,整体处于正常地温带。盆地数值模拟结果揭示,研究区古地温场与古热流演化受地幔热流和构造运动控制,具有由高到低、再逐渐升高的变化趋势。在珠江口盆地裂陷阶段,构造活动强烈,地温梯度和热流值较高；盆地后裂陷期,断层活动逐渐减弱,地温梯度和热流值也逐渐降低。通过钻井实测数据、测井声波时差和地震预测的方法,揭示了珠一坳陷现今地层压力的分布情况,结果显示：恩平组以上地层处于正常压实段,压力系数在1.0左右,为常压带；恩平组-文昌组顶部发育低幅度欠压实,压力系数在1.0-1.2之间,为超压过渡带；文昌组中下部地层广泛发育欠压实,压力系数超过1.4,为异常压力带,地层压力分布形态为典型的超压封存箱。恩平凹陷三维地震工区内见到的气烟囱现象也有力的证实了文昌组超压的存在。基于含油气盆地二维数值模拟技术,选取了四条分别经过惠州、陆丰、番禺4洼和恩平凹陷主要生烃洼陷的剖面,进行了古压力场反演,根据反演结果,古地层压力随着沉积沉降或构造运动发生增大→减小→增大的反复循环过程,但总体上显示出增大的趋势,表明了珠一坳陷压力演化的阶段复杂性与总体一致性。珠一坳陷的油气输导体系以断层型为主,兼有不整合型和砂岩(碳酸盐岩)输导层型,油气通过一种类型的通道或多种类型组合形成的复合输导体系进行运移,以后者为主。其中,断层-砂体-断层型输导体系是油气从烃源岩向上构造层运移的主要通道,也是惠州凹陷的油气向东沙隆起运移的重要输导体系类型,断层-不整合型则是油气在下构造层中运聚成藏的主要输导方式。采用储层流体包裹体分析法,通过包裹体显微观测、荧光光谱分析、均一温度测定等,确定珠一坳陷总体经历过两期油气充注,时间分别为中中新世韩江组沉积时期和晚中新世粤海组沉积时期,以第二期充注为主。不同层位上,从文昌组到珠江组,两期油气充注时间均有逐渐变晚的趋势,珠江组上段仅经历过一期油气充注,东沙运动前后为油气成藏的关键时期,新近系很多油气藏都是在这个时候形成的,表现为晚期多层同注的特点。3、油气富集规律及主控因素选取珠一坳陷不同构造区带上的典型油气藏,对油气成藏条件、成藏过程进行综合解剖,探讨了各油气藏的形成机制和控制因素。在此基础上,总结了研究区油气在纵向上和平面上富集的规律：纵向上具有多层含油、分段富集的特征,油气分布井段长,但主要聚集在韩江组下-珠江组的上组合中；平面上呈差异分布、群带富集的特点,惠州凹陷以惠西-流花和惠东-陆丰两条油气聚集带最为富集,番禺4洼的油气围绕生烃洼陷呈环带状富集,恩平凹陷的油气则主要富集在南部隆起断裂构造带上。综合考虑油气来源、输导体系和成藏期次,将惠西-流花油气聚集带的油气成藏模式归纳为四种类型：单源-垂向运移-多期成藏模式、混源-垂向运移-多期成藏模式、混源-垂向-侧向运移-多期成藏模式以及单源-侧向-垂向运移-多期成藏模式；惠东-陆丰油气聚集带的模式为单源-侧向-垂向运移-多期幕式(快速)成藏模式;番禺4洼油气聚集带为单源-垂向-侧向-一期成藏模式；恩平南部油气聚集带的成藏模式归纳为单源-侧向-垂向-一期成藏模式。综合分析各项成藏静态要素及动态条件与过程,阐明了控制珠一坳陷油气富集的主要因素：生烃洼陷决定油气富集程度；输导体系控制油气运移范围；构造部位制约油气聚集能力；储层条件影响油气储量大小。更多还原

【Abstract】 The Pearl River Mouth Basin is the largest Mesozoic-Cenozoic sedimentary basin in the northern South China Sea, and is also an important oil and gas resource base in offshore China. Among it, the Zhu I Depression has been confirmed to be the region with the best commercial exploration results. Previously discovered oilfields and oil-bearing structures are mainly distributed in the hydrocarbon-rich sags of Huizhou, Enping, Lufeng and (Panyu4Sag) and its surrounding areas, these oil and gas resources account for about62%of the total resources in the Zhu I Depression. Therefore, carrying out research on hydrocarbon accumulation regularity and the master control factors of the confirmed hydrocarbon-rich sags in the Zhu I Depression will provide some theoretical revelations and practical reference value for low proved oil and gas exploration areas.Starting from the basic geological conditions and tectonic background of the Zhu I Depression, based on the comprehensive utilization of the data and techniques of geology, geophysics and geochemistry and under the guidence of multi-disciplinary theories, this paper studied firstly the static elements of hydrocarbon accumulation such as source rock, reservoir, seal rock, source-reservoir-seal assemblage and trap, systematically. Using the combination research approachs of static description and dynamic simulation, macro and micro features, qualitative analysis and quantitative calculation and taking the techniques of organic geochemistry, fluid inclusions analysis and basin numerical simulation, this paper analyzed the accumulation dynamic conditions and process such as oil and gas source, migration dynamics, the conduit system, accumulation time deeply. And chosen some typical reservoirs in the Huixi-Liuhua, Huidong-Lufeng, Panyu4Sag and south Enping as comprehensive oil and gas reservoir anatomy targets. After that, the rules of oil and gas accumulation regularity in the Zhu I Depression vertically and laterally was summarized, oil and gas accumulation model in the different oil and gas accumulation zones was established and the main control factors of oil and gas accumulation was expounded.1. The static elements of hydrocarbon accumulationBased on the source rock pyrolysis data, began with sedimentary environment, organic matter abundance, types and maturity analyses, this research compared the characteristics of the two sets of effective hydrocarbon source rock (Wenchang group and Enping group) in Zhu I Depression:The sedimentary facies of Wenchang source rock is medium-deep lake and the major source of organic matter is algae. With the characteristics of high abundance, good types, high maturity, maily oil production, Wenchang source rock is the main hydrocarbon source rocks in the study area;The sedimentary facies of Enping source rock is shallow lake-lake-fluvial facies, and the major source of organic matter is higher plants. With the characteristics of high abundance, relatively poor type, low to medium maturity, and oil and gas production, the Enping source rock is also serves as important hydrocarbon source rocks in the study are. According to the core, logging, testing and a great quantity of other data, the reservoirs in Zhu I Depression are divided into five categories after the study of lithology, physical properties, pore types and structure, capacity and other factors of the reservoir:prolific oil layers mainly distributed in the reservoirs Ⅰ, Ⅱ and Ⅲ which have high porosity and permeability or medium to high porosity and permeability; reservoir Ⅳ has poor porosity and permeability, mainly with the found of poor oil and gas layer, oil and water layer, oily water layer and suspicious layer; IV category reservoir has extremely poor poroperm characteristics with few oil produced or no oil produced at all; The difference between the categories and qualities of the Neogene and Paleogene reservoirs is significant, the Neogene marine reservoir has high porosity and permeability, mainly belong to Ⅰ or Ⅱ reservoir categories, Hanjiang group and Zhujiang group are chief pay zones in the study area; The poroperm characteristics of Paleogene reservoir deteriorate obviously with lower proportion of Ⅰ, Ⅱ categories reservoirs, more Ⅲ, Ⅳ categories reservoirs, serve as secondary pay zones in the study area.Under the evaluation of the seal rock’s macroscopic distribution and microscopic quality (breakthrough pressure, the cumulative thickness, ratio of maximum thickness of single layer, mudstone ratio, etc.) several sets of regional seal rock in the Hanjiang group, upper Zhujiang group and Wenchang group in the study area are confirmed, with the features of widely spread, large thickness of mudstone, high breakthrough pressure, which can sealing the oil and gas effectively; The latter Zhujiang group and Enping group developed thick mudstone in most areas, which can be used as regional seal rock with the effectively ability of sealing; although the Zhuhai group is thin and sandy, it still has certain ability of sealing with the local seal rock developed. Controlled by the distribution of reservoir and seal rock, the study area developed three sets of reservoir-seal associations(upper middle Zhujiang group-latter Hanjiang group, Zhujiang group-Enping group, Wenchang group-former Palaeogene) vertically, at present most of the oil and gas distribution in the three reservoir-seal associations. Source rocks, reservoirs and seal rocks have matching relationship between spatial and temporal, which has formed three categories of source-reservoir-caprock associations (self sourced reservoirs, source rocks in the upper part and reservoirs in the lower part, associated with source rocks in the lower part and reservoirs in the upper part), and source rocks in the lower part and reservoirs in the upper part is the most common type found. Zhu Idepression has developed multiple types of traps widely, such as drape anticline traps, reverse drag anticline traps, tensile-tilting tectonic, fault nose and fault block, ect. Tectonic traps like faulted anticline are traps that found mostly prolific. Stratigraphic traps like lithology (such as sandstone lens), unconformity, buried hill, biological reef, ect., have great exploration potential, which is a fine exploration main battlefield of achieving new breakthrough in this area. However fault-lithologic trap and structure-lithology pinchout combination trap are more common in the Paleogene stratum.2. Dynamical conditions and process of hydrocarbon accumulationAccording to crude oil density and viscosity, the crude oil in ZhuIdepression could be divided into two types:The first kind of crude oil has low weight, low viscosity, belongs to the normal to light oil, distributed in most parts of Huizhou Sag and the other structures in sags else; The second category crude oil has high density, high viscosity with a considerable part of heavy oil or biodegraded oil, mainly distributed in Liuhua oilfield group and Panyu4Sag. Thanks to the indicating of biomarkers, Pr/Ph, C19/C23tricyclic terpane, double juniper alkanes T/αβC30hopane and C304-methyl/C29sterane were optimized as four effective parameters, after compared with hydrocarbon source rock, crude oil is classified into three types:category Ⅰ crude oil with "three low and one high"(low Pr/Ph and low C19/C23, low T/a(3C30hopane, high C304methyl/C29sterane) features, related to deep lake facies source rocks in Wenchang group, and play an important role to most of the oil and gas reservoirs in the Huixi-Liuhua region, Lufeng Sag, Panyu4Sag and Enping Depression; category Ⅲ crude oil has "three high one low"(high Pr/Ph, high C19/C23, low T/αβC30hopane, high C304-methyl/C29) characteristics, coming from the hydrocarbon source rocks of Enping group, currently only found in HZ9-2structure of Huizhou Sag; category II crude oil has relatively medium biomarker values between category I and II crude oil, regarded as a mix of Wenchang and Enping oil, distributed on part of oil pools in the convex ring around Huizhou Sag, Lufeng Sag and Panyu4Sag. Measured temperature data revealed that geothermal gradient in Zhu I Depression is between2.63-4.33℃/100m now, with an average of3.44℃/100m, belong to normally temperate zone overall. From the basin numerical simulation results, it can be seen that the ancient ground temperature field and heat flow in the study area is controlled by the mantle heat flow and tectonic movement change, with a fluctuate trend of high to low then gradually rising. The results also revealed that there is strong tectonic activity, high geothermal gradient and high heat flow during the chasmic stage in Pearl Mouth Basin; However, in the late chasmic stage, the fault activity weakened gradually with geothermal gradient and heat flow values reduced as well. Using the drilling test, AC well logging data, combining seismic prediction together, the distribution of formation pressure nowadays in Zhu I Depression is revealed. According to the results, The groups above Enping group has normal compaction with pressure coefficient of around1.0, belong to normal pressure zone; the top of Enping-Wenchang group developed low amplitude under compaction with pressure coefficient between1.0-1.2, belong to overpressure transition zone; The latter Wenchang formation developed under compaction widely with pressure coefficient exceeds1.4, belong to abnormal pressure zone, typical overpressure compartment. Gas chimney phenomenon identified from the three dimensional seismic data of Enping Depression also powerfully proved the existence of the overpressure in Wenchang group. Based on the two-dimensional numerical simulation technology, four hydrocarbon generation profiles of Huizhou, Lufeng, Panyu4Sag were selected to study the ancient stress field, the inversion results revealed that the formation pressure experienced a repeatedly progress of increase-decrease-increase, but generally showed an increasing trend as a whole, which illustrated complexity and overall consistency of pressure evolution in the Zhu I Depression. The oil and gas transportation systems in Zhu I Depression mainly belong to fault type, partly belong to unconformity and sandstone type (carbonate rock) conducting layer. Oil and gas migrated mainly through composite passage system which has various passage way combined rather than through single passage. Among passage systems, the fault-sand-fault passage system is the main passage for oil and gas migrate upward from source rock to the reservoir, it also is an important passage system for the gas and oil in the Huizhou Sag move to Dongsha uplift and fault-unconformity passage system play a significant role in oil and gas migration and accumulation in the latter stratums. With the help of reservoir fluid inclusion analysis, the research on inclusion microscopic observation, fluorescence spectrum analysis and determination of uniform temperature showed that the Zhu I Depression generally experienced two phases of oil and gas filling, in the medium Miocene epoch and the late Miocene epoch respectively, the later filling phase is the relatively more important one. From Wenchang group to the Zhujiang group, the two phase of oil and gas filling both have a trend of gradually late, the upper Zhujiang experienced only one phase of oil and gas filling, Dongsha movement is a critical period of hydrocarbon accumulation, many Neogene reservoirs were formed at this time, as many layers filled at the same with the later period. The master control factors of oil and gas accumulation regularity Typical reservoirs has been selected from different tectonic belt in Zhu I Depression, and its conditions and processed of hydrocarbon accumulation were comprehensive analyzed. Then, the formation mechanism and control factors of oil and gas reservoirs were discussed.3. Enrichment regularity and main controlling factorsOn the basis of this, the accumulation regularity of oil and gas in the study area are summarized vertically and laterally:On vertical, the oil and gas mostly gathered in the combination of latter Hanjiang group-upper Zhujiang group; On lateral, the oil and gas accumulated showed zonal differences, Huixi-Liuhua and Huidong-Lufeng are the best oil and gas accumulation zone in Huizhou Depression; Panyu4Sag has oil and gas distribute circularly around the generating hydrocarbon sag; However, oil and gas in Enping Depression are largely distribute in the bulge-fracture tectonic belt in the south. According to the petroleum source, passage system, hydrocarbon migration direction and pool-forming period, the modes of hydrocarbon accumulation in Huixi-Liuhua oil and gas accumulation zone could be sum up into four patterns:unisource-vertical migration-multiphase accumulation pattern, mixed source-vertical migration-multiphase accumulation pattern, mixed source-vertically&laterally migration-multiphase accumulation pattern and unisource-vertically&laterally migration-multiphase accumulation pattern; The hydrocarbon accumulation pattern in Huidong-Lufeng oil and gas accumulation zone is unisource-vertically&laterally migration-multiphase accumulation (fast); The hydrocarbon accumulation pattern in Panyu4Sag is unisource-vertical&lateral migration-single period accumulation pattern; The hydrocarbon accumulation pattern in south Enping Depression is unisource-vertically&laterally migration-single period accumulation pattern.After comprehensively analyzed the various factors of static element and dynamic conditions of hydrocarbon accumulation, the most important control factors of hydrocarbon accumulation in Zhu I Depression is illustrated:The degree of hydrocarbon accumulation is decided by the generating hydrocarbon depression, the scope of oil and gas migration is controlled by the passage system and the ability of oil and gas gathering is restricted by the tectonic position, reservoir conditions affect the size of the oil and gas reserves.更多还原