南海珠江口盆地深部烃类微渗漏的分子地球化学揭示

对南海珠江口盆地Site4B站位柱状沉积物可溶有机质中正构烷烃进行详细分析,结果显示海底以下65~70cm、80~85cm和85~90cm存在明显的似成熟烃类分布。在气相色谱质谱图上(GCMS),该处存在明显的UCM分布;在烃类分布上,该处以可溶有机质中高碳数正构烷烃奇偶优势趋于消失为特征,CPI为1.15~1.45。同时,整个剖面其他层段沉积有机质中可溶烃类仍以典型的近/现代沉积有机质输入为标志。结合区域地质背景,以及该区域天然气水合物的勘探发现事实,推断Site4B站位海底以下65~70cm、80~85cm和85~90cm烃类异常可能系深部烃类微渗漏所致。     

珠江口盆地第三纪古地理及沉积演化

珠江口盆地第三纪以来经历了断陷、拗陷两个构造演化阶段,具有“南北分带”、“东西分块”的构造格局和先陆后海的沉积特征。本文根据前人资料进行综合整理,编制了珠江口盆地古近纪神狐组、文昌组、恩平组、珠海组地层和新近纪珠江组地层的岩相古地理图。神狐组发育有冲积扇和河湖相,主要分布在珠三坳陷南断裂的狭长地带。文昌组沉积半深湖—深湖相,恩平组水深变浅,河沼相广泛分布。珠海组岩相古地理发生了较大的变化,为海陆过渡相沉积。随后海平面振荡上升,珠江口盆地处于陆架—陆坡环境,发育浅海—半深海沉积。对整个珠江口盆地岩相古地理图的编制为详细研究盆地内各区块的岩相古地理演变提供了区域背景,也为区域构造演化和油气地质条件的研究提供了基础依据。     

南海珠江口盆地深水区混合沉积类型及其形成机制

珠江口盆地是研究深水沉积过程和南海油气勘探的热点区域。利用地震、测井和钻井岩屑等资料,发现珠江口盆地深水区晚渐新世至中中新世期间,发育混合沉积体系。该混合沉积体系岩相主要表现为碳酸盐岩与硅质碎屑以不同比例的混合堆积,垂向岩相变化存在突变式、渐变式和交互式三种递变类型。根据地震反射以及岩相特征,混合沉积体系可划分为4个沉积阶段：第1阶段主要为原位混合沉积,形成渐变式或突变式混合沉积;第2阶段为相缘混合,产生渐变式混合沉积层系;第3、4阶段为间断混合,形成交互式混合沉积。在硅质碎屑沉积为主的背景下,混合沉积由于碳酸盐碎屑的加入,可能会形成潜在的油气储层,对今后深水油气勘探有一定的启示意义。     

南海北部珠江口盆地深水区碳酸盐岩发育特征及地震识别

由于南海的多次扩张、拉伸、消减运动,在珠江口盆地白云深水区发生了陆架裂陷和海水入侵等地质现象,形成了海相碳酸盐岩生长发育的基础地质条件。对珠江口盆地深水区碳酸盐岩的发育地质背景、地质特征、发育规律、地震响应特征以及深水区灰岩发育的主控因素进行了探讨,结果表明白云深水区主要发育两种类型的碳酸盐台地;古隆起镶边台地以及火山建隆孤立台地。台地沉积主要发育在古隆起周缘、构造高部位、火山隆起周缘,并被钻井所证实。在白云深水区东沙隆起西南缘、云荔低凸起、荔湾凹陷北缘、荔湾凹陷南缘及顺鹤隆起发育典型的生物礁,钻井证实有珊瑚、红藻、苔藓虫等造礁生物。生物礁地震特征具有强的连续反射顶、底界面,丘状反射外形,内部结构或空白、或杂乱,具有前积、加积、退积等层序结构。     

珠江口盆地西部新近纪高分辨率生物地层及海平面变化分析

珠江口盆地西部新近系主要为陆架浅海沉积环境,发育良好的海相砂岩储集层和多套储盖组合。因此,对这些砂体的成因及赋存位置的海平面变化研究至关重要。在有孔虫及钙质超微化石资料所建立的珠江口盆地西部新生代年代地层格架基础上,以有孔虫个体大于0.25mm的浮游有孔虫丰度和百分含量为依据,参照微体古生物化石带、岩性、电测和地震资料,总结出三级旋回边界和最大海泛面识别标志,从而提出具有国际对比意义的三级层序划分对比方案,对盆地内18口井进行了层序划分,识别出了2个完整的二级层序和15个三级层序。根据南海海域表层沉积物建立起的浮游有孔虫含量与水深的定量关系,得出量化古水深数据,辅以古生态成因相及特征沉积构造分析、海岸上超分析编制了海平面变化曲线,指出珠江口盆地西部新近系受拗陷阶段持续沉降影响,形成不同于海退型全球海平面变化的台阶式海侵特征。     

南海北部陆坡珠江口盆地东南海域GMGS2-09井孔隙水地球化学特征及其对天然气水合物的指示意义

沉积物孔隙水地球化学是天然气水合物勘探与研究的重要手段。为了探究珠江口盆地东南海域GMGS2-09钻孔的沉积物孔隙水地球化学特征及其对埋藏的天然气水合物的指示意义,我们在前人的研究和认知基础上,通过测试该钻孔沉积物孔隙水的氯离子含量、氢氧同位素和阳离子组成来识别天然气水合物的赋存层位。结果表明GMGS2-09钻孔在9~17、47以及100m处存在氯离子浓度的负异常耦合氧同位素的正异常,指示相应的天然气水合物赋存,其中9~17m层位指示结果与实际取样情况完全一致。此外,采用基于水合物晶格的排盐机理推导的经验公式计算显示水合物饱和度在浅表层(17m)最高约为50%,中间以及底层约为20%。     

Seismic geomorphology,architecture and genesis of Miocene shelf sand ridges in the Pearl River Mouth Basin,northern South China Sea

Multiple stages of large-scale shelf sand ridges, including the shoreface-attached and the offshore types, have developed in the Miocene successions on the mid-shelf region of the Pear River Mouth Basin, northern South China Sea. Utilizing a high-quality 3D seismic data set, accompanying 2D seismic profiles and well logs, the morphology, architecture and genesis of these shelf sand ridges have been systematically investigated in this study. The ridges are of very large scale, with the largest one having a maximum height of 64 m, a width of more than 20 km and a length of 37 km within the 3D survey area. Being mound-shaped, they also display obvious asymmetry character, with the ridge crest preferentially located on the SE side. Three main internal components, including the ridge front, central ridge and the ridge tail, have been recognized through careful anatomy analysis of the two most well-imaged ridges, each displaying distinct expressions on seismic amplitudes and geometries. In the plan view, most of the shelf sand ridges are generally NE–SW oriented and widening to the SW direction. Scouring features can also be clearly observed along the SW direction, including scour depressions and linear sandy remnants. On well logs, the shelf sand ridges are represented by an overall coarsening-upward pattern. Intervals with blocky sandstones are preferentially present on higher locations due to a differential winnowing process controlled by shelf topography.Plenty of evidence indicates that these ridges were primarily formed by the reworking of forced regressive or lowstand deltaic deposits under a persistent southwesterly flowing current during the subsequent transgression. This very current is a composite one, which is speculated to consist of winter oceanic current, SCSBK (South China Sea Branch of Kuroshio) intrusion onto the shelf and internal waves propagating from the Luzon Strait. Tidal currents might have contributed to the SE growth of the ridge. In response to the reglaciation of Antarctic ice-sheet and the closure of Pacific-Indian ocean seaway in the middle Miocene, the intensification of the North Pacific western boundary current was considered to have potential links to the initiation of the shelf sand ridges at ∼12 Ma. The development of shelf ridges was terminated and replaced by rapid deltaic progradation at ∼5.5 Ma.     

Geochemistry,origin, and accumulation of petroleum in the Eocene Wenchang Formation reservoirs in Pearl River Mouth Basin,South China Sea: A case study of HZ25-7 oil field

The Pearl River Mouth Basin in the South China Sea has accumulated >2 km of Eocene sediments in its deep basin, and has become the exploration focus due to the recent discoveries of the HZ25-7 oil field in the Eocene Wenchang (E₂w) Formation. In this study, the geochemical characteristics of potential source rocks and petroleum in the HZ25-7 oil field are investigated and the possible origins and accumulation models developed. The analytical results reveal two sets of potential source rocks, E₂w and Enping (E₂e) formations developed in the study area. The semi-deep-to-deep lacustrine E₂w source rocks are characterized by relatively low C₂₉ steranes, low C₁₉/C₂₃ tricyclic terpane (<0.6), low C₂₄ tetracyclic terpane/C₃₀ hopane (<0.1), low trans-trans-trans-bicadinane (T)/C₃₀ hopane (most <2.0), and high C₃₀ 4-methyl sterane/ΣC₂₉ sterane (>0.2) ratios. In contrast, the shallow lacustrine and deltaic swamp-plain E₂e source rocks are characterized by relatively high C₂₉ steranes, high C₁₉/C₂₃ tricyclic terpane (>0.6), high C₂₄ tetracyclic terpane/C₃₀ hopane (>0.1), variable yet overall high T/C₃₀ hopane, and low C₃₀ 4-methyl sterane/ΣC₂₉ sterane (<0.2) ratios. The relatively low C₁₉/C₂₃ tricyclic terpane ratios (mean value: 0.39), low C₂₄ tetracyclic terpane/C₃₀ hopane ratios (mean value: 0.07), high C₃₀ 4-methyl sterane/ΣC₂₉ sterane ratios (mean value: 1.14), and relatively high C₂₇ regular sterane content of petroleum in the HZ25-7 oil field indicate that the petroleum most likely originated from the E₂w Formation mudstone in the Huizhou Depression. One stage of continuous charging is identified in the HZ25-7 oil field; oil injection is from 16 Ma to present and peak filling occurs after 12 Ma. Thin sandstone beds with relatively good connectivity and physical properties (porosity and permeability) in the E₂w Formation are favorable conduits for the lateral migration of petroleum. This petroleum accumulation pattern implies that the E₂w Formation on the western and southern margins of the Huizhou Depression are favorable for petroleum accumulation because they are located in a migration pathway. Thus exploration should focus in these areas in the future.     

珠江口盆地前新生代先存断裂特征及动力背景

前人针对珠江口盆地前新生代开展过大量研究,但对盆地的原始构造格局仍缺乏统一认识。在高精度三维地震资料的基础上,笔者采用“定性+定量”先存断裂综合识别技术,识别出珠江口盆地惠州凹陷和番禺4洼前新生代基底发育的先存断裂583条。按照断裂是否断穿Tg和断裂倾角大小,将先存断裂分为4类：高角度节理、低角度节理、高角度活化断层和低角度活化断层;按断裂走向划分,将先存断裂分为NW-NWW向和NE-NEE向2组。燕山期晚侏罗—早白垩世,古太平洋板块对华南板块沿NW向正向俯冲,形成NE-NEE向逆冲断裂;燕山期晚白垩世,古太平洋板块对华南板块斜向俯冲产生左旋挤压应力场导致NW-NWW向逆冲断裂形成。这些先存断裂从源头上控制了珠江口盆地的构造格局,为研究盆地后续演化提供了重要支撑。     

珠江口盆地陆丰凹陷古近系储层特征及优质储层主控因素

随着珠江口盆地勘探层系由浅层转向深层,古近系已成为陆丰凹陷油气“增储上产”的重要层系,但储层尚存在非均质性较强、产能释放难度大等问题,严重制约油气勘探进程。综合运用陆丰凹陷36口古近系钻井的铸体薄片、扫描电镜、物性分析、X衍射等分析化验数据,对文昌组和恩平组开展储层特征、成岩作用和优质储层主控因素研究。结果表明,陆丰凹陷古近系储层具有高石英、低长石和低岩屑含量的特征,文昌组主要发育岩屑石英砂岩,为特低—低孔隙度、超低—低渗透率储层,平均孔隙度为11.15%,平均渗透率10.93×10−3 μm2;恩平组主要发育长石石英砂岩,为低—中孔隙度、特低—中渗透率储层,平均孔隙度为15.23%,平均渗透率为139.53×10−3 μm2;储层孔隙类型以原生粒间孔为主,其次为粒间溶孔和粒内溶孔,但文昌组溶蚀孔占比高。古近系储层主要处于中成岩阶段A期,压实作用对减孔起决定性作用,胶结作用降低储层物性,溶蚀作用进一步改善储层物性。陆丰凹陷古近系优质储层形成条件包括：①母岩区石英含量高,搬运距离较远,高成分和结构成熟度,杂基含量低,单层砂体厚度大;②强流体改造改善储集空间,长石溶蚀对古近系尤其是文昌组储层改善明显,拥有良好断裂沟通源岩或临近源岩的砂岩储层溶蚀作用强;③凝灰质充填导致储层渗透率降低,低火山活动影响区更有利于优质储层发育。     

珠江口盆地恩平凹陷中新统沉积特征及河道型岩性圈闭潜力

珠江口盆地恩平凹陷中浅层近年来相继有商业油气发现,虽目前仍然以构造圈闭为主,但古珠江三角洲相关岩性目标的评价亟待展开。基于高品质井、震资料,本次研究以恩平凹陷中新统珠江组上段—韩江组下段（T50—T35）为主要目的层,以三级层序界面和最大海泛面为界,建立了恩平凹陷T50—T35间的四级层序格架。在高精度层序地层格架的约束下,进一步采用地震沉积学手段揭示了恩平凹陷以分流河道为主的沉积特征,并建立了不同海平面背景下的河道沉积模式：海侵早期和高位末期河道规模较大,延伸距离较远,平面上常连片发育;海侵晚期和高位早期的河道规模适中,平面上孤立性较强,且前缘常被波浪改造。研究发现,不同类型的河道砂体与特定的构造背景结合可发育“河道切割型”岩性圈闭,并且最大海泛面上下更适合于相关圈闭的发育。据此,研究锁定了恩平A油田西侧斜坡带、E油田东侧斜坡带和G油田西侧披覆构造带等3个岩性圈闭有利区及2个有利勘探目标,为盆地岩性油气藏勘探提供了新思路。     

阳江-一统东断裂的新生代活动：从珠江口盆地西部构造特征与演化过程分析得到的启示

阳江-一统东断裂是珠江口盆地西部一条重要的NW向区域大断裂,是盆地东西分块的重要分界线。南海北部陆缘在新生代经历了大陆裂谷-裂离-海底扩张-热沉降的过程,阳江-一统东断裂在新生代的活动是这一复杂过程的一部分。对分处断裂两侧的从陆架延伸至洋陆边界的两条NNW向多道地震剖面进行了地质解释,研究了珠江口西部的构造和沉积特征。利用2D-Move软件及构造回剥法建立了平衡剖面模型,计算了断层活动速率,结合构造位置、构造演化史、标志构造和应力分析推断了阳江-一统东断裂在新生代的活动史。结果表明,阳江-一统东断裂可以中部坳陷带为界分为两段,从65Ma到32Ma,断裂整体表现为左旋活动,继承了断裂在中生代时期的先存左旋走滑,其中,在此时期断裂南段主要表现为伸展活动,伴随着轻微的左旋走滑,这种伸展活动控制了云开低凸起的形成和演化;从32Ma到23.8Ma,断裂北段的左旋走滑活动持续,而南段逐渐转为轻微的右旋走滑或左旋活动停止。在23.8Ma之后,断裂南段的右旋走滑活动持续,北段的左旋走滑逐渐停止,或转为轻微的右旋走滑。阳江-一统东断裂的这种走滑旋向的转变可能与在珠江口盆地南部洋陆过渡带区域的岩浆底侵作用有关。根据对盆地构造活动强度和裂谷格架的分析,认为阳江-一统东断裂的新生代活动在珠江口盆地裂谷伸展过程中起到了应力调节的作用。     

珠江口盆地番禺4洼古近系文昌组构造-沉积耦合关系

番禺04地区位于珠江口盆地番禺4洼缓坡带,番禺4洼在新近系发现多个油田,为“小而肥”的富生烃洼陷,但是古近系勘探尚未获得突破。结合录井、测井、三维地震资料,对研究区构造特征及演化过程、物源体系以及沉积充填特征进行系统研究。结果表明：研究区文昌期受NW向F1断裂活动控制,经历强烈断陷期、断陷萎缩期的构造演化过程;物源主要来自北部西江中低凸起,母岩类型为花岗岩,碎屑物质搬运距离中等,成分成熟度较高;研究区NW向断裂在早期NWW-NW应力方向控制下先活化,近EW向断裂在晚期NW-NNW向应力控制下后活化。NW向主要断裂在文昌组沉积早期活动性强,文昌组下段发育断控型扇三角洲沉积体系,文昌组沉积晚期基本不活动,文昌组上段发育坡控型辫状河三角洲沉积体系,具备发育优质储层的条件;基于原型盆地恢复认为,研究区发育“早期断控、晚期坡控”的构造-沉积响应模式,文昌组上、下段表现出明显的差异沉积充填特征,存在由断控型扇三角洲向坡控型辫状河三角洲转变的特征。相对而言,文昌组上段辫状河三角洲前缘相带砂体具“旁生侧储、近源成藏”特征,且埋藏更浅,砂岩粒度和分选磨圆更优,勘探前景优于文昌组下段扇三角洲前缘砂体。     

Applying seismic geomorphology to delineate switched sequence stratigraphic architecture in lacustrine rift basins: An example from the Pearl River Mouth Basin,northern South China Sea

Switched sequence stratigraphic architectural units were developed in the Eocene Wenchang Formation stratigraphic section of the Pearl River Mouth Basin (PRMB), northern South China Sea. Utilizing a high-quality 3D seismic data set, well logs and restored paleogeomorphology, the architecture and genesis of switched sequence stratigraphic units have been systematically investigated. The Wenchang Formation, a second-order sequence, can be subdivided into seven third-order sequences (from base to top: SQ1, SQ2, SQ3, SQ4, SQ5, SQ6, and SQ7). The sequence stratigraphic architecture of the Wenchang Formation is characterized by continuous lateral stacking patterns from sequences SQ1 to SQ7. Sequences SQ1–SQ4 mainly developed in the HZ26 sag, whereas sequences SQ5–SQ7 mainly developed in the XJ24 sag. The depositional centres of the Wenchang Formation appear to have migrated from the HZ26 sag to the XJ24 sag-along the northwest direction from sequences SQ1 to SQ7. Multiple tectonic activation episodes or alternating tectonic subsidence of the HZ26 and XJ24 sags resulted in the distinctive geomorphological features that effected the development of the switched sequence stratigraphic architecture in the study area. The switched sequence stratigraphic architecture presented in this study may provide new insights into a better understanding of sequence stratigraphic stacking patterns in continental lacustrine rift basins.     

Hydrocarbon generation and expulsion characteristics of Eocene source rocks in the Huilu area,northern Pearl River Mouth basin,South China Sea: Implications for tight oil potential

In recent years, new oil reservoirs have been discovered in the Eocene tight sandstone of the Huilu area, northern part of the Pearl River Mouth basin, South China Sea, indicating good prospects for tight oil exploration in the area. Exploration has shown that the Huilu area contains two main sets of source rocks: the Eocene Wenchang (E₂w) and Enping (E₂e) formations. To satisfy the requirements for further exploration in the Huilu area, particularly for tight oil in Eocene sand reservoirs, it is necessary to re-examine and analyze the hydrocarbon generation and expulsion characteristics. Based on mass balance, this study investigated the hydrocarbon generation and expulsion characteristics as well as the tight oil resource potential using geological and geochemical data and a modified conceptual model for generation and expulsion. The results show that the threshold and peak expulsion of the E₂w source rocks are at 0.6% vitrinite reflectance and 0.9% vitrinite reflectance, respectively. There were five hydrocarbon expulsion centers, located in the western, eastern, and northern Huizhou Sag and the southern and northern Lufeng Sag. The hydrocarbon yields attributed to E₂w source rocks are 2.4 × 10¹¹ tons and 1.6 × 10¹¹ tons, respectively, with an expulsion efficiency of 65%. The E₂e source rock threshold and peak expulsion are at 0.65% vitrinite reflectance and 0.93% vitrinite reflectance, respectively, with hydrocarbon expulsion centers located in the centers of the Huizhou and Lufeng sags. The yields attributed to E₂e source rocks are 1.1 × 10¹¹ tons and 0.2 × 10¹¹ tons, respectively, with an expulsion efficiency of 20%. Using an accumulation coefficient of 7%–13%, the Eocene tight reservoirs could contain approximately 1.3 × 10¹⁰ tons to 2.3 × 10¹⁰ tons, with an average of 1.8 × 10¹⁰ tons, of in-place tight oil resources (highest recoverable coefficient can reach 17–18%), indicating that there is significant tight oil potential in the Eocene strata of the Huilu area.     

珠江口盆地碳酸盐岩下构造深度校正探讨

地震资料显示, 高速层的存在会对下部地层产生上拉现象, 影响下部地层成像的准确性, 甚至产生构造假象, 给油气勘探带来预测难点。文章尝试从理论模型出发, 通过研究产生上拉的影响因素, 建立上拉系数量版法, 定量分析上拉幅度, 进而还原下部地层构造。研究表明: 上拉幅度受控于高速体速度、厚度和围岩速度, 交会量版说明上拉系数与高速体速度基本呈线性关系。在此基础上建立相应地质模型, 并进行实例解剖, 表明了此种方法对局部构造深度预测是有效的。     

珠江口盆地西江主洼泥-流体底辟及其发育条件

珠江口盆地西江主洼存在垂向的反射成像浑浊区域,这种垂向模糊区的地质成因多与盆地底辟活动相关。对西江主洼33西洼古近系地震资料中垂向模糊区的地震剖面特征形态及其地震波阻抗特征进行研究,并结合研究区盆地古近纪发育演化的特点认为,该模糊区拥有深、浅部反射不同的二元结构,可能是一处泥-流体底辟构造。西江主洼的古近系文昌组深湖相分布广泛,可以作为泥-流体底辟的泥源物质存在;33西洼钻井恩平组底部恩四段地层存在高压异常,恩平组顶部地层广泛发育的泥岩,可作为封存箱盖层,西江主洼具备形成封存箱的超压条件。而珠海期的岩浆侵入破坏了封存条件,诱发了盆地的泥-流体底辟活动,在33西洼古近系地层形成了深埋型-弱刺穿的锥状泥-流体底辟。     

珠江口盆地陆架坡折带海底滑坡及其影响因素

为了解海底滑坡在陆架坡折演化过程中所起的作用并分析影响海底滑坡发育的因素,以最新采集的二维和三维地震资料为基础,综合运用了地貌分析和地震解释技术,通过对滑坡的地貌形态特征及地震响应特征进行详细刻画,在珠江口盆地陆架坡折带新近纪地层中识别出多处海底滑坡,明确了其分布范围并建立了滑坡发育的地质模式。分析认为,珠江口盆地相对海平面变化和流体活动的综合作用是导致研究区海底不稳定的主要因素。海底滑坡发源于海底峡谷的朔源侵蚀,向上陆坡扩展并终止于陆架坡折带。     

珠江口盆地白云凹陷恩平组泥岩元素地球化学特征及环境指示意义

泥岩的元素特征对沉积环境变化有较高的灵敏度,能够较好地保存原始沉积记录。为了明确白云凹陷恩平组烃源岩发育环境,选取凹陷内5口钻井泥岩样品进行元素测试。利用元素地球化学方法,系统分析白云凹陷各洼陷恩平期古水深、古氧相、古气候、古盐度和埋藏效率等古环境指标,结果表明：白云西洼处于水深较深、气候偏冷潮湿、还原性弱的淡水环境,埋藏效率相对最低;白云东洼处于水深较浅、气候湿热、亚还原半咸水环境,埋藏效率高;白云主洼处于水深相对最深、暖湿气候、亚还原—还原的淡水环境,埋藏效率相对中等;白云南洼处于水深总体较浅、暖湿气候、亚还原环境,咸水—半咸水—淡水均有分布,埋藏效率总体趋好。环境恢复结果显示白云主洼、白云东洼和白云南洼恩平期烃源岩的形成和保存条件较好,白云西洼相对较差。     

Tracing of deeply-buried source rock: A case study of the WC9-2 petroleum pool in the Pearl River Mouth Basin, South China Sea

The identification of a deeply-buried petroleum-source rock, owing to the difficulty in sample collection, has become a difficult task for establishing its relationship with discovered petroleum pools and evaluating its exploration potential in a petroleum-bearing basin. This paper proposes an approach to trace a deeply-buried source rock. The essential points include: determination of the petroleum-charging time of a reservoir, reconstruction of the petroleum generation history of its possible source rocks, establishment of the spatial connection between the source rocks and the reservoir over its geological history, identification of its effective source rock and the petroleum system from source to trap, and evaluation of petroleum potential from the deeply-buried source rock. A case study of the W9-2 petroleum pool in the Wenchang A sag of the Pearl River Mouth Basin, South China Sea was conducted using this approach. The W9-2 reservoir produces condensate oil and gas, sourced from deeply-buried source rocks. The reservoir consists of a few sets of sandstone in the Zhuhai Formation, and the possible source rocks include an early Oligocene Enping Formation mudstone and a late Eocene Wenchang Formation mudstone, with a current burial depth from 5000 to 9000 m. The fluid inclusion data from the reservoir rock indicate the oil and the gas charged the reservoir about 18–3.5 Ma and after 4.5 Ma, respectively. The kinetic modeling results show that the main stages of oil generation of the Wenchang mudstone and the Enping mudstone occurred during 28–20 Ma and 20–12 Ma, respectively, and that the δ¹³C₁ value of the gas generated from the Enping mudstone has a better match with that of the reservoir gas than the gas from the Wenchang mudstone. Results from a 2D basin modeling further indicate that the petroleum from the Enping mudstone migrated upward along the well-developed syn-sedimentary faults in the central area of the sag into the reservoir, but that the petroleum from the Wenchang mudstone migrated laterally first toward the marginal faults of the sag and then migrated upward along the faults into shallow strata. The present results suggest that the trap structure in the central area of the sag is a favorable place for the accumulation of the Enping mudstone-derived petroleum, and that the Wenchang mudstone-derived petroleum would have a contribution to the structures along the deep faults as well as in the uplifted area around the sag.