古珠江三角洲是珠江口盆地油气勘探的重要目标,但对其总体沉积面貌的揭示仍未充分,在一定程度上限制了对区内有利砂体和潜在岩性圈闭的锁定.本次研究综合利用重矿物、岩心、钻井和区域三维地震数据,采用地震沉积学综合分析手段精确复现了早?中中新世古珠江三角洲的宏观沉积格局和相带展布.重矿物分析结果显示,古珠江分流河道体系向近端侧主要发源于西侧、东侧两个主河道分支,进而确定了古珠江三角洲"双支主控"的宏观基本格局.此外,经过对这两个分支河道体系重矿物组合特征对比,发现其分别与现代西江、东/北江有一定相似性,这可能表明中新世古珠江干流的流路与现今具有较高对比性.同时,针对分流河道和外缘条带砂的精细地震地貌分析显示出中新世古珠江三角洲可能受到河流?波浪?潮汐混合动力过程的影响,并且持续的西南向古水流对整体相带展布也具有明显的控制作用.

珠江口盆地珠一坳陷惠州26洼为典型的断陷盆地,是已证实的富生烃洼陷.以往对优质烃源岩的研究主要集中在其盆地内部,而对湖盆边缘次洼的烃源岩特征及形成机制鲜有报道.为弥补以往研究的空白,选择惠州26洼东北次洼作为研究区,根据最新的地震、地化和元素分析等资料,对该次洼的烃源岩地化特征和形成机制进行详细研究.结果表明,该次洼文四段发育优质烃源岩,有机质丰度高,含量均值为4.59％,可达"好—很好"烃源岩标准,有机质类型为Ⅰ—Ⅱ1型,以生油为主.文四段沉积时期,惠州26洼东北次洼强烈断陷,形成"洼缘深盆",且陆源碎屑物质输入量少,为烃源岩发育提供有利的沉积环境,同期火山活动提供了丰富的无机营养物质,形成咸水环境,引起浮游生物勃发,促进有机质的规模形成和保存.综合分析认为,惠州26洼东北次洼文四段优质烃源岩的发现,将优质烃源岩分布范围扩大至湖盆边缘,为该洼陷未来勘探发现奠定生烃基础,对其他地区断陷盆地边缘洼陷评价和勘探潜力分析具有重要的借鉴意义.

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.

运用放射性元素寻找油气是一种非常规油气勘探手段.近年来,在珠江口盆地珠一坳陷富烃凹陷周边古近系钻遇高自然伽马(GR)砂岩,其GR值(100～300 API)甚至大于同区泥岩的GR值(100～200 API).为了弄清该特殊现象背后的地质意义,对珠江口盆地珠一坳陷古近系高自然伽马砂岩开展了铀(U)、钍(Th)、钾(K)等3种元素含量与GR值的相关趋势线分析,从井震特征、岩性特征及矿物成分特征等入手分析了砂岩GR值增高的主要原因及成因机制,探讨了放射性元素聚集的条件、运移通道、驱动力以及油气意义.结果表明:西江、惠州地区由U含量增高导致砂岩GR值偏高,恩平、番禺地区由K,Th含量增高导致砂岩GR值偏高;砂岩GR值增高有两大成因机制,一是地下流体带来的放射性元素离子U4+在氧化-还原面处富集后导致地层GR值偏高,这种特殊现象说明在具有连通基底大断裂旁的圈闭中,U4+的富集指示了曾经油气的存在,证实了研究区油气运移通道的有效性,对于油气藏的预测有着非常重要的指导性意义,二是地表流体带来的含放射性元素的矿物大量沉积后导致地层GR值偏高,含放射性元素矿物性质不稳定,可指示近源供给的存在,对于判断物源及沉积环境有着非常重要的意义.该研究成果为预测研究区油气成藏有利区带提供了依据.

珠一坳陷深层古近系两套优质生烃层系内发育的储层具有近源成藏的优势,但其非均质性强、低孔渗的特点制约了油气勘探,研究与此直接相关的"源-汇"系统,对于寻找富烃优储耦合的有利区意义重大.以构造运动和盆山地貌为基础,结合断陷湖盆以半地堑为基本单元的结构特点,划分了盆地级、半地堑级和区带级的三级"源-汇"系统.盆地级分为外源、内源型两类,可用来宏观分析优质烃源岩分布;半地堑级分为陡坡、缓坡和长轴型3类,对于定性评价储层优劣具有较大意义;区带级分为迁移型、转换型、稳定型3类,为有利区目标评价和井点选择提供参考.研究认为迁移型和转换型"源-汇"系统可形成良好的生储盖配置,是最为有利的油气富集区,应作为古近系重点勘探对象.

西江主洼是珠江口盆地一个低勘探程度洼陷,油气差异聚集特征明显,但其机理不清.本文在断陷盆地油气成藏理论指导下,利用研究区地质、地球物理和地球化学等资料,开展了烃源岩、断盖组合、储集体系和运聚模式等方面的研究.结果 表明,裂陷期沉降、沉积中心有序迁移,造成主力烃源岩自东向西由文四段迁移至文三段、文一十二段,控制东、西部油气差异分布.恩平组区域性泥岩发育且晚期断裂缺乏,导致油气纵向上更易聚集于下构造层;区域泥岩减薄尖灭或晚期断裂切开盖层的区域,上构造层有一定油气分布.“源-汇”类型从宏观上控制储层优劣,影响下构造层油气富集程度;“仓储”运移是控制上构造层油气规模聚集的主要模式.下构造层古近系应作为重点部署方向,东部围绕文四段、西部围绕文三段、文一+二段烃源岩构成的含油气系统展开;上构造层勘探需关注珠海组,在隆起周边寻找具备“仓储”运移模式的有利区带.

南海东部海域经过30多年的油气勘探,在浅水区非烃源层系取得了岩性油藏的勘探突破.目前已发现的岩性油藏相对集中在惠州凹陷南部珠江组,通过对其岩性油藏的分布特征、类型及主控因素开展详细解剖,划分出上倾尖灭型、背斜-上倾尖灭复合型、断层-上倾尖灭复合型和条带型4类岩性油藏.其有利成藏条件主要受4种因素控制:①河流、波浪和潮汐等多水动力交互控制着储层的平面分布特征,不同水动力控制了不同的储层和岩性圈闭类型;②海平面的多期升降控制了储-盖组合,在主要成藏期具有6套有利成藏组合;③东沙运动控制了岩性圈闭的有效性和运移通道,调整了砂体的尖灭、翘倾状态,有利于岩性圈闭形成和成藏;④"烃源-断层-构造脊"的立体耦合影响油气的高效聚集.南海东部浅水区可划分出3类共6个岩性油藏勘探潜力带.

Multiphase rifting with tectonic quiescence intervals is one of the most distinguishing features during the evolution of rift basins and rifted margins, which always produce oceanward rift migration. However, this law seems to be challenged in the proximal domain of the northern South China Sea (SCS) rifted margin. Based on highquality 2D/3D seismic reflection data and borehole data from the Zhu 1 Depression located in the northern SCS, we examine the temporal and spatial variations of rifting. The regional unconformity, cyclicity of faulting, and rotation in extension direction indicate that the Zhu 1 Depression experienced continuous two-phase rifting with four stages but without distinct tectonic quiescence intervals. In Stage 1 of Syn-rift 1, rifts were distributed across the whole depression. They began to migrate towards the continent in stage 2 of Syn-rift 1, which continued until stage 1 of Syn-rift 2, and then migrated to the east. Rifting was also accompanied by a clockwise rotation of the strikes of fault systems, which were similar to N065 degrees E and similar to N080 degrees E in stage 1 and stage 2 of Syn-rift 1, respectively, and then rotated to similar to S085 degrees E during Syn-rift 2. We suggest that the interactions between the preexisting basement fabrics and the regional stress fields rotating clockwise can account for this rotation and the eastward rift migration. The rift migration towards the continent is supposed to be caused by the emplacement of the high-velocity lower crust (HVLC) underneath the Dongsha Uplift, which may initiate in the Eocene. The distinctive multidirectional, multiphase, and multi-mechanical rift migration reflects the uniqueness of the SCS rifted margin. This study helps us understand the complicated rifting process that interacts with pre-existing fabrics, regional stress field, and the emplacement of high-velocity lower crust.

珠一坳陷在中始新世文昌裂陷期幕内存在显著构造转变,该构造事件对烃源岩发育、储层形成及油气运聚等成藏的基础条件有重要影响.基于三维地震、钻井、测井、录井等资料研究表明,在构造转变制约下,早、晚文昌期生烃中心及物源体系出现明显迁移,使得高丰度暗色泥岩和大型块状砂岩在纵、横向上错层叠置发育;二者在时空上多期次叠加、耦合,控制了下构造层优势汇聚和上构造层油气再分配;二级构造带上丰富的圈闭类型为油气成群成带分布提供良好的存储场所.构造转变导致生储运聚等成藏条件发生变化,在珠一坳陷形成烃源迁移型、物源迁移型和断裂转换型3类控藏模式.

During the Miocene, when the Zhujiang Formation was deposited, the eastern part of the Pearl River Mouth Basin, northern South China Sea, underwent intense mixed siliciclastic and carbonate sedimentation, particularly on the platform of the marginal ramp of the Dongsha Rise, northeastern margin of the South China Sea. Cores and well logs from industrial boreholes were collected and systematically investigated to reveal the sedimentary-petrographic characteristics of the mixed deposits and their formative processes. Four lithotypes were differentiated in the deposits, that is, (1) sandstone, (2) dolomitic sandstone and calcitic sandstone, (3) sandy dolomite and sandy limestone, and (4) dolomite, bioclastic limestone, and micrite limestone, which were formed by three major types of mixing processes: punctuated, facies, and in situ mixing processes. The porosity and permeability of the mixed deposits indicated that the siliciclastic component of the mixed deposits that experienced punctuated mixing formed the most high-quality hydrocarbon reservoirs. Exploration revealed that the lithologic reserves in the study area were mainly developed in mixed sedimentation areas. Our results suggest that the mixed sedimentation area, particularly with pure sandstone sedimentation or bioclastic sandstone, that underwent compaction or structural fracture activities, may be the next preference for lithologic exploration.

摘要: 珠一坳陷在中始新世文昌裂陷期幕内存在显著构造转变，该构造事件对烃源岩发育、储层形成及油气运聚等成藏的基础条件有重要影响.基于三维地震、钻井、测井、录井等资料研究表明，在构造转变制约下，早、晚文昌期生烃中心及物源体系出现明显迁移，使得高丰度暗色泥岩和大型块状砂岩在纵、横向上错层叠置发育；二者在时空上多期次叠加、耦合，控制了下构造层优势汇聚和上构造层油气再分配；二级构造带上丰富的圈闭类型为油气成群成带分布提供良好的存储场所.构造转变导致生储运聚等成藏条件发生变化，在珠一坳陷形成烃源迁移型、物源迁移型和断裂转换型3类控藏模式. 关键词: 构造转变 / 富生烃洼陷 / 优质储层 / 油气成藏 / 珠一坳陷 / 油气地质

The Huizhou Movement refers to the Middle Eocene tectonic transition from the early to the late Wenchang Rifting stage（about 43 Ma ago） in the Pearl River Mouth Basin. Based on seismic reflection, drilling, logging and geological data, fault characteristic analysis, denudation thickness recovery, magmatism statistics, regional tectonic dynamics comparison and other methods are used to reveal the characteristics, properties and dynamic mechanism of the Huizhou Movement. The Huizhou Movement mainly shows the North-South transition of rifting and the migration along the faults, basement uplift, magmatic diapir and stratigraphic denudation. It is believed that the Huizhou Movement is a comprehensive reflection of plate interaction and lithospheric thinning process in the Pearl River Mouth Basin, which is closely related to the transition of lithosphere from initial rifting to rapid thinning, the India-Eurasia hard collision and the change of subduction direction of the Pacific plate. The Huizhou Movement has significant influence and control on the Paleogene hydrocarbon-generating sags and the development of hydrocarbon source rocks, sedimentary system and deep high-quality reservoir, hydrocarbon migration and accumulation in the Pearl River Mouth Basin.

由于前人对南海北部陆缘新生代早期形成的火山岩岩石类型、成因和地球动力学背景存在不同的认识,通过对珠江口盆地惠州凹陷钻井揭示的粗面质集块/角砾熔岩、粗面岩、流纹岩和粗面英安岩开展了相关锆石U-Pb年代学和全岩地球化学研究.结果表明研究区新生代火山岩形成年代介于57.53～59.15 Ma,靠近古新世(Paleocene)和始新世(Eocene)之间的界限,落入坦尼特阶(Thanetian).岩石具有较高的SiO2(64.60％～73.22％)、Al2O3(11.86％～16.57％)含量,低MgO(1.16％～1.80％),高Sr(305.20×10-6～465.50×10-6,平均值为371.15×10-6)含量,低Y(7.47×10-6～9.84×10-6)、Yb(0.90×10-6～1.43×10-6)含量及高Sr/Y比值(35.19～54.55),富集轻稀土(LREE)、亏损重稀土(HREE),富集大离子亲石元素(LILE)Ba、K等、亏损高场强元素(HFSE)Nb、Ta、Ti和P元素,具有轻微的Eu正异常,显示埃达克质岩石的地球化学特征,属于钙碱性-高钾钙碱性-钾玄岩系列,准铝质岩石(A/CNK=0.85～1.04).这些早古近纪埃达克质岩可能是由先期底侵的镁铁质下地壳在石榴石-角闪岩岩相条件下发生部分熔融作用的产物,认为南海北部陆缘新生代时期发生的拆沉作用在岩浆形成演化过程中可能起到了重要作用.

In this paper, we investigate the structure of the Cenozoic rift basin in the proximal domain of the northern South China Sea (SCS) margin, with an emphasis on the influence exerted by pre-existing basement faults on rift development. Results of our work indicate that the overall rift architecture of the proximal domain of the northern SCS margin is associated with extensional faults arranged in two main structural trends, WNW- to EW-trending and ENE-trending. Structural evidence presented in this paper suggests that extensional faults of the two main structural trends mainly reactivated two pre-existing basement fault systems mapped in previous works, a WNW- to EW-striking thrust fault system (PFS1) and an ENE-striking thrust fault system (PFS2). During the first rifting phase, both pre-existing fault systems were reactivated; however, strains and depocenters were mainly localized on the ENE-striking normal fault system that reactivated the PFS2. On the contrary, in the second rifting phase, extension was mainly accommodated by WNW- to EW-striking normal faults that reactivated the PFS1, while most of the earlier ENE-striking normal faults became inactive or less active. These different degrees of reactivation of the two pre-existing fault systems during the two rifting phases suggest a clockwise rotation of the regional extension direction from NNW-SSE in the Syn-rift stage 1 to N-S in the Syn-rift stage 2. This study implies that apart from Cenozoic tectonic processes, pre-existing structures have also played a key role during rifting evolution across the SCS margin.

在三级层序格架下分析了珠江口盆地番禺4洼文昌组烃源岩生物标志化合物纵向演化特征及影响因素,优选出T/C30藿烷、Ts/Tm及C304-甲基甾烷／C29甾烷等参数作为原油族群划分和油源对比的主要指标,厘清了该洼陷区已发现原油的来源和分布规律.研究认为,以高丰度C304-甲基甾烷、极低丰度双杜松烷T构型化合物和Ts与Tm相对含量均势为主要特征的第1类原油来自文四段半深湖—深湖相烃源岩,以高丰度C304-甲基甾烷、明显检出双杜松烷T构型化合物和Ts与Tm相对含量均势为主要特征的第2类原油来自文三段半深湖—深湖相烃源岩,以较高丰度C304-甲基甾烷和双杜松烷T构型化合物以及Ts较Tm显著优势为主要特征的第3类原油来自沉积环境相对偏氧化的文二段烃源岩.番禺4洼文昌组烃源岩中双杜松烷T构型化合物相对含量很可能受沉积时代和沉积环境的双重控制,上、下文昌组烃源岩中双杜松烷T构型化合物丰度变化可能与陆源区龙脑香科植物的逐步繁盛有关,较高丰度双杜松烷T构型化合物与高丰度C304-甲基甾烷的共存反映了在以低等水生生物来源有机质为主的宏观背景下具有一定丰度陆源树脂类有机质的输入.

源-汇系统研究是当今世界范围内地球科学领域颇为关注的重要课题.源-汇系统划分是源-汇系统定量化研究和精细解剖的基础,但是国内外关于源-汇系统级次划分的报道比较少见,更多是集中在源-汇系统源-渠-汇单元耦合、参数拟合、预测及其控制因素分析等研究.以分水岭、分水线和脊线分别作为划分一级、二级和三级源-汇系统级次划分的界线和依据,总结、归纳出三级源-汇系统级次划分方法、流程,并选取云南洱海现代湖盆源-汇和珠江口盆地珠一坳陷西江凹陷XJ23洼南部低凸起古代湖盆源-汇实例解剖,开展三级源-汇系统级次划分方法的应用分析.云南洱海"点苍山-洱海"现代源-汇系统可以划分为东、西侧两个一级源-汇系统,东侧一级源-汇系统划分为19个二级源-汇系统,15号二级源-汇系统进一步划分为A、B两个三级源-汇系统.珠江口盆地珠一坳陷西江凹陷XJ23洼南部低凸起古代源-汇系统可以划分为A、B、C三个一级源-汇系统,一级源-汇系统A划分为A1、A2、A3、A4四个二级源-汇系统,二级源-汇系统A3进一步划分为I、II两个三级源-汇系统.三级源-汇系统级次划分方法对源-汇系统定量化研究和精细解剖方面具一定的参考价值.

西江主洼位于珠江口盆地珠一坳陷的中西部,是珠江口盆地重要的富生烃凹陷之一.为了认识珠江口盆地西江主洼边界断层(Fxj33)属性特征,基于钻井约束的高精度三维地震资料,对Fxj33断层几何学和运动学进行了综合分析.研究揭示Fxj33边界断层为低角度生长正断层,倾角5°～36°,呈NEE走向,长度约55 km,最大水平位移达9.5 km左右.在多幕裂陷演化过程中,Fxj33断层沿走向上表现为分段差异活动特征,并与两排EW向高角度断裂共同控制着西江主洼各次级洼陷的发育演化.中生代基底中发育的叠瓦状构造、残留山和先存断面等一系列构造表明Fxj33边界断层为中生代先存逆冲构造体系在新生代反转形成,并且在断陷中晚期进一步被一系列EW向高角度断面切割改造,形成现今形态.期望研究结果对被动陆缘断陷盆地边界断层的形成和演化研究有指示意义.

珠江口盆地惠西南地区隆洼间发育一系列转换带型沟谷源-汇系统,勘探程度较低,一直以来主要依靠地震资料进行沉积相刻画.本文基于最新的高分辨率三维地震资料,以区域古地貌为基础,定量表征了惠州25、27转换带分水岭、分水线、汇水单元等沟谷体系的基本要素.作为沟通物源区与惠州26洼的重要输砂通道,转换带汇聚了物源汇水区的碎屑物质,并沿转换带沟谷再次搬运入湖,这一过程中碎屑物质经过强水动能改造,成熟度进一步提高.基于源-汇系统认识,对惠州27转换带地震相进行了分析,认为碎屑物经两级沟谷体系入湖,形成了文四段早期的进积型扇三角洲与文四段晚期的退积型辫状河三角洲,完善了该地区物源、搬运、沉积三要素之间的源-汇耦合关系,对深挖转换带型沟谷体系潜力具有参考价值,推动了惠西南地区惠州27转换带古近系的勘探进程.

为了明确白云凹陷北坡珠江组下段陆架边缘三角洲的形成演化阶段及其主要控制因素,采用地震沉积学、层序地层学的相关理论和方法,结合钻测井数据、地震反射结构特征和均方根振幅属性等资料,在前人研究的基础上对该陆架边缘三角洲的识别特征、演化模式和控制因素进行了重新认识和探讨分析.结果 表明:陆架边缘三角洲在顺物源方向具有高角度斜交型前积反射,缺乏顶积层的海岸平原相,其前端发育盆底扇沉积;垂向沉积序列以多期反旋回的前三角洲、席状砂、河口沙坝和水下分流河道的叠置为特征,发育陆坡区常见的生物扰动、泥质条带变形和滑塌、滑动现象;珠江组下段陆架边缘三角洲形成于强制海退体系域时期,并伴随着盆底扇的发育,而低位体系域时期主要发育斜坡扇和低位楔状体;构造活动促使白云凹陷北坡在珠江组下段时期形成稳定分布的陆架坡折带,珠江组下段时期古珠江携带的充沛物源和该时期强烈的海平面下降使碎屑沉积物能够进积至陆架边缘,甚至陆坡地区形成陆架边缘三角洲沉积.

利用地震沉积学、层序地层学的相关理论和方法,结合钻测井数据、地震反射结构特征、均方根振幅属性和滨线迁移轨迹特征等资料,对珠江口盆地白云凹陷北坡21 Ma强制海退体系域的识别特征、演化模式和油气意义进行了探讨,指出该体系域在平行物源方向具有高角度斜交型前积反射,其前端靠近盆地中心发育具丘状反射的盆底扇,滨线迁移轨迹呈向盆地方向逐级下降的趋势.结果表明:强制海退体系域在垂直物源方向发育"U"型的下切谷,内部为平行的地震反射充填结构;测井曲线为漏斗形和箱型的组合特征,表现为多个四级相对海平面变化控制的准层序组,且每个准层序组都具有向上水体变浅和顶部突然变深的特征;强制海退体系域之下为前期层序高位体系域的前三角洲或陆架泥岩,其上沉积了海侵体系域和高位体系域的半深海暗色泥岩,同时受陆架坡折带地层尖灭和断裂沟通深部油源的控制,可形成有利的生、储、盖组合,是寻找岩性油气藏的有利场所.