Tracing secondary oil migration pathways is critical for understanding petroleum system evolution histories. Traditional tools (e.g., molecular indicators and numerical modeling) utilized for evaluating oil migration processes either lead to ambiguous interpretations or only provide qualitative estimates. We quantitatively constrain secondary oil migration processes under an absolute time frame by integrating oil-inclusion fluorescence and in situ calcite U-Pb dating on calcite veins and cements hosting primary oil inclusions. Fluorescence spectra of oil inclusions and U-Pb ages were obtained on samples from ultra-deep Ordovician reservoirs along two major faults in the Halahatang oilfield, Tarim Basin (northwestern China). Absolute U-Pb ages suggest two main oil charge events during 475–433 Ma and 294–262 Ma, respectively, and revealed a northward-decreasing trend for oil maturity during single charge events. Vertical migration of oil from in situ source rock through active (or reactivated) faults is believed to be the key process inducing the spatial maturity variation in charged oils and considered as the main mechanism of secondary migration, with brecciated fault zones and dilatant fractures along faults acting as major vertical oil-migration pathways. The successful application of this approach has wider implications for elucidating petroleum migration processes in tectonic complex basins worldwide.

基于琼东南盆地三维地震资料及钻井获取的岩性、电性、薄片及测年等分析测试数据，开展宝岛凹陷南部断阶带渐新统陵水组三段（简称陵三段）源-汇体系特征及源-汇耦合定量分析等研究。研究表明：①陵三段沉积期YL10剥蚀区发育东、西2大物源水系，在宝岛凹陷南部形成了2大优势输砂通道及2个三角洲朵叶体，整体具有西大东小的特征，可划分为初始期、昌盛期、间歇期和回春期4个演变阶段；②综合三角洲砂体发育期次、展布面积、碾平厚度及不同类型母岩区面积、成砂系数等参数进行源-汇耦合定量计算，结果显示研究区具备形成规模储集体的物质基础；③钻井揭示陵三段三角洲沉积以细砂岩为主，砂岩总厚度为109~138 m，最大单层厚度为15.5~30.0 m，砂地比为43.7%~73.0%，不同断阶间储层物性差异明显；④断阶带多期隆升背景下小物源区规模三角洲发育模式揭示幕式隆升提供充足的物源供给，物源水系及流域面积控制砂体的规模，多级活动断阶控制砂体的输送通道，局部断槽控制砂体的侧向推进方向。陵三段三角洲砂体与断块耦合形成多类型圈闭，成为凹陷南部重要的勘探突破口和新领域，有望为盆地内其他构造背景相似区域油气勘探及储层研究提供借鉴。

In this paper，37 fluid inclusion samples from 6 wells in the eastern area of Qiongdongnan Basin have been employed to systematically obtain information including the observation of fluorescence colors and the measurement of homogenization temperatures, and the results indicate that there are four phases of thermal fluid flow relative to hydrocarbon chargings in the area. Integrated the average homogenization temperatures with burial historical curves, this paper concluded that the charging orders respectively correspond to 20-18 Ma(Early Miocene), 10-6.5 Ma (Late Miocene), 5.5-2 Ma (Pliocene) and 2-0 Ma (Quaternary). In those periods, Pliocene and Quaternary are the primary stages of hydrocarbon charging. The first period fluid is mature thermogenic gas, the second one is low mature oil and gas, the third one is moderate and high mature gas and lease condensate, and the fourth one is maturehigh mature gas accompanying a little mature light oil. Furthermore, mantlesource carbon dioxide has charged in local area since Middle Miocene (14 Ma), which hindered hydrocarbon migration and accumulation in late-stage.

宝岛凹陷是琼东南盆地新生代构造活动最强烈的凹陷，2022年在宝岛21转换断阶带发现中国首个深水深层大型气田——宝岛21-1气田，证实了宝岛凹陷的天然气资源潜力。在宝岛21-1气田基本地质特征认识的基础上，系统分析气田烃源岩富集生烃机理、储层-圈闭形成机制、断裂体系运聚机理和天然气成藏期次及成藏模式，总结针对深水深层的地球物理与测试作业攻关创新技术。宝岛21-1构造发育"双源"有机质富集，地壳强烈薄化导致构造具高热流值，烃源岩热演化加速、生气强度大；隆起区物源沿转换斜坡注入凹陷，形成大型三角洲朵叶体控制的构造+岩性圈闭；大型构造脊利于天然气汇聚，主控断层差异活动与三角洲砂岩构成高效输导系统，具备形成大型气田的地质基础。宝岛21-1气田具有多期油气充注，证实转换断阶带发育"半封闭环境富集/高热加速生烃控源—转换斜坡控圈—长期活动断裂控运—晚期多期强充注—弱活动断裂控聚"的天然气成藏富集模式。建立深水陡陆坡崎岖海底区深层油气地球物理探测关键技术，实现了构造精细落实与含气性成功预测；创建深水深层复杂流体流动安全保障与产能释放关键技术，保障了地层真实产能释放。宝岛21-1大型气田的发现，证实强活动型被动陆缘盆地油气成藏富集模式，认为相对稳定的走向斜坡型转换带是大—中型气田富集的"黄金带"。研究认识为宝岛凹陷天然气勘探指明了方向，对琼东南盆地乃至南海北部及中—南部天然气勘探具有重要的借鉴与启示意义。

In Qiongdongnan Basin, Baodao sag is considered as the one where the strongest Cenozoic tectonic activity occurred. In 2022, China's first large deep-water and deep-layer gas field, i.e., Baodao 21-1 gas field, was discovered in Baodao 21 transition step-fault zone, thus verifying the potential of natural gas resources of Baodao sag. Based on the understanding of the basic geological characteristics of Baodao 21-1 gas field, the paper systematically analyzes the enrichment and hydrocarbon generation mechanism of source rocks, the reservoir-trap formation mechanism, the migration and accumulation mechanism of fault system, and the accumulation stages and accumulation models of natural gas of the gas field, and summarizes the groundbreaking and innovative geophysical and testing technologies for deep-water and deep-layer gas fields. Baodao 21-1 structure develops "double source" organic matter enrichment, and the intense crustal thinning leads to high heat flow in the structure, as well as accelerated thermal evolution and high gas generation intensity of source rocks; the provenance of the uplift is injected into the sag along the transition slope, forming a tectonic and lithologic trap controlled by large delta lobes; large-scale tectonic ridges are conducive to natural gas accumulation, and the differential activities of main faults and delta sandstones constitute an efficient transport system, which can provide a geological foundation for the formation of large-scale gas fields. Baodao 21-1 gas field has multi-stage oil and gas charging, proving that the transition step-fault zone develops a natural gas accumulation and enrichment mode of "enrichment in semi-enclosed environment/accelerating hydrocarbon generation at high temperature for source control, relay ramp for trap control, long-term active fault for controlling hydrocarbon migration, late multi-stage strong charging, and weak active fault for controlling accumulation". This study develops the key technologies for deep layer oil and gas geophysical exploration in the rugged seabed area of deepwater steep slope land, thus achieving the fine construction of structure and successful prediction of gas-bearing properties, and creates key technologies for safety control of flowing of deepwater and deep layer complex fluid and capacity release, thus guaranteeing the release of real production capacity of the formations. The discovery of the large gas field Baodao 21-1 has confirmed the oil and gas accumulation and enrichment mode of passive epicontinental basin with strong activity. It is believed that the relatively stable strike slope type transition zone is the "golden zone" for enrichment in medium- and large-scale gas fields. The relevant research and understanding point out the direction for natural gas exploration in Baodao sag, and have important reference and enlightenment significance for natural gas exploration in Qiongdongnan Basin, the northern and central-southern South China Sea.

利用新三维地震资料，相干切片等技术对琼东南盆地深水区宝南断阶带断裂进行了精细解释；结合区域构造特征，对宝南断阶带断裂形态、断裂活动性进行了分析，并探讨了断裂对天然气成藏的控制作用，分析了其地质意义。结果表明，宝南断阶带断裂平面上以NWW_SEE向为主，主要呈平行状或网状,剖面上共发育3组构造断裂，主要呈顺向断阶状样式；断裂主要为3期活动：①始新世—早渐新世、②晚渐新世早中期、③早中新世；宝南断阶带断裂控制了宝岛凹陷南部烃源岩的形成与演化，控制了陵水组、三亚组砂体空间展布和构造圈闭的形成，同时为主要的油气垂向运移通道。并结合油气生排烃史、圈闭形成史，认为断裂活动与油气成藏的匹配关系良好。在此研究的基础上，提出2个有利勘探层系。

The faults in the Baonan step-fault zone are described by using new high density 3D seismic data and coherence technique.A detailed study of fault morphology and fault activity in Baonan step-fault zone of deep-water area in Qiongdongnan Basin was carried out based on the regional structural characteristics.The controlling function of faults on natural gas accumulation is researched in this study.The results showed that the combination type of fault is parallel-aligned and grid-type which are mainly in NWW-SEE direction.Three groups of faults were recognized in the seismic sections which were forward step-fault types.There are mainly three periods of fault activity.Such as Eocene-Early Oligocene，early-mid of Late Oligocene，and Early Miocene.The faults in the step-fault zone affected the development and evolution of hydrocarbon source rocks in south Baodao Sag.The faults control the spatial distribution of sandstone and the development of structural traps in Sanya Formation and Lingshui Formation.The dense faults in the zone provide channel for hydrocarbon vertical migration.Additionally，the results showed that the fault active period matched well with hydrocarbon accumulation by the data of hydrocarbon generation and expulsion history and trap formation history.Through these researches，two favorable exploration strata are put forward in this paper.

琼东南盆地深水区是中国海上油气勘探的前沿阵地和油气资源接替的重要战略选区，而确定烃源岩分布特征是深水区低勘探领域石油地质研究的首要任务。在预测及确定中央坳陷带东部渐新统烃源岩厚度、成熟度和有机相等分布特征的基础上，通过计算烃源岩体积、生气量、生气强度等，完成了烃源岩的综合评价，最终实现了富生烃凹陷的优选。研究表明:①整体上，陵水组烃源岩厚度大于崖城组，其中崖二段和陵二段为烃源岩最为发育的层段，同时泥岩沉积中心表现出从西向东、从崖城组零星分布到陵水组统一连片的演化趋势;②烃源岩热演化呈现西早东晚、现今成熟度呈现西高东低的趋势;③渐新统烃源岩质量整体较好，其中煤层为优质烃源岩，泥岩为中等—好烃源岩;崖城组主要有机相为浅海相和滨海相，而陵水组主要有机相为内、外浅海相;④宝岛凹陷、长昌凹陷和松南凹陷均达到富生气凹陷级别，但前者综合评价为最好级别，后两者则分别为较好和一般。

琼东南盆地受深部构造、周边各大板块运动及南海扩张所形成的区域应力场的控制，发育了新构造运动。新构造运动对琼东南盆地烃源演化、储层发育、圈闭形成具有重要的控制作用，同时新构造运动形成的晚期断裂，沟通了深部烃源层和深浅目的层，有利于古近系、新近系纵向叠置复式成藏。琼东南盆地东部和南部的陵南低凸起、松南低凸起、长昌凹中隆起带和宝岛北斜坡，古近系与新近系均发育良好储盖组合，晚期断裂发育，油气纵向运移有利，具有油气纵向叠置、横向连片复式成藏的可能，可以期待有良好的勘探前景，这些新构造运动发育地区是琼东南盆地下一步勘探的方向所在。

深水区是当前油气勘探的前缘领域之一，其储集体分布与成因是成藏研究的关键难题。琼东南盆地宝岛凹陷已被证实为富生烃凹陷，但凹陷内超深水区目前仍未取得商业油气勘探突破，主要原因在于中深部储层展布规律认识不清。以宝岛凹陷南部斜坡带为例，应用地震反射结构识别、地震相几何形态刻画、地震属性约束等地震沉积学预测方法，明确陵水组和三亚组海底扇平面展布。研究结果表明，宝岛凹陷斜坡带陵水组扇三角洲呈现平行斜交型前积反射特征，滑塌型海底扇呈透镜体反射特征，三亚组海底扇呈现亚平行席状反射特征。基于源—汇体系分析，明确宝岛凹陷斜坡带扇体沉积物源来自于西南侧松南低凸起及南部隆起，多支下切水道发育为沉积物搬运提供了有效运输通道。地震沉积学预测方法及源—渠—汇沉积过程分析理论的应用为宝岛凹陷深水区油气勘探及成藏条件分析奠定了地质基础。

基于石油的荧光性，通过常规荧光光谱方法，对油包裹体的荧光光谱进行定量化描述，利用其主峰波长（λ_max）、红绿熵（Q）及QF₅₃₅等属性参数，并根据λ_max与QF₅₃₅的相关关系特征，可以便捷而有效地开展油气充注期次的判识。齐家地区上白垩统青山口组高台子致密油储层中9块流体包裹体样品检测结果表明，高台子油层中发育发黄色、黄绿色、蓝绿色3种荧光颜色的油包裹体；高台子油层油包裹体λ_max与QF₅₃₅分布在3个区域，从黄色荧光区域→黄绿色荧光区域→蓝绿色荧光区域，QF₅₃₅值逐渐减小，反映了油包裹体中捕获原油的成熟度逐渐增高；并结合埋藏史、生烃史和包裹体均一温度研究，认为齐家地区高台子油层在地质历史时期共经历了3幕油气充注，早期原油充注发生在白垩纪嫩江晚期79—77Ma期间，对应于第1幕充注；晚期原油充注发生在晚白垩世明水期69—65Ma期间，对应于第2幕和第3幕充注。

Based on the fluorescence property of petroleum, the conventional fluorescence spectroscopy was adopted to quantitatively describe the fluorescence spectrum of oil inclusions. The hydrocarbon charging events can be identified conveniently and effectively based on its attribute parameters (e.g. main peak wave length (&lambda;_max), red-green entropy (<em>Q</em>) and <em>QF</em>₅₃₅) and the relationship between &lambda;_max and <em>QF</em>₅₃₅. 9 samples of fluid inclusions taken from Gaotaizi tight oil reservoir of Qingshankou Formation, Upper Cretaceous in Qijia area were tested. It is indicated that the oil inclusions of three fluorescent colors (i.e., yellow, yellow-green and blue-green) are developed in Gaotaizi oil reservoir. &lambda;_max and <em>QF</em>₅₃₅ of oil inclusions in Gaotaizi oil reservoir are distributed in three regions. The <em>QF</em>₅₃₅ decreases gradually from yellow fluorescence region to yellow-green fluorescence region and to blue-green fluorescence region, reflecting the gradual increase of the maturity of crude oil entrapped in oil inclusions. Then, combined with the studies on burial history, hydrocarbon generation history and homogeneous temperature of inclusions, it is concluded that Gaotaizi oil reservoir in Qijia area has experienced 3 hydrocarbon charging events in the period of geological history. The early charging of crude oil occurred in the late stage of Cretaceous Nenjiang (79-77 Ma), corresponding to the first event of charging, and the late charging occurred in the Mingshui period of Late Cretaceous (69-65 Ma), corresponding to the second and third events of charging.

对392个地温梯度数据和234个大地热流数据的统计结果显示:南海北部深水区地温梯度为2.94～5.22℃/hm,平均为3.91&plusmn;0.74℃/hm;大地热流值为24.2～121mW/m²,平均为77.5&plusmn;14.8mW/m²。南海北部地区现今地温场具&quot;热盆&quot;属性,且深水区比浅水区更&quot;热&quot;。大地热流总体变化趋势为:从陆架到陆坡(从北到南)逐渐增高,且增高趋势与地壳减薄趋势一致,同时,平面上存在显著的局部异常点。新生代岩石圈拉张减薄以及新构造运动引发的岩浆、断裂活动是南海北部深水区具&quot;热盆&quot;特征的根本原因,南北向岩石圈减薄程度控制了大地热流总体变化趋势,新构造运动引发的岩浆与断裂活动则是局部热流异常形成的根本原因。

运用流体包裹体、有机地球化学分析和压力模拟手段，综合研究了琼东南盆地东部Ⅱ号断裂带新生界多期热流体活动及天然气运聚特征。研究结果表明：①琼东南盆地东部Ⅱ号断裂带BX19-2构造天然气主要为烃气和CO₂，烃气为煤型气和油型气的混合气，但不同气层中天然气组分含量差异较大，浅部三亚组气层为相对高含量的烃气（体积分数为83.93%）和低含量的有机成因CO（2体积分数为7.11%）；较深部的陵水组气层为含量相对较低的烃气（体积分数为16.10%～76.63%）和含量相对较高的幔源CO（2体积分数为18.70%～81.56%）。②流体包裹体和岩石地球化学参数显示烃气运移与3期热流体活动相关，每期热流体的活动深度及引起的热异常程度均存在一定差异。3期含烃热流体活动的时间分别为中新世晚期（约8.8 Ma）、上新世（约4.5～4.1 Ma）和第四纪（约1.1～0.1 Ma）。③热流体是以断裂为主要通道发生垂向高效快速充注。来自宝岛凹陷深部的幔源CO₂在上新世晚期—第四纪（约2.2～0.5 Ma）发生充注，并驱替了陵水组储层的烃气。因此，宝岛凹陷Ⅱ号断裂带附近的圈闭可能具有钻遇高CO₂含量的风险。

Based on fluid inclusion analysis，organic geochemistry data，and pressure simulation，the multiphase thermal fluid activity and natural gas migration-accumulation in the No. 2 fault zone of the BX19-2 structure in eastern Qiongdongnan Basin were studied. The results show that：（1）The natural gas in the BX19-2 structure primarily consists of hydrocarbon gases and CO₂，with the hydrocarbon gases being a mix of coal-derived gas and oil-derived gas. However，there is a significant variation in the composition of natural gas across different gas zones. The shallow gas zones in the Sanya Formation exhibit a relatively high content of hydrocarbon gases（volume fraction of 83.93%）and a low content of organogenic CO₂（volume fraction of 7.11%）. In contrast， the deeper gas zones in the Lingshui Formation contain relatively lower concentrations of hydrocarbon gases （volume fraction ranging from 16.10% to 76.63%）and higher concentrations of mantle-derived CO₂（volume fraction ranging from 18.70% to 81.56%）.（2）Fluid inclusions and geochemical parameters of rocks indicated that the hydrothermal activity was related to hydrocarbon migration，with variations in the depth and extent of the induced thermal anomalies. There were three phases of hydrocarbon-bearing hydrothermal activities occurred during the late Miocene（approximately 8.8 Ma），Pliocene（approximately 4.5 to 4.1 Ma），and Quaternary （approximately 1.1 to 0.1 Ma），respectively.（3）The hydrothermal fluids primarily utilized faults as major conduits for vertical，efficient，and rapid charging. Mantle-derived CO₂ from the deep Baodao Sag was injected during the late Pliocene to Quaternary period（approximately 2.2 to 0.5 Ma），displacing the hydrocarbon gases accumulated in the Lingshui Formation. Therefore，traps near the No. 2 fault zone of the Baodao Sag may pose a risk of encountering gas zones with high CO₂ content.

近年来，南海北部琼东南盆地深水西区天然气勘探取得了重大突破，证实深水区具备良好的烃源和油气成藏条件。但由于地质条件的复杂性，琼东南盆地深水区烃源岩规模及生烃潜力、油气成藏机制及分布规律、下一步勘探突破领域依然不是很清楚。针对上述关键问题，本研究综合运用地球化学与地质分析方法，开展琼东南盆地深水区烃源条件与油气成藏机制研究，进而指出琼东南盆地深水区下一步有利的油气勘探突破领域。研究认为：琼东南盆地中央坳陷深水区发育始新统湖相、渐新统崖城组海陆过渡相及半封闭浅海相2套3种类型的烃源岩，其规模大、热演化程度高，生烃潜力巨大，为琼东南盆地深水区天然气勘探提供了坚实的物质基础。琼东南盆地深水区油气成藏条件优越，但深水西区与深水东区油气成藏机制存在一定差异。深水西区乐东_陵水凹陷中央峡谷周缘上中新统轴向水道、海底扇岩性圈闭带和陵水凹陷南部斜坡古近系/潜山圈闭带以及深水东区的宝岛凹陷宝南断阶带、长昌凹陷西部环A洼圈闭带为下一步油气勘探的重要突破领域。上述成果对于解决琼东南盆地深水区天然气勘探瓶颈问题、指明下一步勘探突破方向具有重要的科学和勘探实践意义。