东海陆架盆地是中国近海面积最大的含油气盆地，其中丽水凹陷勘探潜力巨大，具备形成大中型油气田的条件。由于丽水凹陷整体地质条件比较复杂，勘探程度较低，目前，勘探过程还面临诸如层序地层格架不统一、层序控制下的沉积相类型不确定、沉积体系内幕和空间发育规律不清楚等一系列的关键性地质问题。因此，本次研究基于区域地质、测录井、岩心、地震数据和薄片鉴定、ICP-AES元素鉴定、粘土矿物X-衍射、全岩矿物X-衍射、稀土元素鉴定、古生物鉴定、遗迹化石鉴定等分析实验，利用井-震联合对比、频谱分析、小波变换、相对海平面变化分析、地层切片、神经网络聚类及岩心描述刻画等沉积相综合表征技术，开展了丽水凹陷古新统层序地层控制下的沉积相及其发育规律研究，推动了丽水凹陷基本地质认识的统一，为下一步勘探工作中有利区的选取提供地质支持。

通过各级地震、测钻井层序界面的识别，辅以层序地层旋回和相对海平面变化分析，依据不同的层序地层模式，确定了丽水凹陷古新统地层划分方案，将古新统地层分为5个三级层序，即月桂峰组、灵峰组下段、灵峰组上段、明月峰组下段和明月峰组上段，进一步识别出13个四级层序，其中月桂峰组和明月峰组上段二分为水进体系域和水退体系域，灵峰组下段、灵峰组上段和明月峰组下段均三分为低位体系域、海侵体系域和高位体系域，建立了全区统一的层序地层格架。

在层序地层研究的基础上，结合现代沉积学考察和调研，开展了沉积特征和沉积相分析。丽水凹陷主要有西北、西南和东部三大物源体系，岩屑砂岩和长石岩屑砂岩最为发育，不同物源体系和不同层位砂岩类型有所区别，砂岩中石英、长石和岩屑平均含量分别为45.9%、13.8%、40.3%，成分中石英含量中等，岩屑含量较高，成分成熟度平均0.87。砂岩结构特征显示分选性以较差和中等为主，磨圆度以次圆-次棱角状为主，颗粒支撑以点-线和线接触为主，风化蚀变程度以中-深为主，主要粒径区间0.125~0.5mm，砂岩成分成熟度和结构成熟度均为中等。提出了以相对海平面变化和典型沉积构造为核心，古生物及地化指标为辅的沉积环境综合判别流程及方法，丽水凹陷古新统地层沉积时期月桂峰组以湖相沉积环境为主，主要为滨浅湖-半深湖，随着区域相对海平面上升，灵峰组和明月峰组地层沉积时期发生海侵，为海相沉积环境，主要为滨浅海-半深海，明月峰组上段地层沉积时期区域相对海平面下降，发生海退，凹陷整体为湖相沉积环境，主要为滨浅湖。基于二维和三维地震资料，开展了丽水凹陷古新统层序地层格架内地震属性优选与提取，进行沉积砂体分布特征的预测，优选和提取了不同四级层序内的均方根振幅属性进行砂体分布预测：平面上西次凹中部及北部地区砂体分布呈现条带状、斑状及不规则线性分布的特征，砂体走向基本呈北东-南西向分布，结合相对海平面变化特征，推测沉积砂体受改造的可能性较大，纵向空间中砂体整体表现为明月峰组最发育，月桂峰组次之，灵峰组最差的总体特征。识别出多种沉积相标志，主要包括神经网络聚类划分8类地震相：中强振幅-中频-较连续的平行亚平行反射，中弱振幅-中低频-较连续的平行亚平行反射，中弱振幅-中低频-中低连续反射，中弱振幅-中低频-低连续至杂乱反射，中强振幅-中低频-较连续的斜交前积反射，中强振幅-中频-较连续斜交前积反射，中弱振幅-中低频-较连续斜交前积反射，中强振幅-中低频-断续透镜状反射，分别反映小型河控三角洲、浪控三角洲和扇三角洲沉积特征；8种岩石相：层状含砾砂岩相（Gt），细粒至粗粒块状层理砂岩相（Sm），细粒至粗粒交错层理砂岩相（St），细粒至中粒板状层理砂岩相（Sp），极细粒至细粒沙纹层理砂岩相（Sr），极细至细粒平行层理砂岩相（Sh），水平层理粉砂岩和泥岩相（Fl）和块状层理泥岩相（Fm），划分出12种典型岩石相序列；21种典型测井相，其中3种前缘分流河道、2种前缘沙坝、1种沙席和1种河道间的典型测井相，指示扇三角洲前缘沉积，4种沙坝、2种沙席和1种沙坝间的典型测井相指示浪控三角洲沙坝-沙席沉积，4种分流河道、1种沙坝、1种沙席和1种分流间湾的典型测井相指示河控三角洲前缘沉积；4种遗迹相：石针迹遗迹相、二叶迹遗迹相、动藻迹遗迹相及石针迹-二叶迹遗迹相；刻画了单井沉积层序，识别出不同沉积体系的典型沉积层序，划分沉积相。

         通过层序地层模式、物源、岩石学特征、沉积环境、砂体和地震相等各类相标志的分析，认为丽水凹陷古新统发育西南物源的扇三角洲、西北物源的浪控三角洲（Ⅵ型）和东部物源的河控三角洲（Ⅰ型）三大沉积体系。其中扇三角洲以前缘沉积为主，月桂峰组和灵峰组最为发育，主要分布于丽水西次凹；浪控三角洲以前缘改造后的沙坝-沙席沉积为主，各层段均有发育，正常河控三角洲以前缘和前三角洲沉积为主，月桂峰组和明月峰组最为发育，主要分布于东次凹。不同沉积体系的有利相带分布为丽水凹陷古新统地层油气藏的形成提供了良好的储集砂体，是有利区带筛选的基础。

The East China Sea Shelf Basin is the largest offshore oil-gas bearing basin in China, in which Lishui sag has great exploration potential and the conditions to form large and medium oil-gas field. Due to the complex geological conditions and low degree of exploration in Lishui sag, the exploration process is faced with a series of key problems, such as the disunity of sequence stratigraphic framework, the uncertainty of sedimentary facies type under the control of sequence, the uncertainty of the internal and spatial distribution rules of sedimentary system, etc. Then, based on the regional geological data, logging data, core, seismic data and section identification, ICP-AES element identification, clay minerals X-diffraction, rock minerals X-diffraction, rare earth elements identification, paleontological identification, trace fossils identification and other analysis and test experiments, this study uses comprehensive characterization technology of sedimentary facies such as well seismic joint correlation, spectrum analysis, wavelet transform, relative sea level change analysis, stratal slicing, neural network clustering and core description technology to carry out the sedimentary system analysis under the control of Paleocene sequence stratigraphy in Lishui sag, so as to promote the basic geological understanding of Lishui sag unified, to provide geological support for the selection of favorable areas in the next exploration work.

Based on the different sequence stratigraphic models to identify the seismic and logging sequence boundaries at different levels, coupled with the analysis of sequence stratigraphic cycles and relative sea level changes, the Paleocene stratigraphic division scheme of Lishui sag is determined. The Paleocene strata are divided into five third-order sequences: The Yueguifeng formation, the lower of Lingfeng formation, the upper of Lingfeng formation, the lower of Mingyuefeng formation and the upper of Mingyuefeng formation, and 13 fourth-order sequences are further identified, the Yueguifeng formation and the upper of Mingyuefeng formation are divided into transgressive system tract and regressive system tract, the lower of Lingfeng formation, the upper of Lingfeng formation and the lower of Mingyuefeng formation are divided into lowstand system tract, transgressive system tract and highstand system tract.

Based on the study of sequence stratigraphic, combined with the investigation and research of modern sedimentology, the sedimentary characteristics and facies analysis are carried out. In Lishui sag, there are three major provenance systems in the Northwest, Southwest and East. The sandstone type is mainly lithic sandstone and feldspathic lithic sandstone. The sandstone types in different provenance systems and different sequences are different. The average content of quartz, feldspar and lithic debris in sandstone is 45.9%, 13.8% and 40.3%, respectively, the quartz content in the components is medium, and the lithic content is higher, the average maturity of components was 0.87. The textural characteristics of sandstone show that the sorting is mainly poor and medium, the roundness is mainly sub-circular and sub-angular, the particle support is mainly point-line and line contact, the weathering and alteration degree is mainly medium-deep, the main particle size area is 0.125-0.5mm, and the component maturity and textural maturity of sandstone are medium. This paper puts forward the comprehensive criteria and methods of sedimentary environment with the core of typical sedimentary structure and relative sea level change, supplemented by paleontology and geochemical indicators. The Yueguifeng formation in the Paleocene of Lishui sag is dominated by lacustrine sedimentary environment, mainly including shore-shallow and semi deep lacustrine environments. With the rise of regional relative sea level, transgression occurred in the sedimentary period of Lingfeng and Mingyuefeng formations, which are marine sedimentary environments, mainly shore-shallow and semi deep marine environments. During the sedimentary period of the upper part of Mingyuefeng formation, the relative sea level of the area decreased and regressed, the whole sag is a lacustrine sedimentary environment, mainly a shore-shallow lacustrine environment. Based on 2D and 3D seismic data, the Paleocene seismic attribute optimization and extraction of Lishui sag are carried out to predict the distribution characteristics of sedimentary sand bodies. The RMS amplitude attributes in different fourth-order sequences are optimized and extracted for sand body distribution prediction: the distribution of sand bodies in the central and northern part of the west sub sag in the plane presents the characteristics of strip, spot and irregular linear distribution, and the trend of sand bodies basically presents the distribution of the Northwest-Southeast, combined with the characteristics of relative sea level change, it is speculated that the sedimentary sand bodies are more likely to be transformed, as a whole, the sand body of Mingyuefeng Formation is the most developed, followed by the Yueguifeng formation and Lingfeng formation. A variety of sedimentary facies markers have been identified, including 8 types of seismic facies classified by neural network clustering: medium-strong amplitude, medium frequency, relatively continuous, parallel-subparallel reflection; medium-weak amplitude, medium-low frequency, relatively continuous, parallel-subparallel reflection; medium-weak amplitude, medium-low frequency, medium-low continuous reflection; medium-weak amplitude, medium-low frequency, low continuous to chaotic reflection; medium-strong amplitude, medium-low frequency, relatively continuous, oblique progradation reflection; medium-strong amplitude, medium frequency, relatively continuous, oblique progradation reflection. The results show that the sedimentary characteristics of small fluvial-controlled delta, wave-controlled delta and fan delta are reflected respectively. 8 lithofacies are identified: stratified gravely sandstone(Gt), fine- to very coarse-grained massive sandstone (Sm), fine to coarse-grained trough cross-stratification sandstone(St), fine to medium-grained planar cross-stratification sandstone(Sp), ripple cross-stratification sandstone(Sr), very fine to fine-grained sandstone with flat bedding (Sh), parallel laminated siltstone and mudstone (Fl), and massive mudstone (Fm) are divided into 12 typical lithofacies sequences. 21 kinds of typical logging facies, including 3 kinds of front distributary channels, 2 kinds of front sand bars, 1 kind of sand sheet and 1 kind of inter-channel typical logging facies, indicating fan delta front deposits, 4 kinds of sand bars, 2 kinds of sand sheets and 1 kind of between inter-bar typical logging facies, indicating wave-controlled delta sand bar-sheet deposits, 4 kinds of distributary channels, 1 kind of sand bar, 1 kind of sand sheet and 1 kind of distributary bay typical logging facies, indicating fluvial-controlled delta front deposit. There are four ichnofacies: Skolithos ichnofacies, Cruziaana ichnofacies, Zoophycos ichnofacies, Skolithos-Cruziaana ichnofacies. The sedimentary sequence of single well is also described, the typical sedimentary sequences of different sedimentary systems are identified, and the sedimentary facies are divided.

         Based on the analysis of sequence stratigraphic model, provenance, petrological characteristics, sedimentary environment, sand body distribution, seismic facies and various facies marks, it is considered that there are three depositional systems in Paleocene of Lishui sag: fan delta of southwest provenance, wave-controlled delta of northwest provenance (VI type) and fluvial-controlled delta of east provenance (I type). Among them, fan delta mainly developed front deposit, the Yueguifeng formation and Lingfeng formation are the most developed, which are mainly distributed in the West sub sag of Lishui sag; wave-controlled delta mainly developed sand bar-sheet deposit after front transformation, which is developed in all sequences, normal fluvial-controlled delta mainly developed front and fordelta deposit, the Yueguifeng formation and Mingyuefeng formation are the most developed, which are mainly distributed in the East sub sag. The favorable facies belt in different depositional systems provides a good reservoir sand body for the formation of Paleocene oil-gas reservoir in Lishui sag, which is the basis of the favorable areas selection in the next exploration work.