丽水凹陷位于东海盆地台北拗陷西南部，是东海盆地中重要的油气聚集区带。随着常规油气产量衰减和不断增长的油气资源的需求，非常规油气藏以及海上油气藏的勘探成为了研究的热点。但是非常规油气藏埋深较大需要深钻井的支持，海上钻探的成本高昂，在较低勘探程度的条件下完成油气成藏机理的认知成为了亟待解决的问题。由于丽水凹陷油气地质条件比较复杂，并且目前勘探程度仍属于较低阶段，油气勘探工作一度遇到瓶颈。油气藏经历构造活动的改造和破坏，会在很大程度上影响油气的最终聚集，同时也制约了丽水凹陷油气成藏研究的深入进展和勘探区带的优化选择。本文对于丽水凹陷重点层段重新取样做了大量的分析化验工作，并建立了多维度的盆地模拟模型进行含油气系统分析。

根据烃源岩综合评价显示，月桂峰组烃源岩的有机质丰度高，生烃潜力高，成熟度高，主要属于中等－好烃源岩，其烃源岩厚度较大，是丽水凹陷的主力烃源岩，其次为灵峰组下段烃源岩。明月峰组和灵峰组上段烃源岩的有机质丰度和生烃潜力较低，主要属于差烃源岩，少量可以达到中等烃源岩。

通过黄金管生烃动力学模拟试验建立的生烃动力学模型得到，丽水凹陷月桂峰组烃源岩活化能生油区间主要分布于220kJ/mol左右，生气区间主要分布于220~250kJ/mol。油组分在低温段生成，油转化率达到80%时气组分大量生成，总转化率和气组分转化率相似，Ⅲ型干酪根产物以气组分为主。

通过对生烃演化剖面的分析得到丽水凹陷烃源岩的生油气门限深度大约在1750~2500m之间。深度未达到2500m时，烃源岩生成和排出的油气主要充填了泥岩内部的孔隙，作为残留烃存在；而深度超过2500m后，是大量油气从烃源岩层位排出的阶段；深度达到3300m深度时，排烃强度达到最高。

月桂峰组烃源岩的生烃量明显大于灵峰组上下段烃源岩，月桂峰组烃源岩的主要生烃期为58~32Ma，其中快速生烃期为58~50Ma。灵峰组烃源岩的主要生烃期为56~32Ma，其中快速生烃期为56~50Ma。在第四纪时，由于地温上升且灵峰组烃源岩转化率仍在较低水平，因此生烃量有少许上升。灵峰上段储层中的第一次油气充注历史始于56Ma，持续到32Ma的剥蚀事件，第二个充注期是从剥蚀事件结束后的23Ma开始，一直持续至今。

丽水凹陷圈闭数量众多且种类丰富，主要分布在古新统的明月峰组和灵峰组上段，且基本都在始新世末之前形成。凹陷内发育的烃源岩生烃时间都开始的比较早，具有早生早排的特点。古近系地层中的两套生储盖组合的排烃高峰与圈闭形成的时间也较为匹配，油气通过断层输导垂向运移到凹陷中部及东侧陡坡带成藏，西部斜坡带的油气主要通过断层、不整合、砂体运移，赋存在断陷期形成的古新统构造圈闭内。

Lishui Sag is located in the southwest of Taibei depression in the East China Sea basin, which is an important petroleum accumulation zone in the East China Sea Shelf Basin. With the decline of conventional oil and gas production and the increasing demand of hydrocarbon resources, the exploration of unconventional and offshore petroleum reservoirs has become a research hotspot. The unconventional reservoirs need the support of deep drilling however the high cost of offshore drilling makes it difficult. Due to the complex geological conditions of hydrocarbon in Lishui sag, the current petroleum exploration level is still in a low stage and once encountered a bottleneck. After the destruction and reconstruction of reservoirs affected by structural activities, the final accumulation zones of hydrocarbon are unclear. At the same time, it also restricts the research progress of hydrocarbon accumulation rules in Lishui Sag and the optimal selection of exploration zones. In this paper, a lot of analysis and test work has been done for resampling of key strata in Lishui Sag. A multi-dimensional basin simulation model has been established for petroleum system analysis.

According to the comprehensive evaluation of the source rock, the source rock of Yueguifeng Formation has high organic matter abundance, high hydrocarbon generation potential and high maturity, which is mainly medium to good source rock with large thickness. It is the main source rock of Lishui Sag, followed by the Lower of Lingfeng Formation. The organic matter abundance and hydrocarbon generating potential of source rocks in the Mingyuefeng Formation and Upper Lingfeng Formation are relatively low, mainly belong to poor source rocks. There is small amount of which can reach medium source rocks.

According to the hydrocarbon generation dynamic model established by the gold tube hydrocarbon generation dynamic simulation test, the source rocks of Yueguifeng Formation in Lishui Sag are mainly distributed around 220kJ/mol, and the gas generation range is mainly distributed in the range of 220kJ/mol to 250kJ/mol. The oil component is formed in the low temperature condition. When the oil conversion ratio reaches 80%, the gas component is generated in large quantity, the total conversion ratio is similar to the gas component conversion ratio. The type III kerogen product is mainly composed of gas component.

Based on the analysis of the hydrocarbon generation and evolution section, it is found out that the depth of hydrocarbon generation threshold is about 1750-2500m. When the depth is less than 2500m, the hydrocarbon generated and expelled from the source rock mainly fills the pores inside the mudstone and exists as residual hydrocarbon. The main hydrocarbon expulsion depth is over 2500m. The hydrocarbon expelling intensity reach the peak at the depth of 3300m.

The hydrocarbon generation of Yueguifeng Formation is larger than that of the Upper and Lower Lingfeng Formation. The main hydrocarbon generation period of Yueguifeng Formation is from 58Ma to 32Ma, and the rapid hydrocarbon generation period is from 58Ma to 50Ma. The main hydrocarbon generation period of the source rocks of Lingfeng Formation is from 56Ma to 32Ma, in which the fast hydrocarbon generation period is from 56Ma to 50Ma.

 In the Quaternary, due to the rise of formation temperature and the relatively low transformation ratio of Lingfeng Formation, the hydrocarbon generating quantity still increased a little. The first hydrocarbon filling period in the Upper Lingfeng reservoir started from 56 Ma and lasted to 32 Ma. The second filling period started from 23 Ma after the end of the erosion event and has lasted till now.

There are many kinds of traps in Lishui Sag, which are mainly distributed in the Mingyuefeng Formation and Upper Lingfeng formation of Paleocene and formed before the end of Eocene. The hydrocarbon generation time of the source rocks is relatively early, with the characteristics of early generation and early expulsion. The peak of hydrocarbon expulsion of the two sets of source reservoir cap assemblages in the Paleogene strata is also relatively matched with the time of trap formation. Oil and gas are vertically transported to the steep slope zone in the middle and east of the sag through fault plane, and the hydrocarbon in the western slope zone are mainly transported through faults, unconformities and sand bodies, and are stored in the Paleocene structural trap formed in the fault depression period.