The hydrocarbon generation model and hydrocarbon potential are investigated in the Lishui Sag, based on gold-tube pyrolysis experiments of deeply buried type Ⅲ kerogen. From this, we discuss the classification of kerogen types of source rocks with mixed organic matter sources. The hydrocarbon generated from the source rocks of the Lingfeng Formation and Yueguifeng Formation is dominated by natural gases with little oil in the West subsag, and the hydrocarbon generation model of the Lingfeng Formation is similar to that of Yueguifeng Formation, but the gas potential of Lingfeng Formation is higher than that of Yueguifeng Formation. The hydrocarbon potential of the Yueguifeng Formation in the East subsag is much higher than the West subsag, and it has considerable oil potential. Macerals diversity of source rocks is responsible for the difference of hydrocarbon generation characteristics for type Ⅲ kerogen in the Lishui Sag. It is not rigorous to evaluate the hydrocarbon potential of kerogen only based on pyrolysis parameters. Application of kerogen type index (KTI) can improve the accuracy of the classification of kerogen types with mixed organic matter sources. According to the classical kerogen classification template, the selected samples belong to type III kerogen. In this article, the selected samples were further subdivided into type III and type II/III based on the KTI value. Type III kerogen (0.5 ≤ KTI < 1.5) mainly produces gas, and type II/III kerogen (1.5 ≤ KTI < 5) mainly produces gas, but its oil potential is higher than that of type III.

Okavango delta is a typical distributive fluvial system, which is composed of a series of sand island-river-swamp networks. River migration in the Okavango delta is analyzed by using satellite images from Google Earth and Alaska Satellite Facility (ASF). Four configuration characterization parameters are selected to depict and measure the meandering river. These four parameters are sinuosity index (S), curvature (C), the difference of along-current deflection angle (Δθ) and expansion coefficient (Km). In the fan, the channel migration is mainly asymmetric. According to geomorphic elements and associated features, Okavango Delta can be subdivided into three zones: axial zone, median zone and distal zone. Under the influence of slope, climate and vegetation, different migration modes are developed in different zones. As the river moves downstream, the sinuosity index of the river on the Okavango Delta decreases downstream. Based on the characteristics of different zones, the sedimentary facies model of a single source distributive fluvial system of a meandering river is proposed. The models of channel migration and sedimentary facies have wide application. This research will not only provide a basis for the prediction of future river channels but will also provide important theoretical guidance for the study of the sedimentary morphology of underground reservoirs.

Although a large number of meandering rivers have been studied by means of modern sedimentation, instrument detection, numerical simulation, flume experiment and field outcrop, and a lot of achievements have been made, there are not many fine anatomical examples of deep buried ancient rivers, which is a situation that still needs to be improved. The main difficulties in the research of deep, ancient meandering rivers are the acquisition of data and the incompleteness of structure, which are both difficulties and challenges. Under the guidance of the modern meandering river fan sedimentary model and migration law, we established the scheme of meandering river geomorphology and structure. In the process of river migration, a variety of single migration models (expansion, contraction, rotation, and translation) and composite migration models can be distinguished. By analyzing the distribution structure characteristics of channel configuration elements in different migration modes, the coupled model of the meandering channel plane and profile structure is established by systematically constructing plane and profile combined with a three-dimensional channel configuration model. Based on the data of the dense well, taking the Shan 11 sublayer in the Su-x block of the Sulige gas field as an example, the reservoir structure of the deep, ancient meandering channel is dissected. In order to reconstruct the evolution of the deep, ancient channel and make it more consistent with the real laws of river migration and evolution, the morphological migration law of the modern river is applied to the ancient sedimentation, and the migration configuration is dissected by combining with the plane-profile structure coupled model. It further reveals the heterogeneity, the vertical distribution and the superposition form of the channel sand, and enriches the theory of the reservoir configuration of underground fluvial facies, all of which are significant for oil and gas exploration and development.

为了探究不同热演化阶段的咸水湖相烃源岩排出油和滞留油生物标志化合物演化规律及其指示意义，选取了渤海湾盆地辽中北洼沙一段咸水湖相烃源岩样品开展了多路分段式热压生排烃模拟实验。结果表明：研究区咸水湖相烃源岩在Ro为0.56 %时已经有少量液态烃生成，具有早期生油的特点。随着热演化程度升高，高成熟阶段中轻烃占比明显增大。成熟度指标中的∑三环萜烷/17α-藿烷和C30莫烷/C30藿烷在滞留油成熟至高熟阶段，可作为判断成熟度的可靠参数，在排出油中变化较小；沉积环境与母质来源指标中的C26TT/C25TT、C35/(C31-C35)升藿烷、（nC21-+nC22+）/（nC28-+nC29+）与C27/C29规则甾烷在排出油中保持稳定，但在滞留油中变化较大。通过对比排出油与滞留油成熟度、沉积环境与母质来源参数发现：排出油与滞留油的演化规律存在一定的差异性。排出油中指示沉积环境和母质来源的生标参数可靠性较高而滞留油中指示成熟度的参数可靠性较高。

Although abundant unconventional oil resources have been discovered in conglomerate and sandstone reservoirs in rift basins, the mechanism of differential pore evolution in conglomerates and sandstone reservoirs within different secondary structural zones of rift basins is not yet clear. The pore structures of conglomerate and sandstone reservoirs in the distinct secondary structural zones in the Chezhen Sag were quantified in three dimensions using high-resolution microcomputed tomography (micro-CT). Thin section and scanning electron microscopy observations were used to investigate the differential evolution mechanisms of conglomerate and sandstone reservoirs. Micro-CT analysis of the pore structures of conglomerate and sandstone reservoirs revealed that sandstone reservoirs are superior to conglomerate reservoirs with regard to the pore number and pore connectivity and that sandstone reservoirs are more heterogeneous than conglomerate reservoirs. Triangles dominate the pore and pore throat geometries of sandstone and conglomerate reservoirs, while the sandstone reservoir pores are more regular than conglomerate reservoir pores. The depositional environment, mineral composition, and diagenetic intensity jointly control the quality of the reservoirs. Because of the lengthy transportation distance of their parent rocks, the compositional maturity and sorting behavior of sandstone reservoirs in depression and gentle slope zones are better than those of conglomerate reservoirs in steep slope zones, and thus sandstone reservoirs have a higher initial porosity than conglomerate reservoirs. The rapid compaction experienced by the conglomerate reservoirs in steep slope zones in their early stages creates a closed diagenetic environment, making it difficult to effectively improve reservoir porosity through dissolution. However, the widely developed microfractures in the reservoirs provide channels for fluid migration, promote the development of dissolution pores, and form a tight reservoir dominated by secondary pores. With weak compaction and an open diagenetic environment, the primary pores in sandstone reservoirs in the gentle slope zone are preserved in large quantities. Meanwhile, dissolution expands the secondary pores of the reservoir, resulting in a high-quality reservoir having both primary and secondary pores. In addition, an approach based on primary, secondary, and total porosity was proposed in the study to efficiently evaluate reservoir quality and identify reservoir evolution mechanisms.