Jianghan Basin, Qianjiang Sag Southeast Accumulation Model

The elements of petroleum system within the southeastern part of the Qianjiang Depression of the Jianghan basin have been systematically analyzed in this study using theories and technologies of petroleum system, pool-forming dynamics, hydrocarbon migration and reservoir prediction. The hydrocarbon accumulation conditions and control factors of the Lower Xingouzui Formation have been studied based on data available. The evolution pattern and prediction of reservoir and further potential exploration areas for oil and gas have been discussed and proposed. The major research progresses, new findings and suggestions are as follows:1. The characteristics and distributions of pool-forming elements including source rocks, reservoirs, seals, and migration pathways in the study area were analyzed. The results could concluded that the effective source rocks are mainly distributed in the areas of Zongkou and Panchang syncline. The significant reservoirs were considered to be consistent with the second and third oil groups in the Lower Xingouzui Formation of Tertiary. Two sets of seals, that is, the mudstone interval and Dagao interval of the Lower Xingouzui Formation were found, and the pathways of hydrocarbon migration were associated with sandstones, faults and fractures as conduits.2. On the basis of the previous research, the many aspects of understanding hydrocarbon accumulation regularity in the Lower Xingouzui Formation of Tertiary have been increased through this study. They are (1) the oilfield distribution is controlled by the main source rocks, and the oil layers are also controlled by the source rocks; (2) the richest hydrocarbon regions are located at the successive developed paleo-convex where the sandstones are well developed; (3) in the reservoirs in the first and third groups of the Lower Xingouzui Formation, the faults and their accompanying fissures are vertical conduits for hydrocarbon migration; (4) the trap types in the study area are primarily controlled by the sandstone bodies; (5) the structural reservoirs are developed in the underwater channels, sheet sandstones, and sand bars in deltaic front, lithological reservoirs mainly consist of sparse beach sands and sand bars or are located at the bays between distributing channels; (6) the structural and lithological complex reservoirs are developed in the areas where the sandstone thickness varies greatly.3. The studies indicate that the vertical hydrocarbon expulsion pattern; the fault-caused vertical migration and the lateral migration in the petroleum systems could be affected by the distribution of sedimentary facies, the distance from traps to source rocks and thereservoir evolution patterns of the Lower Xingouzui Formation, and that the characteristics of structure and reservoir should be important factors for the processes and patterns of petroleum migration in the studied area.4. According to the geological elements and functions of pool-forming and their models in combination with actual exploration, the favorable petroleum prospect areas and reservoir types have been recently pointed out, and two seismic reflection anomalies on the profile have been identified applying the high-resolution seismic data for reservoir prediction in the area of Jianxin.5. Through the research work of target description, the Zong 3 Well has be drilled in the Jianxin region, which is proposed to be a prospect area by this study, and further exploration plan for the area has been suggested.In summary, the results in my thesis, which is closely involved with the progress of exploration practice, have been providing important instructions for further petroleum exploration in the southeastern part of the Qianjiang Depression.