Seismic Sedimentary Characteristics And Reservoir Forming Conditions Of Enping Formation In Baiyun 18-5 Block, Zhujiangkou Basin

Deepwater oil and gas exploration is one of the hotspots of oil and gas exploration in the world today.The deep water area of the northern slope of the South China Sea has great potential for oil and gas resources and exploration prospects.The Baiyun sag is a secondary structural unit located in the central area of the Pearl River Mouth Basin.The main body is in the deep water area with huge potential for oil and gas resources.Fan delta is an important place for oil and gas accumulation.Oil and gas enrichment is found in many places in the southern slope of the Baiyun sag and the periphery of the Yunkai low bulge.Due to the large depth of the Enping Formation in the Baiyun Depression,the fault activity in the southern steep slope zone is strong,and the characteristics of hydrocarbon accumulation in the fan delta have not been thoroughly studied.Based on two-dimensional and three-dimensional seismic data,the paper studies the sedimentary facies of the Enping Formation in the Baiyun Depression,focusing on the identification of fan deltas and promoting oil and gas exploration in the tectonic layers of the depression.Based on the actual situation of domestic and foreign research,progress and regional geology,based on the research status and progress of the study area and regional geology,the drilling data of the study area,sufficient 2D and 3D seismic data and predecessors The research results,by identifying the interface between the logging stratification and the seismic landmark layer,summarizing the structural combination style of the Enping Formation;identifying the seismic facies types and their distribution characteristics of the target layer of the Enping Formation by seismic facies analysis,combined with the seismic attribute characteristics,and the earthquake The phase and sedimentary facies are transformed to clarify the sedimentary facies types and their distribution characteristics of the Enping Formation.In this period,the main body of the depression is mainly shallow sea and shallow sea,and the fan delta is deposited in the steep slope on the south side of the depression.The target body of the middle section of the Enping Formation in the steep slope of the southern margin of the Baiyun sag is a fan delta,which has a leaf-like distribution with a fan area of 356 km~2.Based on the vertical superposition relationship and seismic attribute characteristics of the fan-delta-like leaf-shaped leaf body,the fan delta is divided into three stages,and the sediments in different stages show the characteristics of S-to-NE and N-direction progressive accumulation.Based on the analysis of delta geometry,the analysis of paleo-geomorphology and the identification of faulted valleys,it is clarified that the fan delta is provided by the southern uplift belt,the negative geomorphology formed by the faulted valley is transported to the basin,and the sedimentary source is controlled by multi-level faults.Canal-sink system.The characteristics of the integrated fan delta plane distribution,the sedimentary period division and the provenance system analysis,combined with the structural features of the middle section of the Enping Formation in Baiyun Depression,it is clear that the formation and distribution of the fan delta is mainly controlled by the syngenetic fault in the depression.The hydrocarbon accumulation conditions of the Fanping Formation in the Enping Formation of Baiyun Depression were systematically analyzed and the accumulation model was established.There are two main source rocks that can provide oil source for the target fan delta reservoir.They are the lacustrine source rocks of the Eocene Wenchang Formation and the shallow marine source rocks of the Lower Enping Formation.The source rocks contain more organic matter.The thickness is large.By analyzing the logging data of the steep slope zone in the southern part of the Baiyun sag,the fan delta is developed during the Enping Formation,and the reservoir properties are good and there are oil and gas accumulations.The shallow marine mudstone on the top of the Enping Formation has strong capping ability;The faults develop,and most of them are oil source faults.The oil and gas are mainly transported by short-distance vertical migration.According to the relationship between fault structure and sedimentary structure,10 traps are identified in the fan-developed area,mostly faults controlled by normal faults.The block is closed and the nose is closed,and the structural-lithologic composite trap is less,with a total area of 85.6km~2.Based on the comprehensive geological conditions of oil and gas accumulation,the fan-delta accumulation of the Enping Formation in the Baiyun Depression has the characteristics of"distribution along the fault along the plane and upward uplifting in the vertical direction".