Fine Structural Interpretation And Comprehensive Traps Evaluation In Dongying Formation Of Eastern Hongliu Area

The eastern Liulin area is located in slope belt between Gunan sag and Kendong uplift,and has multiple oil-bearing systems.Among them,only KD 55-X5 and KD X522 oil-bearing blocks of Dongying formation were explored in the study area,and the geological reserves accounted for only 4.5%of the entire Hongliu region.In this paper,the geological,seismic,logging and oil test data were used to synthetically study the stratigraphic development,reservoir/cap,fault system and accumulation controlling factors of Dongying formation,further,the exploration type and area of Dongying formation oil reservoirs are broadened.The stratigraphic division and stratum statistics of 27 wells were completed under the controlling of stratigraphic framework by using the reference plane and the combination method of the equal time and thickness principle to compare the target layer.Based on synthetic seismogram and Dongying velocity analysis,combined with coherent analysis and horizontal slice,fine structural interpretation of top/bottom and four sand sets(Ed₂?Ed₃?Ed₄?Ed₅)of Dongying formation in study area were explained.In conclusion,fault systems in the area are very developed,and they are en-echelon faults with the direction of NNW or NEE.Among them,the Kendong fault went through the whole Dongying formation,which is very important to accumulation of oil in Dongying formation.The activity and evolution of two groups of fault systems with the direction of NNE-NE and NEE-NWW in Eastern Hongliu area were systematically studied by growth index method.fault system During the period of before the early Es₄ to the Tertiary,the faults of NNE-NE experienced the uneven activities of strike-slip and extensional fault,strong and weak alternating.Finally,present fault structure pattern was formed during Dongying stage.In Tertiary accumulation stage,the NEE-NWW faults have great active intensity and long duration,which have a great influence on the structure and deposition of the Dongying formation in the region,and control the reservoir migration,enrichment and formation of traps.Taking typical main fault as an example,the relationship between fault distance,growth index and heterotaxy is studied,and the evolution law of fault activity was quantitatively represented.The typical tectonic and tectonic-lithologic oil reservoirs of Dongying formation were dissected,and the main controlling factors of accumulation were clarified.They respectively are:(1)Gunan sag and Zhuangdong sag provide abundant oil sources;(2)micro-structure controls the formation of a single oil reservoir;(3)large oil source faults are the channel of communication between the source beds and the Dongying formation;(5)good reservoir and seal assemblage is the key to accumulate;(6)meshwork-carpet type oil and gas pool-forming system is the main accumulation model of Dongying formation in this area.The study found that there were five favorable traps in Dongying formation.They respectively are KDX 552 trap,the GD27 lithologic trap,the KD56 Overlap stratigraphic trap,the GD 26 overlap stratigraphic Trap,the GD 26 lithologic trap.