Structural Characteristics,Sedimentary Evolution And Hydrocarbon Accumulation Law Of Huoshanling Formation And Yingcheng Formation In Chaganhua-Dalhan Area

The Chaganhua-Dalhan area is located in the east of Changling fault depression.Several exploration Wells in this area have obtained high hydrocarbon gas flow(CH4content is more than 80%)in the volcanic rocks of Yingcheng Formation,revealing rich oil and gas resources and types of oil and gas reservoirs in the fault depression,which has great exploration potential.The preliminary exploration results show that volcanic rocks are still the main exploration subjects in the study area.With the further exploration of Yingcheng formation,it is more and more difficult to explore volcanic rocks.At present,unclear understanding of sedimentary filling evolution and reservoir-forming laws in Chaganhua-Dalhan area restricts the exploration in this area.In view of the existing problems,we should strengthen the research on structural evolution,sedimentary filling and reservoir-forming conditions,summarize the law of oil and gas enrichment and main controlling factors of reservoir formation,so as to provide basis for exploration deployment in the exploration area,and strive to achieve a new breakthrough in oil and gas exploration in Changling fault depression.Guided by the theories of structural geology,sedimentology and petroleum geology,and by the application of fine structural interpretation techniques of seismic data,growth fault analysis techniques,single well sedimentary facies analysis techniques and planar sedimentary facies analysis techniques,this paper has carried out structural and sedimentary characteristics analysis and oil and gas accumulation law research.The main research achievements are as follows:(1)Based on the study of fault growth index,the activity of various fault zones in Chaganhua-Dalhan area was analyzed.Combined with fault control,the tectonic units in the study area were re-recognized by controlling the stratigraphic distribution,the influence on volcanic rocks,the formation of convex belts and the tectonic pattern.(2)The development and distribution rule of Huoshanling Formation-Yingcheng Formation in the study area is analyzed.According to the drilling disclosure and seismic profile analysis,the south and north Chaganhua sub-depressions have dual filling characteristics,and the drilling in the south and north sub-depressions both reveal volcanic rocks and clastic rocks.From the seismic profile,it can be seen that volcanic rocks and clastic rocks overlap each other in space and there is a great difference between the north and the south.(3)The characteristics of volcanic facies and sedimentary facies in ChaganhuaDalhan area are clarified.There are four types of volcanic facies in this area: volcanic channel facies,eruption facies,overflow facies and volcanic sedimentary facies.Based on the understanding of tectonic evolution and sedimentary background,the modern theory of sedimentology is applied to determine that this area belongs to fan delta facies and lacustrine sedimentary system,and the sedimentary evolution characteristics of the study area are defined through the characteristics of single well facies and profile facies.(4)By analyzing the accumulation conditions of Chaganhua-Dalhan area,it is considered that Huoshiling Formation,Shahezi Formation and Yingcheng Formation in ChaganhuaDalhan area are self-generated and self-storage assemblages,belonging to deep hydrocarbon accumulation assemblage system.At the same time,hydrocarbon source,tectonic setting,trap availability and reservoir are the main factors controlling the accumulation and enrichment of natural gas.