Major Controlling Factors Of The Neogene Hydrocarbon Charging In The Chengdao Area

This thesis comprehensively uses geological,seismic and logging data to systematically study the differences in the distribution of hydrocarbons in the Neogene and its main controlling factors in the Chengdao Area.By analyzing the distribution characteristics of Neogene oil and gas under the control of various elements of accumulation,the influence of different hydrocarbon accumulation elements on the differential enrichment of Neogene oil is discussed,and the main controlling factors of Neogene hydrocarbon differential charging at different scales are clarified.Along the Chengbei Fault,the main enrichment horizons of the oil and gas from the northwest to the southeast of the work area gradually become deeper;the fault-lithology and lithology-fault oil and gas reservoirs related to faults are mainly developed,and the Neogene oil and gas show typical heavy oil characteristics.There are obvious differences in the water characteristics of different structural belts.The main controlling factors of the differential charging of oil and gas between sand groups are analyzed from the aspects of cut-off,reservoir and cover characteristics and their mutual relations.The faults of the oil source are further divided into three types: penetration type,insertion type,and bridging type.The Neogene oil and gas in the study area is mainly distributed around the penetrating oil source fault.The faults of the oil source fault and the intensity of the fault during the accumulation period jointly control the Neogene.The degree of oil and gas accumulation;the sealing ability of Ngs1~3 regional caps determine the oil-bearing properties of the Nm Formation,while the internal sealing ability of the upper part of the pavilion controls the oiliness of the internal sand groups.Based on the role of sand body connectivity in sand migration in Neogene migration and accumulation,the types of reservoircaprock assemblage in the study area are divided into four categories,of which type I is most favorable to Neogene hydrocarbon enrichment,and type IV is most unfavorable to recent generations.Department of oil and gas enrichment,work area mainly develops type II reservoircaprock assemblage,which is more favorable to the enrichment of Neogene hydrocarbons.It can be seen that the differential filling between sand groups is mainly controlled by factors such as oil source fault development characteristics,seal layer,and reservoir-caprock assemblage.The sealing capability of cap rock determines the major oil and gas-enriched sand groups,and the development features of source faults,reservoir-caprock assemblage type controls the degree of hydrocarbon enrichment.From the aspects of reservoir lithology,thickness and direct cover,the main controlling factors for the differential filling of oil and gas between sand bodies are systematically studied.The Neogene oil and gas are mainly concentrated in the fine sandstone and siltstone reservoirs.The larger the size of the reservoir rock in the main oil-bearing strata,the higher the proportion of high-grade oil and gas displays,and the more favorable it is for hydrocarbon charging.The thickness of the reservoir also has a certain control effect on hydrocarbon charging.Its essence is caused by differences in physical properties: under the control of faults of the same oil source,the smaller the thickness of the reservoir sand body on the same side of the fault,the worse its physical properties tend to be.When the thickness of the reservoir is less than 1.5m,it is not conducive to hydrocarbon charging;while the thicker sand body has a wide distribution range,it has a higher requirement for the overlying direct capping layer and is more likely to cause oil and gas to escape,so when the reservoir thickness is greater than 7.5 m,the oil level in sand is generally low.In addition,the ability of the sand body to cover the direct capping layer determines the degree of crude oil enrichment in the upper and lower sand bodies.When the direct thickness of the pure mudstone layer is greater than the critical thickness,the oil in the underlying sand body can be effectively sealed.