| Jiangling sag is the main oil and gas accumulation and distribution area in Jianghan basin, Wancheng fault zone is the main oil and gas exploration zone in Jiangling sag, but the distribution of oil and gas has a great discontinuity and uncertainty on the fault zone. As a direct pathway between down plate of hydrocarbon source rocks and the upthrown reservoir, Wancheng fault sealing ability, especially the differences in different areas closed to to be further studied, which has important theoretical significance and important application value to make clear about the hydrocarbon accumulation and distribution.After years of oil and gas exploration and research work, predecessors have already established the tectonic framework and the important oil and gas formation in Jiangling sag, but previous work showed obvious characteristics of Jiangling depression, namely the study of Jiangling sag fracture system as a whole to work more, while the research on the internal difference of the secondary structural units in the depression is relatively few; For local specific sedimentary reservoir, structural characteristics and reservoir distribution law is more,but the main controlling factors of hydrocarbon accumulation in the analysis of fracture system, the role of fracture system in oil and gas accumulation research are almost none.The paper makes full use of the petroleum system, the oil and gas accumulation system and dynamics of reservoir, comprehensive geological data and geophysical data.Based on the analysis of the geological condition of the formation and evolution of the faults, the types of traps, the assemblage of reservoir and cap. Combined with the influence factors of fault sealing, using qualitative and quantitative method to study the sealing ability of Wancheng fault from south to north. Summarize the influence of different regional sealing differences on oil and gas accumulation, in order to construct the Jiangling sag Wancheng fault belt of oil and gas accumulation process, summed up the main control factors of reservoir, put forward the oil and gas enrichment region.Through the research, it is concluded the following points:(1) Jiangling sag has experienced six main tectonic evolution stages since the cretaceous:Cretaceous fault period、Shashi fault depression period、Xingou zui depression period、Jingsha fault depression period、Qianjiang Group fault sag period、Jinghe zhen uplift and rosion stage and Neogene weak compression. In the process of sag tectonic evolution, Wancheng fault zone started its activities from the end of the cretaceous, in Jingsha formation sedimentary period to end.(2) Jiangling sag fault plane distribution can be summarized as parallel composition, pinnate combination and radial combination three plane combination styles.Ling Bei northern margin of the northern fault zone, fracture combination of Fuxing chang anticline belong to radial composite style, feather combinations are widely distributed in the middle of Wancheng fault. Wancheng fault can be divided into three sections according to the fault in profile performance:the northern part shows that reverse fault on the top and normal fault on the bottom. In Cretaceous,the fault throw is relativity large,and the layer above Xingouzui formation occurred stongly reverse compression.In the middle,the activity of fault become weak and even stop in the period of Qianjiang formation,and the whole fault show a extensional normal fault.In the southern part,the top of fault reversed,and the fault throw become smaller,while the fault totally show that reverse fault on the top and normal fault on the bottom.(3) Wancheng fault seal depends on cross-section shape of the fault, the relationship between the main fault strike and the formation of stress, the section on both sides of the formation of connecting relationship and the sealing property of the fault rocks, etc. As can be seen from the characteristics of mudstone smear analysis of Xingouzui formation,the SGR value of Wancheng fault is generally greater than 60%, indicating good sealing closure of Wancheng fault overall. Wancheng fault in the process of long-term activity, due to the different activity intensity of North and south, resulting in lateral variations of fault plane sealing, Wancheng fault closure in space has a strong heterogeneity.(4) The oil source correlation information indicates that the area of oil and gas mainly from two major hydrocarbon source rock sections:Shashi formation upside-Xingouzui group under section, migration processes with near oil source, a short distance transporting features. Jiangling sag Wancheng fault zone have Xingouzui and Qianjiang two transportation systems,including sand transportation system, section transport system and fault and permeability of sand composite petroleum system.(5) Wancheng fault thought to be the the most favorable oil and gas accumulation zone by analysising the fault reservoir-cap combination, trap conditions, main factors of oil and gas migration.Because Wancheng fault is near the Meihuaiqiao sub-sag, oil source is adequate.Among them,the Caixue block,the Fu I fault block and the northern Wan 5x well area is the most favorable area. |
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