A Study On Reservoir Characteristics And Reservoir-cap Assemblage In The Zifusi Sag

Jianghan Basin is located in Hubei province, central of the Jianghan Plain, an area of36,360square kilometers,which is a typical inland salt lake fault basin in east of China and can be divided into11depression and4salient. Jiangling depression lying in the Jianghan Basin southwest,is the largest secondary tectonic unit in Jianghan Basin. Jiangling Depression have the tectonic framework of block shape in north-west direction and stripe shape in north-east direction as Wancheng fault as the boundary,and it developed a number of the fault depression, overall showing the tectonic framework of more uplifs and more depressin. The tectonic evolution of Jiangling Depression is the same as Jianghan basin. According to the changes of tectonic stress background, structural evolution can be divided into three phases:Late Cretaceous-Early Eocene (K-E2) rift formation phase, Middle Eocene-Oligocene (E2-E3) rift formation phase and Neogene to Quaternary (N-Q) regional depression phase. Cretaceous-Paleogene of Jiangling sag is continental rivers-lakes sandstone depositional system, the Xingouzui group as the main hydrocarbon source strata. Zifusi sag is located in the eastern Jiangling sag has developed complete formation, including the Cretaceous Yuyang group,Paleogene Shashi group, Xingouzui group, Jingsha Group, Qianjiang Group, Jinghezhen group, the Neogene Guanghuasi group and the Quaternary Pingyuan group, mainly in clastic sediments.The center of work area in this research is Hudu River-Zifusi hydrocarbon generation sag, including the eastern section of Jingzhou anticline zone and the Gongan monoclinal structura zone. On the base of drilling coring report, logging date and seismic date,comprehensive utilization theory and approach of the sedimentology, reservoir geology, petroleum geology,geophysics and other disciplines related to the theory and research methods,focus on the reservoir characteristics, Cap rock condition, reservoir-cap assemblage and find out the favorable exploration area.First analyse characteristics of depositional system of Zifusi sag,including sedimentary facies characteristics and their distribution, and then study the microscopic of main sand body reservoir lithology, physical properties and pore structure characteristics, macro analysis of reservoir space distribution and the main purpose of the sandstone layer thickness distribution in the study area, and the reservoir performance is also evaluated. For there is possible beneficial volcano rock reservoir in the south of Zifusi, investigaing and researching sufficient survey about lithology identification, reservoir characteristics and reservoir evaluation, volcano rock reservoir-forming rules and other literature of volcano rock reservoir, summed up the technology and method of volcano rock reservoir research.Use of drilling, seismic, slice data to analyse the volcano rock facies, revealing the volcano rock reservoir is the main reservoir space types and reservoir property. Finally, contain the cover layer conditions to discusse the main combination of reservoir types and distribution of Zifusi sag, combined with the reservoir pattern to discuss effect how reservoir cap combination control on oil and gas accumulation, and find out the favorable exploration area.Major depositional systems in Zifusi sag Shashi-Xingouzui groups are the delta and lakes,develop the delta front, the shallow lake and semi-deep lake subfacies,the main reservoir is the delta front subfacies,almost sandstone reservoirs. Located in the upper Shashi formation, Xingouzui group under paragraph,Jingsha group and Qianjiang group. The main reservoir is located in Xingouzui groupunder the delta front facies sand body, wherein the underwater distributary channel and mouth bar microfacies sand body is the favorable oil and gas reservoir sand bodies, to III-IV reservoir, followed by the grade of reservoir. In addition the gold field and the North anticlinal belt near basalt volcano, formed large overflow facies reservoir, lithology with basalt, volcano activity in Jingsha formation scale is the largest, and is mainly distributed in Zifusi low-lying area north. Southern Jingjiachang field tectonic zones Xingouzui group of basalt, and with jiangshen4and adjacent to the jin4, jin6wells basalt reservoir thickness,has a certain exploration potential in Zhungeer basin, on the basis of volcano rock reservoir evaluation standard, will the volcano rock reservoir initial evaluation for IV-V level reservoir. Qianjiang formation oil shale, argillaceous rocks of Jingsha group, the " Gypsum layer","mud compartment and Shashi gypsum and salt rocks are effective cap.The main reservoir-cap assemblages are Shashi-Xingouzui groups which belong to self-generating and self-preserving and lower-generating and upper-preserving.Self-generation type combination is mainly developed in upper Shashi formation of the Xingouzui group, source rocks, mainly for the Xingouzui group, reservoir in Shashi group and Xingoouzui group under paragraph, cover layer is the Xingouzui group lower segment of the mud layer, large paste layer, which have great sealing ability. The combination of lower reservoir pattern is the main source zone, hydrocarbon source layer within a source near the source reservoir model, development and a portion of salt structure (Fu Xingchang structure, Shashi structure), fault block tectonics (Fan Jiatai structure, Chi Anjie structure,Jin Jiachang structure) related structure, mainly distributed in the Jingzhou anticline belt and the Gongan monoclinic belt. Lower-generating and upper-preserving combined mainly developed in the new nozzle group Jingsha formation (or Qianjiang), city group the source ability is not very good, therefore must be provided to the Jingsha formation reservoir accumulation of hydrocarbon source rocks. The structure is a near North West trending faults by salt uplift and jointly control the structure of the nose, communicating Xingouzui group and Jingsha formation, oil and gas are likely to be from the source rocks, and the lateral row to fault fault vertical migration to the upper reservoir for students gathered in upper reservoir secondary oil and gas reservoirs, mainly in Zifusi low-lying area.