Research On Geological Characteristics Of Shale Gas In Longmaxi Formation In Well B1 Of High-steep Structural Belt In Eastern Sichuan

Well B1 is located in the daershan structure in the high and steep structural belt in the east of Sichuan basin.The drilling purpose of this well is to explore the gas bearing property of the reservoir of LongMaXi formation of silurian?ordovician wufeng formation,to carry out the formation and reservoir situation of daershan structure,and to pre-explore the fluid bearing situation of this area,so as to provide a basis for the block evaluation and well location deployment.In the collection on the basis of predecessors'research results and regional geological data,this paper,by using seismic,drilling,logging,well logging and thin section,core and laboratory analysis test data,the B1 well creek,the dragon group stratigraphic features,sedimentary facies characteristics,organic matter and the reservoir characteristics and so on to carry out comprehensive study,thus clear well B1 creek,the dragon group of shale gas geology characteristics.The main achievements of this paper are as follows:(1)Based on logging,well logging and core data,the correlation and division of small shale strata in LongMaXi formation were carried out.The strata from longyi-1 sub-member to wufeng formation were well matched with the block of pyroshiba,but the thickness was slightly different.The sedimentary facies study shows that the sedimentary microfacies of well B1 can be compared with that of the block of coke rock dam.It is pointed out that the sedimentary microfacies of siliceous and argillaceous deep-water continental shelf in the reduction environment is conducive to the accumulation and preservation of organic matter,and is the most favorable sedimentary facies belt for shale gas reservoirs.(2)According to the organic geochemical analysis data,the organic carbon content of the 1-submember wufeng formation of well longyi in B1 is high;Good organic matter type,mainly 1 type;Has reached the mature stage,mainly dry gas generation,hydrocarbon generation potential is strong.(3)According to the core description,drilling results,logging interpretation results and various analytical and laboratory data,the mineral composition characteristics,organic geochemical characteristics,lithofacies characteristics,physical characteristics,storage and permeability space characteristics,and gas-bearing characteristics of shale reservoirs are analyzed,and the reasons for low porosity and poor gas-bearing properties of the Wells are analyzed.The analysis of reservoir characteristics shows that:well B1 longyi 1 submember?wufeng formation belongs to the reservoir with high brittle mineral content,low clay mineral content,low porosity,extra low permeability,low gas content,and the pore type is dominated by fracture-shaped hole,wedge or v-shaped hole,and the reservoir is comprehensively evaluated.(4)For the first time,the "TOC+mineral components" two-step method was used to divide the lithofacies of longyi section and describe the characteristics of each lithofacies.It is pointed out that the organic rich siliceous shale facies and the organic rich carbonate-siliceous shale facies are the most favorable petrofacies for shale gas exploration because of their high organic carbon content and brittle minerals.