Characteristics Of Organic-rich Shale Of Middle Devonian Luofu Formation In Guizhong Depression

With the sustained and rapid development of China's economy and society and the adjustment of energy structure,the demand for natural gas and other clean energy sources has increased rapidly and substantially,and the contradiction between energy supply and demand has become increasingly prominent.The emergence and development of shale gas have brought hope to solve the energy crisis.Due to its huge resource potential and economic benefits,shale gas has been valued by people.Shale gas refers to the natural gas that exists and accumulates in the shale stratum rich in organic matter in the form of adsorption and free state.Guangxi mud shale is widely dispersed,upper palaeozoic,the residual organic matter abundance,moderate degree of thermal evolution,hydrocarbon generation potential is tremendous,petroleum geology characteristic and the sichuan basin gas shale is similar to the it will very likely to study the distribution of shale gas exploration breakthrough in guangxi region,to open up a new field of natural gas exploration in guangxi region.In research,on the basis of predecessors'research data,sedimentology,sedimentary geochemistry,seismic stratigraphy and other disciplines theory as the instruction,on the basis of field geological investigation,combined with the indoor synthetic analysis,system conducted in GuiZhong depression of devonian series Luo Fu formation of rich organic matter sedimentary background of the development of mud shale petrological and mineralogical characteristics of organic geochemical characteristics,and optimizing the favorable exploration area.Based on detailed study on a large number of field section,combined with the recognition of various sedimentary facies marks,will GuiZhong region in the devonian series is divided into two sedimentary basin and carbonate platform facies,and further to open platform,the isolated tableland,stage basin,such as the types of sedimentary facies,and describes in detail the sedimentary microfacies characteristics and time-space distribution,depositional model is established.The study area is dominated by Taiwan basin,with open platform to the north of daliang-luocheng area and isolated platform to the south of litang-shilong area.The content of organic matter rich shale in luofu formation of GuiZhong depression ranged from 24%to 97%with an average content of 56%.Feldspar minerals were dominated by plagioclase with an average value of 7%.The average clay mineral content was 35%,the highest was 71%,and the lowest was 3%.Clay minerals are mainly illite,followed by kaolinite and chlorite.Generally speaking,it has the component characteristics of high quartz and low carbonate rock minerals.The thickness of mud shale in luofu formation is deeper than 250m,and the organic carbon content is deeper than 2.0%,accounting for 76.4%,and the samples greater than 3.0%,accounting for 43.6%.The kerogen macronutrients are mainly sapropelite and chitinite.The overall performance is type I-II₁ organic matter,and the maturity of organic matter generally ranges from 2%to 2.5%,with good hydrocarbon generation conditions.The mud shale of luofu formation has a variety of pore types and developed micropores and micro-fractures,providing a good storage space for the occurrence of shale gas.The organic carbon content in the Nandan-Hechi area in the northwest of the middle devonian luofu formation and the Shanglin-Heshan area in the south of the study area is between 1%and 4%,the thickness of the shale is 250-500m,the maturity of the organic matter is between 2-2.8%and locally higher than 3%,which has a good hydrocarbon generation potential and is a favorable exploration area for shale gas in the middle of Guangxi.