Study On Shale Features Of Wufeng Formation-longmaxi Formation In Dejiang Area Of Guizhou

This paper takes the Wufeng-Longmaxi Formation black shale in the Dejiang area of northeastern Yunnan as the main research object.Based on the predecessor data,the authors discuss the Wufeng Formation-Longma River in the Dejiang area through the measured stratigraphic profiles,field routes and sample test analysis data.Group shale mineral composition,sedimentary facies characteristics,and physical properties.For organic-rich shales,the geochemical characteristics of organic matter were studied and the abundance of original organic matter was restored.At the same time,the shale gas exploration potential in the Dejiang area was analyzed by comparison with the organic-rich shales in the neighboring area.?1?The brittle minerals in the Wufeng-Longmaxi shale are mainly quartz and feldspar,and the quartz content is positively correlated with the TOC value.The clay minerals are mainly illite and Eimon mixed layers,and the clay minerals are negatively correlated with TOC values.The lithology from the bottom to the top of the Wufeng Formation is grayish yellow-grey green mudstone,black mudstone,and the upper segment?guanyinqiao?argillaceous limestone;the lower segment of the Longmaxi Formation is black mudstone,the upper muddy siltstone,and calcareous siltstone.In the study area,the Wufeng Formation-Longmaxi Formation continental sedimentary facies sedimentary system shows that the deep water shelf and the shallow shelf shelf alternately appear.?2?The organic matter type of the organic-rich shale in the Wufeng Formation-Longmaxi Formation is dominated by I,and a small amount is II1.The thermal evolution Ro values are mainly distributed in 1.64².03%,which is a period of high maturity,condensate gas-moisture.The organic matter abundance of organic-rich shale is 0.9-7.35%,the TOC-value of non-black shale is 0.01-0.5%,the TOC of the lower part of Wufeng Formation gradually increases,and the bottom of the Longmaxi Formation is TOC.The value gradually decreases.Selecting 2.23 as the recovery coefficient of the original organic matter,the restored organic-rich shale TOC values range from 2.12 to 16.39%.The non-black shale has a low TOC value and has little significance after recovery.?3?Adsorption desorption curves of shale were measured by nitrogen adsorption experiments,and adsorption desorption curves were analyzed in detail.The pore morphology of shale in the study area was determined to be the pores and slit pores in the inner wall of the parallel crevice.The main shape,both ink bottles.The BET specific surface area of the shale reservoir was measured to be in the range of7.1265¹9.2223m²/g,and the BET total pore volume was in the range of 0.0077⁰.0234ml/g.There was a linear relationship between the specific surface area and the total pore volume.The pores mainly include intergranular skeleton pores,dissolved pores,interlaminate pores in clay aggregates,mold pores,organic pores,diagenetic shrinkage fractures,and interlaminar page joint fractures.Porosity values were distributed from 3.98 to 7.99%.Permeability is mainly distributed in0.0008⁰.0078×10^-3?m²??4?The adsorption amount of shale is not only controlled by TOC,but also the content of clay mineral has a great influence on it.The amount of adsorption of different minerals is also different.There are also great differences in the hydrocarbon generation ability of different organic matter types.Generally,Type I has the strongest hydrocarbon generation ability,followed by Type II,Type III has the lowest hydrocarbon generation ability,and TOC value is positively correlated with gas-bearing capacity.The higher the degree of evolution,the more micropores within the organic matter increase,and the specific surface area increases correspondingly,which increases the adsorption of organic-rich shale.In the study area,the influence of conservation conditions on gas content is mainly reflected in three aspects:tectonic movement,roof and floor characteristics.Tectonic uplifting changed the buried depth of the Wufeng-Longmaxi Formation shale,and the resulting fractures and fractures destroyed the original sealability of the shale,resulting in the loss of shale gas;the top and bottom plates had a closed effect on shale gas,and the roof and floor Different lithology,its compressive ability is also very different,and the capping ability of the capping zone is not as deep as the capping.The organic-rich shale in the study area has a thin thickness,shallow burial,and fracture development,resulting in poor self-sealing of shale gas and having no commercial development value.