| Shales of the Ordovician Wufeng Formation,Lower Silurian Longmaxi Formation,Lower Cambrian Niutitang Formation and Sinian Doushantuo Formation in the Sichuan Basin and its surroundings are important strata for shale gas exploration in my country.The existing exploration results are mainly for the shale of the Longmaxi Formation,which has good shale gas storage conditions,and there are relatively few studies on the Niutitang Formation,especially the Niutitang Formation in the Upper Yangtze Block.Shannanye 1 well is located on the northwestern edge of the Yangtze block,belonging to the Micang Mountain uplift,structurally located in the Dazhuba-Huijunba complex syncline area,and geographically located in Huijunba Village,Xiaonanhai Town,Nanzheng County,Hanzhong City,Shaanxi Province.Preliminary geological surveys indicate that this area has a certain potential for shale gas resources.In order to obtain the shale gas evaluation parameters and gas-bearing characteristics of the Lower Cambrian Niutitang Formation in the southern Shaanxi area,the first parameter well in the Nanzheng area of Shaanxi Province is based on the relevant data of the Shaannan Page 1 well,combined with the sample laboratory Analyzing the test results,a systematic analysis and research on the geological conditions such as the sedimentary environment background,shale gas generation conditions and spatial characteristics of shale gas occurrence of the Niutitang Formation in Ye 1 Well in Southern Shaanxi were carried out.The depth of the core samples from Shannanye 1 well ranges from 2158.60m to2388.19m,including three rock types:gray-black mudstone,black carbonaceous shale,and black carbon-containing siliceous shale.Through chloroform asphalt"A"analysis,organic carbon content(TOC)analysis,organic matter maturity analysis(measurement of asphalt equivalent vitrinite reflectance),whole rock X-ray diffraction analysis,clay mineral X-ray diffraction analysis,microscopic component analysis,Analysis and test data of scanning electron microscopy analysis,overburden porosity and permeability experiment,etc.show:(1)The Niutitang Formation of Shannanye 1 well has good shale gas enrichment and preservation conditions.Through scanning electron microscopy analysis,3categories and 5 categories of pore types were observed,namely mineral matrix pores(including intergranular framework pores,dissolution pores and matrix intercrystalline pores),organic pores and microcracks.These microscopic pores are in varying degrees Provides abundant space for shale gas storage;the available porosity and permeability results range from 0.02%to 5.17%and 8.24×10-4m D to 5.36m D.The remaining samples are below the detection limit,which is low Low porosity-ultra-low permeability reservoirs are conducive to the preservation of shale gas.(2)The Niutitang Formation of Shannanye 1 well has good conditions for shale gas generation.The organic matter has a high degree of maturity,with Ro between2.48%and 3.36%,which is in the stage of dry gas generation;the organic carbon content is average,with an average value of 1.5%,mainly residual organic carbon.In view of its stable supply and shortage of land-based sources Oxygen-reduced sedimentary environment,it is considered that the original organic matter abundance conditions are good;the microscopic components of the microscopic composition are mainly saprolite amorphous bodies with a higher degree of evolution,and no inert bodies and crustaceous groups are found,and kerogen types are not found.It is type I,with strong hydrocarbon generation ability of the parent material.(3)The main factors affecting the gas-bearing properties of the shale in the Niutitang Formation of Shannanye 1 well include the abundance of organic matter,the maturity of organic matter,and the depth of burial.The total gas content generally shows an increasing trend with the change of depth,which indicates that the deeper the burial,the more beneficial to the preservation of shale gas;the total gas content is positively correlated with the abundance of organic matter,indicating that the higher the abundance of organic matter,the greater the impact on shale gas.The stronger the enrichment capacity of shale gas is;the higher the gas content of shale gas is when the total gas content is within the maturity range of 2 to 3%,which is conducive to the generation of shale gas.The depth of the“sweet spot”of the Niutitang Formation in Shannanye 1 well is mainly located between 2180-2230m and 2270-2360m,which is the key horizon for follow-up research.Based on the data analysis of the shale gas geological conditions of the shale in the Niutitang Formation in Shannanye 1 well,the author believes that the Lower Cambrian Niutitang Formation is a high-quality page between the southern margin of the Hannan Paleo-Continent and the Micangshan Uplift in southern Shaanxi.The rock is relatively stable,with large thickness,relatively high abundance of organic matter,suitable burial depth,moderate maturity,and good shale gas generation conditions;abundant occurrence space and good shale gas preservation conditions;carbonaceous siliceous shale is used as an example Mainly,the content of brittle minerals is relatively high,which is conducive to fracturing production;the gas content is generally high,which is a preferred area suitable for exploration and development. |
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