Evaluation Of The Capability Of The Impermeable Gas Barrier In The High-Frequency Sequence Framework Of The Late Permian Coal System In The Qianxi Area

Thesis takes the widely developed Impermeable gas barrier in the study area as the research object,aiming to complete the comprehensive evaluation of their sealing performance.Based on the theories and methods of petrology,sedimentology,sequence stratigraphy and geophysical logging,through the petrology characteristics,vertical sedimentary sequence,porosity and permeability parameters and geophysical data of the two basic wells in the study area,the logging identification template of water and gas barrier layers in the study area is developed The horizontal distribution pattern and sealing performance evaluation of water and gas barriers within the high-frequency sequence framework.Through petrology analysis,the macroscopic identification characteristics of water and gas barrier in the study area are summarized.Based on the physical property test results of core and related samples in the basic dry drilling in the study area,and geophysical data,the development characteristics of water and gas barrier are summarized.Cluster analysis method is used for the basic dry well to carry out correlation analysis with the apparent resistivity(LL3)data after removing the samples with abnormal high values of natural gamma(GR),The results show that the GR and LL3 response characteristics of the fourth type of data and the water resistant gas layer are very similar.A geophysical response feature based on the water resistant gas layer has been established,and a water resistant gas layer logging identification template has been comprehensively verified with its sedimentary environment information.It has been applied to the identification of water resistant gas layers in other silent wave time difference(AC)logging data drilling in the study area.Based on the measured data of water and gas barrier samples and the morphological identification results of siderite,the distribution laws of four stable primary water and gas barrier layers and nine relatively stable secondary water and gas barrier layers are traced in the high frequency sequence stratigraphic framework of the late Permian coal measures in the study area.The effects of geophysical logging response,the development difference of siderite layers in the sequence framework and sea level changes on the lateral difference of water and gas barrier layers are comprehensively discussed.A logging recovery model was established for the porosity,permeability,and breakthrough pressure of the water and gas barrier layers,constrained by the measured physical parameters of the samples.The sealing performance of each water and gas barrier layer was evaluated.Based on the grey correlation analysis method,the thickness,porosity,permeability,breakthrough pressure,and sequence framework position of the water and gas barrier layer are selected as the core evaluation indicators.Combined with the evaluation index weights obtained by the Analytic Hierarchy Process,the fuzzy mathematics method is used to comprehensively evaluate the single layer sealing performance of the water and gas barrier layer in the research area,The results show that the evaluation results of the sealing performance of each water and gas barrier layer in the study area are basically good,and the sealing performance of the first level water and gas barrier layer is generally better than that of the second level water and gas barrier layer.On the regional level,the sealing performance of the water and gas barrier layer in the core of the Panguan syncline and the southeast wing is strong,and the evaluation results reach level B or above,while the sealing performance of the northwest wing of the syncline is relatively weak.Thesis has 49 figures,40 tables and 161 references...