Characteristics Of High-Frequency Sequence Stratigraphy Of The Late Permian Coal In The Zhina Area Of Western Guizhou And Its Influence On The Development Of Mud Shale

As one of the cleanest energy sources,shale gas has attracted much attention in its host carrier mud shale reservoirs.Based on the field geological survey and drilling data processing of the Upper Permian strata in the Zhina area of western Guizhou,this thesis starts with sequence stratigraphy,sedimentary petrology,paleontology and Milankovitch theory,and uses software such as Matlab to establish a high-frequency sequence in the Zhina area.Frequency sequence stratigraphic framework,systematically analyzed the depositional environment in the sequence framework,the development characteristics and laws of shale reservoirs,and then discussed the influencing factors of shale pore structure,and obtained the following results:(1)Based on profile measurement and core observation,there are 3 types of sedimentary facies,7 types of sedimentary subfacies and 13 types of sedimentary microfacies developed in the Upper Permian coal-bearing strata in the study area.The sequence interface was identified on the drilling section,and four third-order sequences were divided.The SQ1～SQ4 sequence sedimentary facies distribution map was drawn based on the sand-to-formation ratio results of each sequence.Depending on sea level changes,delta,lagoon-tidal flat,and carbonate platform depositional environments are distributed from west to east.The distribution characteristics of mud shale in both vertical and plane directions show that TST is the most developed layer of mud shale,with SQ1-TST and SQ3-TST being the most obvious.(2)Perform spectrum and wavelet analysis on GR logging data based on Mie cycle theory,determine the optimal wavelet transform scale values of a=34,86,321 in the study area;and extract the Mie cycle in the formation,combined with the base level cycle Division the Upper Permian strata are divided into 8 to 15 mid-term cycles to establish 4 high-frequency sequence stratigraphic frameworks.The validity of the highfrequency sequence stratigraphic framework is determined by analyzing the depositional time period.It is jointly controlled by factors such as global sea level change,basin subsidence,sediment supply and paleoclimate change;14 shale distribution maps under the fourth-order sequence were further drawn,and the shale affected by sea level is mainly developed in the study area.North-South line and Southwest.(3)The shale samples were analyzed by XRD,TOC,SEM&EDS and other experiments based on modern testing techniques.The results showed that:(1)The organic carbon content of shale has a large vertical span,and the TOC value in the lagoon-tidal flat environment is higher than that in the delta environment.The shale mineral composition is complex and diverse,and the brittle conditions are general,mainly including clay minerals,quartz,etc.According to SEM,the organic matter pores,intergranular pores and There are four types of pores including intercrystalline pores,intragranular pores and microcracks.(2)According to the combined experiment of mercury intrusion and liquid nitrogen,the pore volume is divided into 3 types and 1form.It is determined that the shale is mainly composed of nano-pores smaller than 110 nm,and the pore size below 5 nm contributes most of the specific surface area.(4)Based on the distribution position of shale samples in the high-frequency sequence stratigraphy,it is found that the high-frequency sequence has a great influence on the mineral composition and TOC content of shale;The results show that TOC has a great contribution to the total pore volume of shale,especially the micropore pore volume and the specific surface area of shale in the lagoon-tidal flat environment;clay minerals,especially chlorite The pore volume and specific surface area of shale have a greater contribution.This thesis has 93 figures,15 tables and 142 references.