| The gas occurrence is influenced by many geological factors which include geological structure,pressure,sedimentation and hydrology etc.And the main control factors in different regions are different.In these geological elements,hydrogeological conditions are the key control factors of gas enrichment in No.15 coal seam in S mine of Yangquan Coal Industry Group,which are characterized by large variation range of gas content and gas composition,large distribution of nitrogen zone and nitrogen-methane zone.Therefore,it is very important to study the groundwater system and its gas control mechanism.Therefore,by making full use of geological,seismic,logging and other multi-source information,the seismic and geological comprehensive interpretation method of underground aquifer system is studied.Firstly,under the guidance of seismic sedimentology theory,the high resolution sequence stratigraphic framework was constructed,and the sedimentary environment and spatial distribution characteristics of sand bodies before and after coal accumulation in No.15 coal seam were studied.Combined with the data of simple hydrology and water sample test,the logging interpretation of the aquifer,sandstone and limestone aquifer and their porosity and salinity are carried out.Finally,the study area is divided into two types of hydrogeological units,runoff area and retention area,based on the information of sealing ability and formation water salinity of aquifers and faults.The variation characteristics of gas content and composition in each hydrogeological unit are analyzed,and the control effect of hydrodynamic conditions on coal gas enrichment is preliminarily discussed.The main results are as follows:(1)The high-resolution sequence stratigraphic framework of coal measures strata in Taiyuan Formation is constructed based on the exploration and development geological and logging data of coalbed methane and coalfield in the study area.(2)By using seismic phase adjustment,slice,frequency division and seismic attribute interpretation techniques,the sand-to-ground ratio in the sequence before and after coal accumulation was optimized and predicted by seismic attributes,and the sedimentary microfacies and spatial distribution characteristics of sand bodies in PS3 and PS4 sequences before and after coal accumulation in No.15 coal seam were finely characterized.(3)According to the differences in lithology and structure of aquifer,combined with the logging response characteristics of lithology,sandstone porosity and limestone fractures,the porous sandstone aquifer and fractured limestone aquifer were identified in the PS3 and PS4 sequences of 58 wells,and the aquifer thickness and sandstone porosity were explained.(4)On the basis of logging curve pretreatment,the plane variation of formation water salinity was predicted by using natural potential parameters,and the runoff area and relative retention area were divided.The salinity of formation water in this area ranged from 1000 mg/ L to 2400 mg / L,and the salinity increased from east to west,which was consistent with the trend of coalbed methane enrichment.(5)Based on the comprehensive seismic geological interpretation results of structure,sedimentary facies,porosity,aquifer and its salinity,the control effect of structuresedimentation-lithology and physical property-hydrodynamic conditions on gas enrichment in No.15 coal seam is clarified.Four types of hydrological gas control units are synthesized.On this basis,four hydrogeological gas control areas are delineated in the whole region. |
PDF Full Text Request