Log Interpretation Method Of Coalbed Methane Hydrological Storage Unit In Gujiao Mining Area,Xishan Coalfield

The hydrologic unit in the CBM reservoir is an important factor affecting the CBM enrichment.This paper takes the No.2 and No.8 coal seams in the Gujiao Mining Area of Xishan Coalfield as the research object,and quantitatively explains the water content of the aquifer and the groundwater flowability through logging.According to the aquifer thickness,resistivity and porosity,the study area was divided into high water-bearing area and low water-bearing area;the study area was divided into relative runoff area and relative detention area by the aquifer mineralization degree.Finally,the multi-factor superposition method was used to divide the study area into beneficial units,more favorable units,and unfavorable units for coalbed methane hydrologic storage,and to conduct inspection of the storage units in combination with the gas content of coal in each unit.Concluded as follow:(1)Based on the correction of the logging data environment in the study area,the coal-bearing strata are divided into three third-order sequences and nine fourth-order sequences,finally establishing the sequence stratigraphic framework for the three or four levels of the study area;Based on the grid,the natural potential,natural gamma,and resistivity logging curve combination method was used to finely explain the sequence of sandstones 2# and 8# andthe sandstone aquifer and limestone aquifer in the adjacent sequence.(2)The degree of salinity is a key parameter for characterizing hydrodynamic conditions.The natural potential method is used to calculate the resistivity of formation water.Based on the statistical relationship between the salinity of produced water in the CBM well and the resistivity of the formation water,a suitable formation water reservoir is obtained.The degree of well logging calculation method;calculation of the Shanxi Formation and the Taiyuan Formation coal-bearing formation water salinity;the Taiyuan Formation coal-bearing aquifer mineralization degree is higher than that of the Shanxi Formation;the calculated mine according to the logging The degree of correlation with the measured gas content was analyzed.With the increase of salinity,the gas content also increased.(3)Aquifer thickness,sandstone porosity,and limestone resistivity are used as the boundary of the water system.The study area is divided into high water content areas(the thickness of the aquifer in the Shanxi Formation is more than 6m,the thickness of the Taiyuan Formation aquifer is more than10 m,and the porosity is more than 12).%,L1 limestone resistivity> 800?·m)and low water content zone(the Shanxi Formation aquifer thickness <6m,Taiyuan aquifer thickness <10m,porosity <12%,L1 limestone resistivity<800? · m);Using the salinity as the boundary of the flow system,the study area was divided into relative stagnation areas(the salinity of the Shanxi Formation is >1200 mg/L,the Taiyuan Group salinity is >1400 mg/L)and therelative runoff zone(the Shanxi Formation salinity is <1200 mg/L.L,Taiyuan group mineralization degree <1400mg/L).The multi-factor superposition method was used to classify the coalbed methane hydrological storage units into three categories: favorable units,relatively favorable units,and unfavorable units.Comparing the actual gas content data of coalbed gas wells in each unit,it is found that the favorable gas content is highest in the unit,followed by the relatively favorable unit,and the lowest coal gas content in the unfavorable unit.