Coal Reservoir Modeling And The Optimization Of Favorable Development Blocks In Anze Block Of Qinshui Basin

The study area,Anze is located in the southwestern of Qinshui Basin,where the Qinhe,Sihe and Lanhe are developed.The main coal seam is the No.3 coal of the Permian Shanxi Formation.The fine geological structure interpretation of the study area was performed using well logging and 2D seismic data which covers a ground area of 1115 km~2.The structural model and multi-attribute models of the No.3 coal seam in the Anze block were built by superimposing the surface model and the fault model.Besides,the distributions of several reservoir physical properties were analyzed.Based on the study of the main controlling factors of coalbed methane(CBM)enrichment,an integrated evaluation system was established on the foundation of geological conditions and the criteria for the classification of favorable areas to optimize the most favorable target area for further CBM development in the Anze block.Based on well data and seismic data,a velocity model was established.Through the results of synthetic seismogram to calibrate the top and bottom of the No.3 coal seams,and through these comprehensive interpretation methods,more than 50 faults were identified,and mostly are high-angle normal faults.Besides,fine geological modeling of No.3 coal seam in the study area was conducted to predict the buried depth and coal thickness.The northeast and southeastern corners of Anze block are deep buried areas with a maximum depth of 1690 m,which is shallower from east to west.The total coal thickness ranges from 0.8 to 8.4 m with an average of 5.96 m.Using multi-seismic attribute analysis techniques,four properties such as RMS and Frequency were extracted to characterize the distribution of coal porosity.Combined with seismic analysis technology and logging methods,three types of coal structure were identified and the coal structure distribution of the study area was predicted.The stochastic simulation method was used to predict the distribution of porosity and permeability in coal reservoirs.The result shows that porosity ranges from 0.01%to 4.94%;the permeability was between 0.002~0.48 md and the value of permeability is controlled by the tectonic structural zone.Considering the four aspects of hydrocarbon source,reservoir conditions,preservation,and resource to analyze the main controlling geological factors of CBM enrichment in the Anze block,it was found that as the burial depth increases,the gas content increases;the higher the ash content,the lower the gas content;in the coal-bearing areas where the tectonic movement is intense,the coal-bed gas was dissipated in a large amount,and gas content decreased.When the thickness of overlying mudstone reaches over 8 m,the value of gas content is generally higher than 12 m~3/t.With the comprehensive evaluation methods including Analytical Hierarchy Process,correlation fitting and grey relational analysis,we considered coal thickness,depth,coal quality,thickness of overlying mudstone,reservoir pressure,and critical desorption pressure in the study area to predict the favorable area in the Anze block.According to the value of comprehensive evaluation parameter W,the study area is divided into four parts,and the most favorable area I(W?0.75)mainly distributed in the area near the well Q14-4 in the central and eastern of the study area.