Study On The Physical Properties And Main Controlling Factors Of Coal Reservoir In Turpan-Hami Basin

The physical properties of coal reservoirs cover many aspects such as coal petrology,pore-fracture system,adsorption and seepage ability,heterogeneity,etc.The methods of reservoir physical property characterization are mainly conventional experiments such as Mercury Injection,Cryogenic Liquid Nitrogen,Isothermal Adsorption,etc.In recent years,unconventional methods such as NMR,X-CT,and Three-dimensional Geological Modeling have also been used.Xinjiang Uygur Autonomous Region has attracted much attention as an important area for the development of coalbed methane(CBM)industry after the Qinshui Basin,but it is only concentrated on the southern margin of the Junggar Basin,and it is urgent to explore some other key areas.Using conventional and unconventional methods to focus on the study of the physical properties of coal reservoirs in the Turpan-Hami Basin and their main controlling factors can provide reference and scientific basis for the evaluation and selection of CBM dessert.The coal seams in the Turpan-Hami Basin were formed in the Xishanyao and Badaowan period,and have obvious regional distribution characteristics.The fore-mountains zone in the northern margin and the southern and eastern depression are the main coal-accumulating areas.With the Liaodun uplift-Aidinghu slope as boundary,the coal seams in Badaowan Formation are mainly developed in the Taipei and Tuokexun sags,furthermore,the coal seams are gradually thinning from west to east.In the Xishanyao period,the Shaerhu and Dananhu depression were coal-accumulating centers with huge thick coal seams,and the coal were also deposited in Hami and Taipei area.The Ro value of the coal is generally lower than 0.6%,which means lignite and long-flame coal are the main ones,only the Aiweiergou appears gas coal.Coal macrolithotypes are semi-bright and semi-dark mostly.Based on the experimental analysis of MIP and LTNA,the coal samples include a variety of pore-fracture systems,which represent different storage and seepage capabilities,the pore type in the Shaerhu and Dananhu samples are mainly seepage pores,while the Aiweiergou and Sandaoling samples are composed of adsorption pores,the proportion of large pores in coal is gradually increasing from Aiweiergou area to the southern depression.Besides,primary pores and various of secondary pore-fracture can be found in the samples,which makes the coal samples in the southern depression area have strong seepage ability.Meanwhile,the phenomenon of mineral filling is also obvious.The average Langmuir's volume and Langmuir's pressure of coal samples are 11.43cm~3/g and 6.49MPa.The coal's Langmuir's volume of the Badaowan Formation is higher than that of the Xishanyao Formation.Through the NMR and Isothermal Adsorption experiments,we know that the coal samples in Sandaoling area have the greatest adsorption performance.The results of CT scan experiments shows that the average connected porosity of the samples was 2%,and the pore-fracture of the coal samples had obvious heterogeneity characteristics.The main controlling factors of the physical properties of coal reservoirs in the Turpan-Hami Basin include structural evolution,coal-forming environment,metamorphic grade,coal petrology and quality,etc.The superposition of multiple tectonic activities has common influence in the development of secondary pores and fractures,and different coal-forming environments have caused great differences in the quality of the coal samples.Because the Ro is lower than 0.6%,the relative content of microscopic components has a significant impact on the pore structure of coal and the adsorption capacity of coal reservoirs.