Abstract: The way of coalbed geology modeling is quite different from that of modeling conventional sandstone oil/gas reservoirs due to the following factors.(1)It is difficult to obtain the actual permeability of coalbed through laboratory experiment because the coal rock sample is brittle;(2)the permeability derived through laboratory experiments cannot reveal the subsurface conditions,since the coal rock is low in elastic modulus,high in poisson's ratio,and thus it is sensitive to stress;(3)it is difficult to apply the methods of well log petrophysical interpretation to interpret coalbed permeability.Thus in this study,we determine the permeability via well testing data,and establish a quantitative relationship between in-situ stress and permeability according to the types of coalbed,based on the analysis of all critical factors for permeability.In addition,we propose a 4-step modeling,namely,to set up the model of coal reservoir space framework,the coal facies(type)model,and the in-situ stress model.Then,under these 3 constraints,the model of permeability is established with stochastic simulation technique and the controlling points from the permeability obtained from well test and well in-situ calculation.Further,the model fits well with the production data status quo from the actual coal data of bed methane fields,which proves the feasibility of the concepts and methods in practical application.

Key words: coal rock type, in-situ stress field, geology modeling, permeability, coalbed, Hancheng mining area, southeastern margin of Ordos Basin