由于煤岩样易碎,很难通过室内实验获得煤层真实的渗透率;煤岩弹性模量低,泊松比高,对应力十分敏感,地面条件下实验的渗透率不能反映地下的情况;常用的测井物性解释方法在煤层渗透率解释中很难应用.这些因素导致煤储层地质建模不能照搬常规砂岩油气藏的方法.依据试井确定渗透率,并通过渗透率影响因素的分析,分煤岩类型建立了渗透率与地应力的定量关系.提出了四步建模法:首先建立煤储层空间格架模型,然后建立煤岩相(类型)模型和地应力模型,在三者的约束下,通过井点试井渗透率和地应力井点计算渗透率的控制,采用随机模拟技术完成渗透率模型的建立.通过矿场实际数据的检验,模型与生产状况吻合比较好,证明该建模思路与方法在实际应用中可行.
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 re-veal the subsurface conditions,since the coal rock is low in elastic modulus,high in poisson's ratio,and thus it is sensi-tive to stress;(3) it is difficult to apply the methods of well log petrophysical interpretation to interpret coalbed permeabil-ity.Thus in this study,we determine the permeability via well testing data,and establish a quantitative relationship be-tween in-situ stress and permeability according to the types of coalbed,based on the analysis of all critical factors for per-meability.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 estab-lished 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.