四川盆地须家河组低渗透气层渗透率模型的建立

A permeability model built up on low permeability gas reservoirs in Xujiahe formation, Sichuan basin

四川盆地上三叠统须家河组发育大量低渗透气层,不同层位孔渗关系不同,常规建模方法得到的渗透率不能代表储层真实情况,这给储层评价带来了困难。为了建立适合低渗透气层的渗透率模型,从反映孔隙结构的毛细管压力资料出发,通过对Thomeer模型的求解,找到了有效渗流孔隙与无效渗流孔隙分界点。该点反映了控制流体流动的主孔隙系统,代表了非润湿相完全占据有效孔隙空间时的状态。将岩心渗透率与该点交会,分层段建立了反映孔隙结构的渗透率模型。将新模型应用于实际储层进行检验,结果表明新模型精度较高,值得推广。

Since there is a lot of low permeability gas reservoirs developed in Xujiahe formation in the Sichuan basin and different horizons has different porosity-permeability relationship, it is hard for permeability got by conventional modeling method to represent the real situation of a reservoir, which brings lots of difficulties to reservoir evaluation. In order to establish a permeability model suitable for low permeability gas reservoirs, from capillary pressure data reflecting pore structure and by solving the Thomeer model, the demarcation point, reflecting main pore system controlling fluid flow and representing the state when nonwetting phase occupies effective pore completely, is found out between effective seepage pore and ineffective seepage pore. A permeability model is established zone by zone which reflects that pore structure after core permeability is intersected with demarcation point. It is proved that this new model has relatively higher accuracy and worthwhile to be extended further when it is examined in actual reservoirs.