孔隙型储层的孔隙系统三维量化表征——以四川、塔里木盆地白云岩为例

以四川盆地和塔里木盆地孔隙型白云岩样品为例,通过CT扫描、数字岩心、分形与多重分形等方法,讨论了典型白云岩储层不同孔隙系统(如晶间孔、粒间孔、铸模孔等)的结构特征,并用定量化参数对孔隙结构进行数值表征。结果表明:晶间孔和粒间孔样品的孔隙形状多为三角形,孔隙相对细长,喉道发育,连通性较好;铸模孔样品的孔隙形状较为规整,二维平面上表现为圆形,三维空间上近似球体,这类样品往往孔隙较为发育,但是孔喉系统连通性差;由多种类型孔隙组成的"混合孔"样品则非均质性较强,受岩石组构特征影响显著。进一步利用分形与多重分形方法对孔隙的非均质性进行研究发现:不同孔隙类型的结构差异在分形盒子维数上有明确响应,维数的均值相对大小表现为:铸模孔粒间孔晶间孔混合孔。孔隙度可能也对盒子维数产生影响。

3D Quantitative Characterization of Pore Systems in Porous Reservoirs:Cases of Porous Dolostones in Sichuan Basin and Tarim Basin

Porous carbonate reservoirs are common in petroleum exploration. Taken as examples from porous dolo-stones in Sichuan and Tarim basins, the texture of different pore systems in classical dolostone reservoirs, including in-tergranular pores, intercrystalline pores, moldic pores, etc. are analyzed and discussed, and then the structures of pores and throats are quantitatively characterized in 3D space by high-resolution micro-nano CT scan, digital core technique and fractal and multi-fractal methods. The result has shown that intergranular pores and intercrystalline pores are com-monly triangle in shape and radial in 3D space and pores are relatively long with developing throats which lead to well connectivity for whole rock. Moldic pores are regular in shape and almost circular in 2D space but sphere in 3D space. In this type of samples, big pores are usually corresponded to high porosity but the poor connectivity of pore and throats which lead to low permeability. Mixed pores present obviously heterogeneity and influenced by fabric and composition of carbonate rock. It is shown that Dbox values and regularity index of pore shapes have different response to different pore systems. The Dbox values exhibit a descending order of moldic, intergranular, intercrystalline and mixed pores from the maximum to the minimum values. Additionally, porosity maybe influence Dbox values according to analysis of poros-ity and permeability.