| Porous carbonate reservoirs are common in petroleum exploration. Taken as examples from porous dolostones in Sichuan and Tarim basins, the texture of different pore systems in classical dolostone reservoirs, including intergranular 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 commonly 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 porosity and permeability. |
