鄂尔多斯西部天然气储层的孔隙特征

The Characteristics of Pores of Lower Ordovician Natural Gas Reservoir in West Eerduosi

通过对鄂尔多斯西部地区下奥陶统碳酸盐岩天然气储层的孔隙特征及孔隙发育规律进行的统计研究,发现该区碳酸盐岩储层中有13种孔隙类型。其中,白云石晶间溶孔和晶间孔为最主要的储集空间,溶蚀孔和溶洞是不可忽视的重要储集空间,各种成因的裂缝亦较发育,桌子山组的细晶白云岩是该区最主要的储集岩,它厚度大,分布稳定,赋存各种孔、洞、缝,面孔率高,具备良好的储集、运移条件,是天然气勘探的理想层段。决定该区天然气储层最终孔隙面貌的是成岩-构造事件。对储集空间贡献最大的是白云石化作用,其次是淡水淋滤溶蚀作用和构造破裂成缝作用。这三种成岩-构造作用在储层垂向上控制孔隙层段的发育程度,在横向上控制孔隙层段的规模大小和分布规律。

Through experiment and statistical analysis, 13 types of pore are found in the lower Ordovician carbonate reservoir of natural gas in the west Eerduosi. Among them, dolomite intercrystalline solution pores and intercrystalline pores are the most important reservoir space and solution pores and cavities—a relatively important one. Besides, there are many kinds of fracture in the reservoir. The fine crystalline dolostone in Zhuozishan formation, having many kinds of pore and fracture, is a dominant reservoir in this area. For its large and stable thickness and high porosity, the rservoir is an ideal stratum for natural gas exploration. Its porosity is controlled by diagenesis. The dolomitization, fresh water leaching process, dissolution and fracture-formed process came to the main reservoir space. The vertical and horizontal distribution of the pore-bed is governed by the above-mentioned diagenetic types.