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桃2区块位于鄂尔多斯盆地中北部,其马五_(1~4)亚段碳酸盐岩储层属于特低孔渗储层,发育裂缝。通过观察大量岩心,结合铸体薄片和岩心录井资料,主要从裂缝的产状及成因类型分别对该区马五_(1~4)亚段岩心宏观裂缝和镜下微观裂缝系统分类。研究区马五_(1~4)亚段储层岩心宏观裂缝主要见3类,即水平缝、垂直缝和斜交缝,其中水平缝最常见,其次是垂直缝,斜交缝所占比例最小;马五1~1和马五1~3中的垂直缝较其他小层发育;马五_1~4小层的斜交缝最发育。裂缝主要出现在粉晶云岩和含泥云岩中。镜下微观裂缝类型主要有构造微裂缝、溶蚀缝和成岩缝等。研究发现:未充填或不完全充填的垂直缝和斜交缝对马五_(1~4)亚段储层渗流作用有较大影响;微裂缝喉道是主要的喉道类型之一,开启的微观裂缝与溶孔或溶洞的充填残余孔及晶间孔配合形成的孔洞缝组合对储层的有效性有很大贡献。气藏开发实践证明,有效的碳酸盐岩裂缝是该区气井在五_(1~4)亚段高产的关键性地质因素。
The peach 2 block is located in the north-central Ordos Basin. The carbonate reservoir in the Ma5-1 (subscript 1-4) sub-region belongs to the ultra-low porosity and permeability reservoir and develops fractures. By observing a large number of cores and combining the data of casting thin slices and core logs, the macroscopic and microscopic fracture systems of the cores in sub-section Ma5-1 (subscript 1-4) in this area are mainly classified according to their occurrence and genetic type. There are mainly three kinds of macroscopic fractures in the reservoir cores of the sub-section Ma5_ (1 ~ 4) in the study area, namely horizontal seam, vertical seam and diagonal seam, of which horizontal seam is the most common followed by vertical seam and oblique seam While the vertical seams in Mawu 1 ~ 1 and Mawu 1 ~ 3 developed more than those in other subfamilies. The diagonal seams of Mawu_1 ~ 4 were the most developed. Cracks mainly occur in the pink crystal dolomite and muddy dolomite. Microscopic types of microscopic cracks mainly include structural microfractures, dissolution fractures and diagenetic fractures. It is found that the vertical and diagonal seams without filling or incomplete filling have a great influence on the seepage of the Ma5-1 (1-4) sub-layer. The micro-fracture throat is one of the main throat types, Of the micro-cracks and dissolved pores or cave filling hole and intergranular hole with the hole formed by the combination of the reservoir effectiveness of a great contribution. The practice of gas reservoir development proves that the effective carbonate fractures are the key geological factors for the high-yielding of the gas wells in the Wu-1 ~ 4 sub-region.