用核磁共振测井资料评价碳酸盐岩等复杂岩性储集层

Description of carbonate reservoirs with NMR log analysis method

对于碳酸盐岩等复杂岩性油气藏,由于其储集空间复杂、非均质性强等因素,用常规测井技术难以进行准确描述.核磁共振测井测量的对象是储层空间中的流体,因而可以直接用来划分储集层,而且能提供几乎不受岩性影响的孔隙度和渗透率等参数;同时,由于其T2分布表征了岩石的孔隙结构,所以可以根据T2分布形态判断有效裂缝和溶蚀孔洞.通过多口井的岩心对比和成像测井对比,研究出了一套用MRIL和CMR的T2分布形态评价储集空间的方法;此外,在特定条件下,根据核磁计算的有效孔隙度和可动流体体积给出了一个计算含油饱和度的公式.利用这些核磁测井技术及其分析方法对车古20古潜山碳酸盐岩储集层裂缝及溶蚀孔洞发育特征进行准确描述,还计算了埕北潜山复杂复杂岩性油气藏的饱和度,对于储量计算具有重要意义.

Conventional log technology is difficult to evaluate correctly some complex reservoirs which are characterized with complicated pore space, special lithology and inhomogeneous layers such as conglomerate reservoir, carbonate reservoir, igneous reservoir and so on, it is necessary to resort to some high-technology logs. As a base of new theory, nuclear magnetic resonance （NMR） log can provide accurate porosity which is little dependent of lithology, so it can be used for reservoirs identifying. Characterizing porosity structure, T2 distribution of NMR can be used to identify valid fractures and vugs and a series of rules are summarized as a table. Furthermore, at special conditions without water in reservoirs, the ratio value of movable fluid volume and total porosity maybe regard as oil saturation. With these methods, characterization of fractures and vugs are described in Chegu 20 Buried-Hill carbonate reservoirs, and oil saturation of carbonate reservoirs of Chengbei zone is calculated, which is profound for accurate reserves.