利用核磁共振技术确定有机孔与无机孔孔径分布——以四川盆地涪陵地区志留系龙马溪组页岩气储层为例  

Quantitative evaluation of organic and inorganic pore size distribution by NMR: A case from the Silurian Longmaxi Formation gas shale in Fuling area,Sichuan Basin

作　　者：李军[1,2] 金武军[1] 王亮[3] 武清钊[1] 路菁[1] 郝士博[1] 

机构地区：[1]中国石化石油勘探开发研究院,北京100083 [2]中国石化石油勘探开发研究院页岩油气富集机理与有效开发国家重点实验室,北京100083 [3]西南石油大学,四川成都610500

出　　处：《石油与天然气地质》2016年第1期129-134,共6页Oil & Gas Geology

基　　金：中石化科技部攻关项目(P13112)

摘　　要：页岩有机孔隙具有强烈亲油性，无机孔隙具有强烈亲水性。基于页岩孔隙润湿性差异，利用核磁共振技术（NMR）确定有机孔隙和无机孔隙孔径分布。步骤如下：将页岩岩心分别在饱和油与水条件下进行核磁共振观测，确定有机孔隙和无机孔隙横向弛豫时间（疋）分布谱，再利用高压汞注入与液氮吸附联测实验，建立砭时间与孔径大小定量关系（rd=52T2），以此为基础确定有机孔和无机孔孔径分布。将这一方法应用于四川盆地涪陵地区志留系龙马溪组页岩孔隙评价中，页岩有机孔直径集中分布在2～50nm，峰值为10nm，少量有机孔直径分布在200—500nm。无机孔直径分布范围较宽，分布在2．5—500nm，峰值为50nm。微裂缝尺寸较大，分布在4～10μm，峰值为5μm。应用FIB—SEM识别孔隙类型及其孔径分布，并检验NMR确定的孔径分布，两者具有一致性。核磁共振技术可以进行岩心全直径测量，能较真实地反映地下页岩气储层有机孔与无机孔孔径分布，而且测量成本低，具有良好应用前景。The micro-pores present different wettability in shale gas. The organic pores are oil-prone wettability and the inorganic pores are water-prone wettability. Based on the differences of wettability between different pore types of shale, Nuclear Magnetic Resonance （NMR） T2 spectrum is used to determine the pore size distributions of both organic and inorganic pores. The specific procedures are as follows. Firstly, NMR experiments are performed separately on shale core samples saturated with brine and dodecane respectively to identify T2 spectra of the organic pore and the inorganic pore. Secondly,joint mercury injection capillary pressure （MICP） and liquid nitrogen adsorption experiments are carried out to establish the quantitative relationship between T2 and pore-diameter distribution（ ra = 52T2 ）. Finally ,this formula is used to determine the pore size distribution of organic pore and inorganic pores. These methods are applied to the evaluation of the pore size distribution of the shale gas reservoir in the Silurian Longmaxi Formation in Fuling area, Sichuan Basin. The diameters of organic pores are mainly distributed in the range of 2 - 50 nm with a peak at 10 nm,and some are in the range of 200 - 500 nm. The inorganic pores show a wider range of diameter, i. e. 2.5 nm - 500 nm, with a peak at 50 nm. The micro-cracks show the largest size scale and range from 4 μm to 10 μm in width,with a peak at 5μm. The pore size distributions derived from NMR coincide with that derived from FIB-SEM quantitative analysis. NMR experiment can measure the whole core and thus can reflect the real in-situ pore size distributions of organic pores and inorganic pores of gas shale. Moreover, the cost of NMR measurement is low, thus demonstrates a good application prospect in gas shaleevaluation.

关 键 词：核磁共振 有机孔 无机孔 页岩气 龙马溪组 涪陵地区 四川盆地 

分 类 号：TE122[石油与天然气工程—油气勘探]