利用小角中子散射表征页岩闭孔结构与演化  

The Structure and Evolution of Closed Pores in Shale Determined by Small Angle Neutron Scattering

作　　者：张林浩 徐嫣然 孙梦迪 蒋恕 张钰莹[1,2] Chunming Wu[3] 张介辉 梁兴 王高成 ZHANG LinHao;XU YanRan;SUN MengDi;JIANG Shu;ZHANG YuYing;Wu Chunming;ZHANG JieHui;LIANG Xing;WANG GaoCheng(Key Laboratory of Tectonics and Petroleum Resources,Ministry of Education,China University of Geosciences,Wuhan 430074,China;China University of Geosciences(Wuhan),Wuhan 430074,China;Australian Centre for Neutron Scattering,ANSTO,NSW 2234,Australia;PetroChina Zhejiang Oilfield Company,Hangzhou 311100,China)

机构地区：[1]构造与油气资源教育部重点实验室,武汉430074 [2]中国地质大学(武汉),武汉430074 [3]澳大利亚中子散射中心,新南威尔士洲悉尼市2234 [4]中国石油浙江油田分公司,杭州311100

出　　处：《沉积学报》2021年第2期310-323,共14页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(41802146,41690134);中国石油天然气集团公司重大现场试验项目“深层页岩气有效开采关键技术攻关与试验”(2019F-31)。

摘　　要：随着页岩孔隙网络结构表征更加精细与定量化,页岩中闭孔含量、结构与演化引起了广泛关注。为研究页岩的闭孔特征,通过小角中子散射、氮气吸附、高压压汞和氩离子抛光—场发射扫描电镜等实验手段对四川盆地威201(W201)井中下志留统龙马溪组页岩、上奥陶统五峰组页岩和下寒武统筇竹寺组页岩中的闭孔含量及孔隙结构进行了测定,同时分析了闭孔的演化规律。实验结果表明,W201井页岩在三个层位中均有闭孔发育,且闭孔的发育均与有机孔隙网络体系有关。发现五峰龙马溪组页岩所测得的分形维数与闭孔率存在良好地正相关性。对于三个层位深度的纵向分析发现,随着深度的增加页岩压汞闭孔率逐渐升高,其主要原因是随着页岩孔喉的变化,小孔喉不断消失,汞可充注的孔喉下限将会增大。通过对比氮气吸附和小角中子散射的结果显示W201井的闭孔孔径从大到小依次为五峰组页岩、龙马溪组页岩和筇竹寺组页岩。对页岩储层中闭孔特征的研究可以为评价页岩储层的储集性和渗透性提供新的思路,在页岩油气的勘探与开发中也具有重要的地质与工程意义。With the development of increasingly precise and quantitative characterization of shale pore network structures,the content,structure and evolution of closed pores in shales has attracted widespread attention.To study the closed-pore characteristics of shale,methods such as small angle neutron scattering(SANS),low pressure N_(2)adsorption(LPNP),mercury injection capillary pressure(MICP),argon ion polishing field emission scanning electron microscopy(AIP-FESEM)and other methods were used to determine the content and structure of closed pores in the early Silurian Longmaxi Formation,the Upper Ordovician Wufeng Formation and the early Cambrian Qiongzhusi Formation shale in well W201,Sichuan Basin.The experimental results show that closed pores are developed in all three formations at well W201.Their development is related to the organic pore network system.A good positive correlation was found between the fractal dimension and the closed porosity of Longmaxi shale in the Wufeng Formation.Analysis of the depth of the three formations showed that,with increasing depth,the percentage of closed pores in shale gradually increases when measured by MICP,the main reason being that,as shale pore throats change,the smallest throats disappear,thus raising the lower limit of the amount of mercury that can fill the pores.By comparing the results of LPNP and SANS,the closed pore sizes at well W201 descend in an orderly manner in shale from all three formations.This study of the properties of closed pores in shale reservoirs provides a new idea for evaluating the storage capability and permeability of shale reservoirs,and also has important geological and engineering significance in shale oil and gas exploration and development.

关 键 词：闭孔 小角中子散射 流体注入法 孔隙结构 海相页岩 

分 类 号：P618.13[天文地球—矿床学]