页岩的储层特征以及等温吸附特征

Shale reservoir characteristics and isothermal adsorption properties

页岩的储层特征以及吸附特征是评价页岩气是否具有开采价值的一个重要标准,为此,以某页岩气藏为例,测量其岩心的孔隙度与渗透率,并进行X射线衍射全岩分析和黏土矿物测定,以分析其储层特征。结果表明:该页岩的孔隙度主要分布在0.01%～5%,渗透率主要分布在0.000 01～10mD,孔隙直径主要分布在4～6nm;页岩的孔隙度与渗透率没有明显的相关关系,黏土矿物主要为绿泥石、伊利石、蒙皂石以及伊蒙混层。挑选了6块岩心进行等温吸附试验,以确定TOC以及Ro对页岩吸附能力的影响,结果表明:①页岩的气体吸附遵循Langmuir等温吸附曲线,其总解析气量与页岩的TOC成正相关,但与孔隙度没有明显的关系;②不同成熟度、不同TOC页岩的吸附特征研究表明,页岩的吸附能力与页岩的TOC和Ro密切相关,随着页岩TOC以及Ro的提高,页岩的吸附能力增加;当页岩的TOC相近时,页岩的Ro越高,吸附能力越强;当页岩的Ro相近时,页岩的TOC越高,页岩的吸附能力越强。

Shale reservoir characteristics and isothermal adsorption properties is one of the major criteria for the judgment on the commercial exploitation of shale gas.In a case study of a shale gas reservoir,the porosity and permeability of its core samples were measured at first,then the whole rock analysis was made and clay minerals were identified by the X-ray diffraction method,which aimed to analyze the reservoir characteristics.From the results,the porosity of shales is ranged from 0.01% to 5% while the permeability is 0.00001-10 mD and the diameter of pores are 4-6 nm.No obvious relationship could be shown between porosity and permeability of shales,and the clay minerals mainly include chlorite,illite,smectite,and illite-montmorillonite mixed-layer minerals.Additionally,6 core samples were selected for the isothermal adsorption tests to determine what impact the TOC content and Ro have on the adsorption ability of shales.The following results are obtained.(1) Shale gas adsorption follows the rules of Langmuir isothermal adsorption curves,the total gas content has positive relativity to the TOC content of shales but is not related to the porosity.(2) An investigation into the features of adsorption of shales with different maturity degrees and different TOC contents demonstrates that the adsorption ability of shales is closely related to the TOC content and Ro,the rising of which will result in a higher adsorption performance of shales.In particular,for the shales with a similar TOC content,the higher the Ro,the higher ability of adsorption;while for the shales with a similar Ro,the higher the TOC content,the higher ability of adsorption.