Petrophysical characteristics of shales with different lithofacies in Jiaoshiba area, Sichuan Basin, China: Implications for shale gas accumulation mechanism
Petrophysical characteristics of shales with different lithofacies in Jiaoshiba area, Sichuan Basin, China: Implications for shale gas accumulation mechanism
复制标题
四川盆地焦石坝地区不同岩相页岩岩石物理特征及其对页岩气成藏机制的启示
DOI：
10.1016/j.marpetgeo.2019.06.028
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发表时间：
2019-11-01
影响因子：
4.2
通讯作者：
Long, Shiyu
中科院分区：
文献类型：
--
作者：
Yang, Feng;Xu, Shang;Long, Shiyu
非常规储层的岩石物性特征对油气的储运有重要影响。本文对四川盆地焦石坝地区下志留统龙马溪组26个不同岩相的页岩样品进行了研究。孔隙网络（形态、孔隙度和孔隙结构参数）采用扫描电镜、氦气比重测定法和低压气体吸附技术进行了全面表征。渗透率系数由平行于层理样品的脉冲衰减测量得出。分析了页岩孔隙形态、孔隙度、孔径、孔径分布和渗透率的地质控制因素，建立了渗透率和控制气体流动的孔喉孔径的定量关系。根据其矿物学特征，总结了三种主要岩相：硅质岩相、泥质/硅质混合岩相和泥质页岩岩相。孔隙率、比表面积、孔容等孔隙结构参数与总有机碳含量呈正相关。有机质孔隙占硅质页岩孔隙度的67%，而无机孔隙占泥质页岩孔隙度的55%。klinkenberg校正的渗透率范围在0.01 ~ 46.4 μ D之间，由粘土薄片的排列控制。TOC含量与孔隙度、渗透率呈负相关。硅质页岩渗透率一般最低，而定向粘土片发育的泥质页岩渗透率相对较高。利用Winland相关性估计的渗漏孔孔径范围为9至476 nm。这些数值远高于氮吸附分析（吸附-孔径）得到的结果。所研究页岩的渗孔孔径与总粘土矿物含量呈幂相关关系。采用裂缝模型（片）来预测基于渗孔孔径的绝对渗透率。预测结果是合理的，证明了片层模型和渗流孔隙度的应用是合理的。硅质页岩TOC含量高，孔隙度和比表面积大，渗透率低，有利于天然气的保存。
The petrophysical characteristics of unconventional reservoirs have significant impacts on hydrocarbon storage and transport. In this study, 26 shale samples with various lithofacies from Lower Silurian Longmaxi shales in the Jiaoshiba area of Sichuan Basin are investigated. The pore network (morphology, porosity, and pore structure parameters) is comprehensively characterized using scanning electron microscopy, helium pycnometry, and low-pressure gas adsorption techniques. Permeability coefficients are derived from pulse-decay measurements on parallel to bedding samples. Geological controls on the pore shape, porosity, pore size, pore size distribution, and permeability of the shales are analyzed, and quantitative relationships with which to estimate the permeabilities and pore-throat apertures controlling gas flow are developed.Three general lithofacies are summarized in view of their mineralogy: siliceous, argillaceous/siliceous mixed, and argillaceous shales. Pore structure parameters (porosity, specific surface area, and pore volume) show positive correlations with total organic carbon (TOC) content. Organic matter-hosted pores contribute to approximate 67% of the porosity of siliceous shales, while inorganic matter contributes to 55% of the porosity of argillaceous shales. Klinkenberg-corrected permeabilities range between 0.01 and 46.4 mu D, and are controlled by the alignment of clay flakes. Negative relationships exist between TOC content, porosity, and permeability values. Siliceous shales generally have the lowest permeabilities, whereas the argillaceous shales with developed oriented clay flakes have relatively high permeabilities. The seepage-pore apertures, estimated using the Winland correlation, range from 9 to 476 nm. These values are much higher than those obtained from nitrogen adsorption analysis (adsorption-pore apertures). A power correlation exists between seepage-pore apertures and total clay minerals content of shales studied. A fracture model (sheet) is used to predict absolute permeability based on seepage-pore apertures. The predictions are reasonable, and justify the application of the sheet model and seepage-pore apertures. The siliceous shales are featured by a high TOC content, large porosity and specific surface area, and low permeability, which are favorable to gas preservation.