Fractal Analysis of Shale Pore Structure of Continental Gas Shale Reservoir in the Ordos Basin, NW China

详细信息    查看全文

• 作者：Fujie Jiang ; Di Chen ; Jian Chen ; Qianwen Li ; Ying Liu ; Xinhe Shao ; Tao Hu ; Jinxiong Dai
• 刊名：Energy & Fuels
• 出版年：2016
• 出版时间：June 16, 2016
• 年：2016
• 卷：30
• 期：6
• 页码：4676-4689
• 全文大小：868K
• 年卷期：0
• ISSN：1520-5029

文摘

Describing the characteristics of shale pore structure is vital for the assessment of shale reservoir, which has significant influence on the storage and seepage mechanisms of gas shale. To profoundly understand the shale pore structure characteristics of continental shale reservoir, fractal analysis was performed on 45 continental shale samples from the Ordos Basin, NW China, via low-pressure N₂ adsorption experiments. The characteristics of N₂ adsorption isotherms revealed that slit-shaped shale pores are dominant among the geometric shapes of shale pores. During N₂ molecules adsorption process, different characteristics were displayed at two regions where relative pressures (P/P₀) were 0–0.45 and 0.45–1. The Frenkel–Halsey–Hill (FHH) method was used to calculate fractal dimensions (D) at these two regions. In addition, the fractal exponents “(D – 3)/3” and “(D – 3)” were compared adequately. The results show creditable fractal characteristics for continental shale. Fractal exponent D – 3 is more suitable for the calculation of the fractal dimension in the study area. The surface fractal dimension (D₂₁) and pore structure fractal dimension (D₂₂) were further investigated. Results indicate that D₂₁, ranging from 2.04 to 2.50, was affected by shale constituents and provided a site for gas shale adsorption. D₂₂ reflects the irregularity and heterogeneity of the shale structure, varying from 2.20 to 2.65, and is higher overall than D₂₁. Furthermore, the value of D₂₂ negatively correlates with the average diameter of the shale. In addition, the comparisons of shale pore structure characteristics between the reservoirs Chang-7 and Chang-9 show that the shale pore structure of Chang-9 reservoir is more irregular and nonhomogeneous and is favorable for gas shale storage but unfavorable for seepage.