Creep behavior of marine Wufeng–Longmaxi Formation shales in the Sichuan Basin, Southwest China characterized at micro scale: A case study of exploration well SQ-1 in Sanquan Town, Nanchuan District, Chongqing

IF 4.2 3区 工程技术 Q2 ENERGY & FUELS
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Abstract

Creep behavior is a very important attribute of shale and is crucial in the design of hydraulic fracturing schemes to ensure the long-term stable development of shale gas. However, how different shale minerals, organic matter, bedding planes, and pores affect the micro-creep behavior of Upper Ordovician Wufeng and Lower Silurian Longmaxi (WF–LMX) Formation shales is poorly understood. In this study, we employed a nanoindentation mechanical testing technique alongside rock mineralogical, major elemental, and pore analyses to investigate the creep behavior and influencing factors of WF–LMX shales at the microscale. The results show that (1) the creep displacement (Δh) and indentation creep parameter (CIT) are each positively correlated with clay, total pore volume, and clay + total organic carbon (TOC) contents but negatively correlated with the content of quartz, excess SiO2, and TOC. We found weak or no correlation between the occurrence of minor rock constituents, such as feldspar, carbonates, and pyrite, and the shale creep properties; (2) the creep parameters (Δh, CIT, and stress exponent (n)) exhibit anisotropy due to the layering of shale, with values 7.3%–24.2% higher in the plane perpendicular to bedding (X1) than those in the plane parallel to bedding (X3). The creep displacement exhibits negative correlations with Young's modulus, hardness, and stress exponent (n), especially for the X1 direction; (3) compared with those of China's Yanchang shale, the stress exponents of WF–LMX shale are relatively high (8.5–30), indicating that the average creep capacity of WF–LMX shale is relatively weak. Overall, nanoindentation technology has shown great potential in studying shale creep and provides quantitative data support for macroscopic shale creep research.

中国西南四川盆地海相五峰-龙马溪地层页岩微尺度蠕变行为特征:重庆市南川区三泉镇 SQ-1 号勘探井案例研究
蠕变行为是页岩的一个非常重要的属性,对于设计水力压裂方案以确保页岩气的长期稳定开发至关重要。然而,不同的页岩矿物、有机质、层理和孔隙如何影响上奥陶统五峰组和下志留统龙马溪组(WF-LMX)页岩的微蠕变行为却鲜为人知。本研究采用纳米压痕力学测试技术,结合岩石矿物学、主要元素和孔隙分析,在微尺度上研究了 WF-LMX 页岩的蠕变行为及其影响因素。结果表明:(1) 蠕变位移(Δh)和压痕蠕变参数(CIT)分别与粘土、总孔隙体积和粘土+总有机碳(TOC)含量呈正相关,但与石英、过量 SiO2 和 TOC 含量呈负相关。我们发现长石、碳酸盐和黄铁矿等次要岩石成分的存在与页岩蠕变特性之间的相关性较弱或没有相关性;(2)蠕变参数(Δh、CIT 和应力指数(n))因页岩的分层而呈现各向异性,垂直于基底面(X1)的蠕变参数值比平行于基底面(X3)的蠕变参数值高 7.3%-24.2%。蠕变位移与杨氏模量、硬度和应力指数(n)呈负相关,尤其是在 X1 方向;(3)与中国延长页岩相比,WF-LMX 页岩的应力指数相对较高(8.5-30),表明 WF-LMX 页岩的平均蠕变能力相对较弱。总之,纳米压痕技术在页岩蠕变研究中显示出巨大潜力,为页岩宏观蠕变研究提供了定量数据支持。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Natural Gas Industry B
Natural Gas Industry B Earth and Planetary Sciences-Geology
CiteScore
5.80
自引率
6.10%
发文量
46
审稿时长
79 days
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