关键词: Low permeability Pore surface mineralogy Segmentation Spontaneous capillary imbibition Tight sandstone X-ray computed tomography

来  源:   DOI:10.1016/j.heliyon.2024.e31844   PDF(Pubmed)

Abstract:
Water imbibition is an important process in reservoir rocks during hydraulic fracturing and water-based enhanced oil recovery operations. However, the water imbibition behavior in tight sandstones has not been fully understood due to their complex pore structure, including the presence of nano and micron-sized pores and throats, surface properties, and wide variation in mineralogy. The present study focuses on the effect of spontaneous water imbibition on the porosity evolution of a tight sandstone. Within this context, a core of Torrey Buff sandstone was characterized by using a combination of multiscale imaging methods (X-ray Computed Tomography, Scanning Electron Microscopy), laboratory experiments (porosity-permeability measurements), and analytical techniques (X-ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy-Energy Dispersive Spectroscopy, and Thermogravimetry). The studied tight sandstone core has a porosity of 12.3 % and permeability of 2.05mD with minerals of quartz (58 %), clays (kaolinite and illite, 23 %), K-feldspar (7 %), dolomite (7 %) and calcite (5 %). Primary and secondary pores, ranging in size from 60 to 140 μm and 30-50 μm, respectively, are mostly filled with highly-soluble carbonate minerals and hydrophilic illite, which influence the spontaneous water imbibition capacity of the tight sandstone. The multiscale imaging technique indicates that after a 10-h long water imbibition experiment, the average pore size of the tight sandstone increased by 1.28 %, reaching 2.35 % at the rock-water contact and 0.13 % at the top of the core. In other words, throughout the core, the porosity changes upon water imbibition are not uniform but show an almost linear trend. This observation could be explained by the significant contribution of highly-soluble carbonates and hydrophilic illite on the microstructure of the tight sandstone. This study implies that multiscale imaging techniques, crucial in examining spontaneous water imbibition, hold promise for further research in enhanced oil recovery or hydraulic fracking in tight sandstones.
摘要:
渗吸是储层岩石在水力压裂和水基强化采油作业中的重要过程。然而,由于其复杂的孔隙结构,致密砂岩中的吸水行为尚未得到充分理解,包括纳米和微米大小的孔和喉咙的存在,表面属性,矿物学的差异很大。本研究的重点是自发吸水对致密砂岩孔隙度演化的影响。在此背景下,TorreyBuff砂岩的核心通过使用多尺度成像方法(X射线计算机断层扫描,扫描电子显微镜),实验室实验(孔隙度-渗透率测量),和分析技术(X射线衍射,傅里叶变换红外光谱,扫描电子显微镜-能量色散光谱,和热重分析法)。研究的致密砂岩岩心的孔隙度为12.3%,渗透率为2.05mD,矿物为石英(58%),粘土(高岭石和伊利石,23%),钾长石(7%),白云石(7%)和方解石(5%)。初级和次级毛孔,尺寸范围从60到140μm和30-50μm,分别,大多充满高可溶性碳酸盐矿物和亲水性伊利石,这影响了致密砂岩的自发吸水能力。多尺度成像技术表明,经过10小时长的吸水实验,致密砂岩的平均孔径增加了1.28%,在岩水接触处达到2.35%,在岩心顶部达到0.13%。换句话说,在整个核心,渗水时孔隙度变化不均匀,但几乎呈线性趋势。这一观察结果可以通过高可溶性碳酸盐和亲水性伊利石对致密砂岩微观结构的重要贡献来解释。这项研究意味着多尺度成像技术,在检查自发吸水时至关重要,有希望在致密砂岩中进一步研究提高石油采收率或水力压裂。
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