Miletić Marta, Küçükuysal Ceren, Gülcan Merve, Garcia Randy
Department of Civil, Construction, and Environmental Engineering, San Diego State University, San Diego, CA, USA.
Geological Engineering Department, Muğla Sıtkı Koçman University, Engineering Faculty, Muğla, Turkey.
Heliyon. 2024 May 24;10(11):e31844. doi: 10.1016/j.heliyon.2024.e31844. eCollection 2024 Jun 15.
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.
在水力压裂和水基强化采油作业过程中，水吸渗是储层岩石中的一个重要过程。然而，由于致密砂岩复杂的孔隙结构，包括纳米和微米级孔隙与喉道的存在、表面性质以及矿物学的广泛变化，其水吸渗行为尚未得到充分理解。本研究聚焦于自发水吸渗对致密砂岩孔隙度演化的影响。在此背景下，通过结合多尺度成像方法（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）以及分析技术（X射线衍射、傅里叶变换红外光谱、扫描电子显微镜-能谱仪和热重分析）对托里·巴夫砂岩岩心进行了表征。所研究的致密砂岩岩心孔隙度为12.3%，渗透率为2.05毫达西，含有石英（58%）、粘土（高岭石和伊利石，23%）、钾长石（7%）、白云石（7%）和方解石（5%）等矿物。大小分别为60至140微米和30 - 50微米的原生孔和次生孔大多填充有高溶解性碳酸盐矿物和亲水性伊利石，这影响了致密砂岩的自发水吸渗能力。多尺度成像技术表明，经过10小时的水吸渗实验后，致密砂岩的平均孔径增加了1.28%，在岩石-水接触处达到2.35%，在岩心顶部为0.13%。换句话说，在整个岩心中，水吸渗时的孔隙度变化并不均匀，而是呈现出几乎线性的趋势。这一观察结果可以通过高溶解性碳酸盐和亲水性伊利石对致密砂岩微观结构的显著贡献来解释。本研究表明，多尺度成像技术在研究自发水吸渗方面至关重要，有望在致密砂岩强化采油或水力压裂的进一步研究中发挥作用。
