Stapf Siegfried, Shikhov Igor, Arns Christoph, Gizatullin Bulat, Mattea Carlos
Department of Technical Physics II, University of Technology Ilmenau, PO Box 100 565, 98684, Ilmenau, Germany.
School of Minerals and Energy Resources Engineering, University of New South Wales, Sydney, NSW, 2052, Australia.
Magn Reson Lett. 2023 Mar 8;3(3):220-231. doi: 10.1016/j.mrl.2023.02.001. eCollection 2023 Aug.
In reservoir rocks, the term "ageing" refers to extended exposition to crude oil; a typically water-wet sandstone will then gradually become oil-wet as a consequence of the deposition of insoluble fractions of oil onto the surface grains. Rocks have been aged artificially by subjecting them to a bitumen solution at elevated temperature in order to achieve comparable surface properties for three different types of rock: Bentheimer, Berea Buff and Liège Chalk. Using saturated and aromatic model compounds as proxies for crude oil, the nuclear magnetic resonance (NMR) relaxation dispersion in native and aged rocks was compared and correlated to the properties of paramagnetic impurities in these rock types. Perfluorated liquids were found to follow the same trend as deuterated and naturally occurring oil components, suggesting they can be used as suitable tracers for wettability studies since the F nucleus is absent in natural sources. By combining electron paramagnetic resonance (EPR) and dynamic nuclear polarization (DNP) it becomes possible to identify and quantify the origin of the dominating relaxation processes between native and aged rocks, providing an alternative approach to assess wettability in natural rocks.
在储层岩石中，“老化”一词指的是长时间暴露于原油中；典型的水湿砂岩会因原油不溶成分沉积在表面颗粒上而逐渐变为油湿。为了使三种不同类型的岩石（本特海默砂岩、贝雷亚浅黄色砂岩和列日白垩岩）具有可比的表面性质，已通过在高温下使其接触沥青溶液来对岩石进行人工老化。使用饱和和芳香族模型化合物作为原油的替代物，比较了天然岩石和老化岩石中的核磁共振（NMR）弛豫色散，并将其与这些岩石类型中顺磁性杂质的性质相关联。发现全氟液体与氘代和天然存在的油成分遵循相同的趋势，这表明它们可作为润湿性研究的合适示踪剂，因为天然来源中不存在氟原子核。通过结合电子顺磁共振（EPR）和动态核极化（DNP），可以识别和量化天然岩石和老化岩石之间主要弛豫过程的起源，为评估天然岩石的润湿性提供了一种替代方法。
