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Understanding fluid distribution and displacement in porous media is essential for optimizing oil recovery in carbonate reservoirs (Hamza et al., 2023). It is reasonable to claim that direct observation of microscopic details—especially access to fluid topology within the pore space and its real-time evolution in situ—has greatly enhanced the understanding of multiphase flow in porous media and offered valuable insights into rock wettability (Pak et al., 2023).
In this context, this study examines the spontaneous imbibition process in coquina, a carbonate rock considered analogous to one of the facies from the pre-salt reservoir in Brazil. Using time-resolved X-ray microtomography, we monitored fluid displacement and distribution at the pore scale during different stages of oil production, considering the rock’s saturation conditions: dry, water-saturated, oil-aged, and in contact with recovery water. Micro-CT images were segmented at each
condition and time interval, enabling a detailed analysis of porosity profiles, fluid saturation, and phase occupancy maps. The contact angle test was also performed on the oil-aged sample immersed in formation brine to validate image observations related to reservoir condition restoration. The test initially indicated an oil-wet condition following the aging process.
Over time, the fluid saturation profiles within the sample pores suggest a shift in rock wettability corresponding to different stages of oil production. After the aging process, the wettability of the coquina shifted toward neutral or water-wet conditions, as indicated by the onset of spontaneous imbibition and the water occupancy profile within the pore space.
Additionally, the study identified a preferential pathway for fluid flow, shedding light on the dynamics of multiphase displacement in carbonate formations. Another important observation was the influence of viscous and capillary forces, as the oil stored in nanopores and micropores could not be recovered with this brine. This indicates that the recovered oil was initially stored in macro- and mesopores. These findings improve our understanding of fluid dynamics in pre-salt analogs and other valuable insights for optimizing oil recovery strategies.
| References | Hamza, A, Hussein, I.; Mahmoud, M. Chapter 1 - Introduction to reservoir fluids and rock properties - Developments in Petroleum Science, Elsevier, Volume 78, 2023. doi.org/10.1016/B978-0-323-99285-5.00003-X Pak, T.; Archilha, N. L.; Berg, S.; Butler, I.B. Design considerations for dynamic fluid flow in porous media experiments using X-ray computed micro tomography – A review. Tomography of Materials and Structures, V.3. 2023. doi.org/10.1016/j.tmater.2023.100017. |
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| Country | Brasil |
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