Two-phase Fluid low in a Petroleum Reservoir
Whether the inherent ‘hysteresis’ in a petroleum reservoir – has really made it difficult – in order to develop – appropriate models of oil-water flow system – resulting from the failure of ‘capillary pressure – saturation’ relationship – to uniquely describe the drainage and imbibition scenarios - in an oil-water system?
OR
From thermodynamic perspective, whether the introduction of the ‘oil-water interfacial area surface’ - explicitly (i.e., projecting ‘interfacial area’ as a ‘state variable’ explicitly, in addition to saturation) – would efficiently describe the ‘capillary pressure function’ – by applying the extended form of Darcy’s law using momentum balance equations?
If so, will it eliminate the hysteresis effect completely in an oil-water petroleum reservoir system?
OR
Do we really require ‘Euler characteristic’ (topological invariant) – in order to uniquely describe an oil-water system – that produces ‘closure relations’ for models based on ‘continuum mechanics’?
OR
The transient/non-equilibrium and quasi-static/quasi-equilibrium ‘capillary pressure – saturation – interfacial area surface’ – would always remain statistically different – for each petroleum reservoir oil-water system; and subsequently, a single relationship – that remains independent of oil and water flow conditions – remains nearly ruled out?
Suresh Kumar Govindarajan
Is the hysteresis of the OFP really needed? If this is the initial stage of development, you can kill yourself over this topic, but in the end it will still be a finger in the sky. I see the benefit of this when there is real data on which all this can be reproduced, or at worst, if there is a strong discrepancy in production between the wells and predictions according to the model built for the OFP impregnation, taking into account that the saturation beats to perfect. I worked in a field where all wells started with 10-50% water and conventional phase impregnation gave good results. A strong hysteresis, in my opinion, will most likely be observed only in oil-wetted reservoirs.
Suresh Kumar Govindarajan
Answering your title question: the only way to eliminate hysteresis in a rock is to eradicate the interfacial tension between oil and water :-). When displacing oil with water, three main effects are to consider: the reversal of flow direction, wettability change and the build-up of residual oil saturation (isolated, trapped blobs of oil). Concerning capillary pressure hysteresis, reservoir numerical simulators can only scale it automatically with the oil residual saturation. Therefore, if oil is displaced by water (aquifer or water injection), it is important to load a so-called imbibition curve beside the drainage curve. Yuri Mirgorod is correct; it is more critical in oil-wetted reservoirs. Complex reservoirs with a high body-to-throat ratio will also show a larger difference between drainage and imbibition. If you have time, check our paper SPE-192758-MS: New Model for Wettability Change with Depth in Mixed-Wet Complex Carbonates.
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