On the feasibility of inducing oil mobilization in existing reservoirs via wellbore harmonic ﬂuid action
Although vibration-based mobilization of oil remaining in mature reservoirs is a promising low-cost method of enhanced oil recovery (EOR), research on its applicability at the reservoir scale is still at an early stage. In this paper, we use simpliﬁed models to study the potential for oil mobilization in homogeneous and fractured reservoirs, when harmonically oscillating ﬂuids are injected/produced within a well. To this end, we investigate ﬁrst whether waves, induced by ﬂuid pressure oscillations at the well site, and propagating radially and away from the source in a homogeneous reservoir, could lead to oil droplet mobilization in the reservoir pore-space. We discuss both the ﬂuid pore-pressure wave and the matrix elastic wave cases, as potential agents for increasing oil mobility. We then discuss the more realistic case of a fractured reservoir, where we study the ﬂuid pore-pressure wave motion, while taking into account the leakage effect on the fracture wall. Numerical results show that, in homogeneous reservoirs, the rock-stress wave is a better energy-delivery agent than the ﬂuid pore-pressure wave. However, neither the rock-stress wave nor the pore-pressure wave is likely to result in any signiﬁcant residual oil mobilization at the reservoir scale. On the other hand, enhanced oil production from the fractured reservoir’s matrix zone, induced by cross-ﬂow vibrations, appears to be feasible. In the fractured reservoir, the ﬂuid pore-pressure wave is only weakly attenuated through the fractures, and thus could induce ﬂuid exchange between the rock formation and the fracture space. The vibration-induced cross-ﬂow is likely to improve the imbibition of water into the matrix zone and the expulsion of oil from it.