Pre-Darcy flow revisited under experimental investigation

Abstract

Background: Sufficient literature has been published about Pre-Darcy flow in non-petroleum disciplines. Investigators dissent about the significance of deviation of Darcy's law at very low fluid velocities. Most of their investigations are based on coarse, unconsolidated porous media with an aqueous fluid. However little has been published regarding the same for consolidated oil and gas reservoirs. If a significant departure from Darcy's law is observed, then this could have multiple implications on: reservoir limit tests, under prediction of reserves, unrecognized prospecting opportunities etc. Methods: This study performs a comprehensive review of the literature. Experiments were conducted to confirm the presence and the significance of Pre-Darcy flow effect in petroleum rocks. Results: The review of literature and experiments indicate the presence of Pre-Darcy effect. Contributing factors to Pre-Darcy effect are discussed and some reasons causing this effect are postulated. The experiments also show that this effect is significant. Conclusion: Pre-Darcy effect is significant because it is the dominant flow regime in typical petroleum reservoirs.

Mesoscopic approach to fluid-solid interaction: Apparent liquid slippage and its effect on permeability estimation

“…The zero force intercept means the absence of threshold applied force [3,40], consistent with the slip length (and then the effective pore size) independence of body force as found above. Again our proposed LBM model does not recover the phenomena of the pre-Darcy effect [48][49][50] and threshold pressure gradient [51][52][53] observed in shale and clay.…”

“…(13). The proposed model does not recover the phenomena of the pre-Darcy effect [48][49][50] and threshold pressure gradient [51][52][53] in shale and clay, which, however, is consistent with the independence of slip length (and then the effective pore size) on body force.…”

“…Also, it is consistent with the independence of slip length (and then the effective channel size) on body force observed in our work. Thus, the phenomena of pre-Darcy effect (more than proportional increase) [48][49][50] and threshold pressure gradient [51][52][53] observed in shale and clay cannot be recovered by our proposed LBM.…”

“…The improved permeability estimation methods, such as the equivalent rock element model [44], the model for predicting petrophysical properties [45], and the fractal geometry theory [46,47], considered the irreducible water saturation. The adsorbed water layer may account for the following phenomena: (1) the pre-Darcy effect [48][49][50], in which the Darcy flux increases nonlinearly (more than proportionally) with the pressure gradient, and (2) threshold pressure gradient [51][52][53], below which the fluid does not flow. Longmuir [54] also attributed the non-Darcy behaviors to the quasicrystalline structure (equivalent to adsorbed water layer) due to the cohesive interaction between fluid molecules and solid surface, and offered a three-zone description for the low permeability reservoirs: (1) dead zone, (2) nonlinear seepage (pre-Darcy) zone, and (3) pseudolinear seepage (larger than threshold pressure gradient) zone.…”

Non-Darcy Skin Effect with a New Boundary Condition

“…It is generally used for modeling flow in petroleum reservoirs and aquifers, because the low-matrix permeability results in low velocities. At low velocities, Siddiqui et al (Siddiqui, Soliman, Waylon, & Akif, 2016) have already showed a deviation of Darcy's law which prevails away from the wellbore. However, higher velocities are often observed in fractures and near wellbores; a more complicated model is needed to describe flow in these cases.…”