Whether the permeability enhancement resulting from swelling of shale expansion has NO use at all?
Background:
Shale expansion from swelling increases the resultant over-burden stress in the vertical direction, and thereby leads to significante micro-fracturing in the horizontal direction; and in turn, enhances the resultant permeability of the shale reservoir.
However, this enhancement in permeability results at the expense of reducing the enhanced pore-fluid pressure; and hence, it may probably lead to sloughing and/or other drilling related problem.
Thus, I am NOT sure about the real benefit of experiencing this enhanced permeability associated with the swelling of shale expansion. However, this volume expansion of shale can be effectively mitigated by striking a balance among the following factor: (a) enhancing the drilling rate; (b) using the oil-based mud (that maintains the reservoir pore-pressure without losing it and thereby reduces the induced instability) as against using the water-based mud; (c) following under-balanced drilling; (d) cooling the mud (that induces the reservoir shrinkage; and in turn; mitigates any enhancement in over-burden stress); and (e) the selection of proper chemical composition of the drilling fluid.
What I've hears mostly about shale, is concerning about finding some way in order to reduce shale swelling, so i think the negetive results of this effect are more dominant than the positive one
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