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As production declines from mature basins, Operators exploit tighter gas (0.1 md and less) reservoirs. These tight reservoirs require significantly more capital than conventional gas reservoirs to fully exploit the reservoir. In contrast to high permeability gas reservoirs where a well may drain 1 or more sections and the recovery of 90-95% is limited by the abandonment pressure,tight gas reservoirs may require 32 wells per section and yet recovery may approach only 60% of the original gas in place (OGIP). Exploiting these reservoirs requires an understanding of the petrophysical cutoffs to determine the true OGIP, the permeability distribution to identify the number of wells required and the placement of these wells and well fracture effectiveness.
Epic has performed several tight gas studies. In one of the studies on 3500 shallow gas wells, we identified the potential OGIP to be twice the original estimate (approximately 1 Tcf), built and history matched the permeability fields within the reservoir, provided estimates of incremental versus accelerated recovery for the 600 planned infills and estimated the effect of the surface pipeline restrictions on the productivity of the new infills and existing wells.
See Epic Written Papers on Gas Reservoirs
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Pressure profile shows undrained gas reserves within 1 section of a tight gas reservoir
Original interpretation of permeability in top image with revised interpretation after history matching in bottom image
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