Introduction
In tight formations that are water-wet in nature, the capillary forces cause liquid to be imbibed and held in the capillary pores. This causes the critical water saturation and irreducible water saturation to be high. As a result, liquid invasion into the rock matrix can be a major factor that causes low productivity in tight gas reservoirs and is sometimes classified as Wellbore Skin and Formation Damage . The amount of capillary pressure suction can hold imbibe and hold invaded water in-place. Additional reading can include the Permeability Jail concept.
Hydraulic fracturing in some cases may not improve well productivity in tight gas reservoirs, or the productivity may increase only temporarily. During the stimulation and fracturing in tight gas reservoirs, fracturing liquids invade the reservoir and may create a bank of fracturing agent around the hydraulic fracture wings, which can develop negative effects on the long term production performance of the well
The tight formations with sub-normal initial water saturation are significantly more sensitive to damage caused by water phase trapping, and therefore water blocking may plague the success of hydraulic fracturing in low permeability gas reservoirs with this characteristics
Additional Reading:
Coming Soon!
References:
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Hassan Bahrami, Evaluating Factors Controlling Damage and Productivity in Tight Gas Reservoirs, PhD Thesis, Curtin University, 2012.