WATER AND HYDROCARBON PHASE TRAPPING IN POROUS-MEDIA - DIAGNOSIS, PREVENTION AND TREATMENT

The entrapment of extraneous phases within porous media can occur in a number of different situations during drilling, completion, workover and production operations. The introduction of an additional immiscibl e phase, or an increase in an existing phase saturation within porous media can cause deleterious relative permeability effects which can su bstantially impact the permeability and relative permeability to oil o r gas. This phenomenon is commonly described as aqueous phase trapping or hydrocarbon phase trapping, depending on the situation under consi deration. This paper describes specific conditions required for the es tablishment of aqueous and hydrocarbon phase traps and provides diagno stic equations to evaluate the potential severity of an aqueous phase trap in a given reservoir situation. Specific procedures are recommend ed for the prevention of aqueous phase traps during drilling, completi on and production operations and, in a situation where phase traps are determined to exist in a reservoir, a variety of treatment techniques are presented to attempt to remove or reduce the severity of the aque ous or hydrocarbon phase trapping phenomenon.