Db. Bennion et al., Remediation of water and hydrocarbon phase trapping problems in low permeability gas reservoirs, J CAN PET T, 38(8), 1999, pp. 39-48
Aqueous and hydrocarbon phase traps can occur in porous media when water- o
r oil-based fluids come into contact with a formation which exhibits a "sub
irreducible" initial liquid saturation of the phase of interest. This commo
nly occurs with water-based fluids in many low permeability desiccated gas
bearing formations and in depleted conditions in rich gas retrograde conden
sate; reservoirs. This paper documents how phase traps are induced by direc
t displacement, countercurrent imbibition or depletion effects, and present
s techniques for diagnosing whether a reservoir is B candidate for an aqueo
us phase trapping problem. Techniques to minimize problems with aqueous and
hydrocarbon phase trapping are reviewed, followed by discussion of methods
to reduce or remove the effect of existing phase traps, such as increased
drawdown, alteration of IFT, alteration of pore geometry or direct removal
methods. A brief discussion of laboratory techniques used to screen the opt
imum process for selection are also presented.