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Journal of Canadian Petroleum Technology, Vol.40, No.12, 5-8, 2001
Retrograde condensate dropout phenomena in rich gas reservoirs - Impact on recoverable reserves, permeability, diagnosis, and stimulation techniques
Gas condensate reservoirs exhibiting classic "dew point" or retrograde condensate dropout behaviour exist in many areas in the world. These reservoirs are unique in that, as the reservoir pressure is decreased, a certain volume of the heavy end fraction of the gas is precipitated in liquid form from solution in the gas. This condensate liquid may be temporarily or permanently trapped in the reservoir, causing severe reductions in gas production rates and the permanent loss of a large portion of the volatile and valuable condensate liquids (due to capillary pressure-induced trapping effects in the porous media). This paper reviews the basic theory of gas condensate dropout and describes, in detail, damage problems that may be associated with production of reservoirs of this type. Techniques for mitigating condensate dropout problems on a production basis, as well as stimulation techniques such as repressurization, lean and rich gas injection, surfactant and solvent injection, in situ combustion and water/gas injection, are reviewed, and the advantages and disadvantages of the techniques discussed.