In gas-condensate reservoirs, interpretation of static and dynamic skin is fraught with uncertainties when analysis is attempted with simple analytic tools. Problems compound when two-phase flow occurs owing to large drawdowns with flowing pressures dipping below the dewpoint pressure. Under this circumstance, static and dynamic skin values are difficult to separate using a single-phase analog.
This paper deals with issues surrounding transient-test interpretation when no discernible condensate bank forms in the well vicinity owing to low drawdown in high-kh reservoirs and low-condensate yields. In particular, we explore why skin values obtained by a single-phase analog cannot be mapped directly onto a two-phase numeric model.
Some of the key findings suggest that both components of skin are significantly lower when evaluated with a numeric model as opposed to its analytic counterpart. In gas-condensate systems, we recommend the use of a numeric model because of its superior ability to handle physics of flow. This is particularly so when long-term performance evaluation is sought.