Interpreting Transient Tests in High-Permeability, Gas-Condensate Reservoirs

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIn 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 gascondensate 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.

Decision Making With Uncertainty While Developing Multiple Gas/Condensate Reservoirs

“…10 schematically shows the reservoirs and wellbores in the material balance, wellbore, and network model. 7 There are nine "tank" material balance models feeding the network. Each tank had uncertainty distributions for the original gas-in-place and condensate-to-gas ratio provided by the subsurface team.…”

“…Details of transient testing 7 and completion options 8 are documented elsewhere. Table 1 presents the data used.…”