6.4 Type Curves and Desuperposition

Type curves are also applicable to the analysis of buildup tests, though type curve matching techniques are not discussed fully in this section. Type curve matching provides a simple method for determining the time of start of transient flow during drawdown tests. A similar approach may be used to determine the time of start of semilog straight-line data in buildup tests with one additional step. Since a buildup is always preceded by a drawdown, the buildup data must be desuperposed before attempting a type curve match. It may be noted that desuperposition can also be performed on the second rate of a two-rate test. Early-time data obtained during a buildup may be desuperposed by assuming ?(P _wfp) to be constant at a value ?(P _wfo).