Pressure Transient Analysis for High-Permeability Reservoirs

Field experience has shown that pressure data measured in extremely high permeability reservoirs (kh ~ 10⁶md-ft) are affected by wellbore effects such as storage, temperature changes, reservoir pres sure trend and noise in pressure measurements. These effects are particularly important in light of the small pressure response observed during a well test. The present work presents methods to analyze pressure drawdown and buildup tests performed under the influence of unknown linear reservoir pressure trend (m*). For a drawdown test a graph of t dp_wf/dt vs t yields a straight line of slope m* and intercept m (semilog slope); for a buildup test a graph of dp_ws/dt vs t_p/∆t(t_p+∆t) gives a straight line of slope m and intercept m*. Field cases are presented to illustrate the application of this method and the effects of different wellbore phenomena; both surface shut-in and bottomhole shut-in examples are included.