Do not believe those calculated bottomhole pressures

Large systematic errors exist both in the magnitude and trends of the Keck correlation,(1) when it is scaled up from laboratory results to field appli cations. Data also show an unexpected transient effect in most wells, where by changes in surface pressure of 100's to 1000's of psi are found to chang e the bottomhole pressure by only 10's or 100's of psi, respectively. The a uthors speculate on possible causes for this phenomenon, but conclude that additional work is needed for accurate predictions of bottomhole pressures during fracturing treatments.