Perforation Inflow Distribution Diagnostic (#PID) #welltests can differentiate inflow ratios in multi-layer completions. By perforating subsequently better layers, an increase in surface pressure buildup slope is equal to an increase in gas inflow. It may be necessary to blow down the wellbore to maintain critical flow conditions across the perforations. Analytical results are analogues to production logging surveys and can be utilized for identifying movable gas, proving recoverable reserves, determining log cut-off values, or identifying bypassed pay as well as non-performing layers.
Closed-chamber tests have been utilized for many years as an alternative to drill stem tests. The technique is transferable to several alternative welltest solutions.