An openhole drillstem test (DST) simulates producing conditions to help operators determine if a formation may be commercially productive during the drilling phase of the well. A DST isolates a formation with packers, and a tester valve opens to expose the formation to lower hydrostatic, which causes the formation to produce. After a predetermined flow period, a downhole shut-in valve closes to start a buildup period. The sequence of flow and closed-in periods is repeated as required.

Testing can provide information such as effective perme-ability, skin damage, formation pressure, flow rate, fluid type, and radius of investigation. Effective permeability, skin damage, and formation pressure calculations are possible only if the buildup period is long enough to reach Horner data.1  The duration of close-in periods is generally based on rule of thumb, bubble-hose response, or field experience. Surveys of current DST reports indicate that 30% of formations tested were not shut in long enough for Horner data to be obtained. The best method to determine the length of flow and shut-in periods is to monitor the pressures real-time at the surface. Wireline surface readout is available but is costly and poses risks, since the wireline is in the well. This paper discusses the operation and application of a new wireless telemetry tool that transmits real-time pressure and temperature readings to surface on an openhole DST.

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