The numerical borehole simulator HEX-B has been developed with the specific aim to
calculate the injectivity and productivity of open hole sections in deep wells. The
calculation requires the monitoring of wellhead data, such as the history of
salinity, flow rate, temperature and pressure but also the geometrical situation of
the borehole (casing diameter, cementation, ...). After different phases of
development HEX-S is now also suited to forecast downhole pressure data. 
As such, the transient pressure profiles during stimulation of wells GPK2 (June 2000)
and GPK3 (May 2003) were calculated based on measured wellhead data. A comparison of
the time-history of near-borehole events during the GPK2 test and downhole pressure
development in the open-hole sections of this borehole indicated that use of a heavy
(or dense) brine helped stimulate the bottom part of the well. The corresponding
analysis for the GPK3 test showed that the failure pressure of the fractures in the
bottom part of the wellbore was never exceeded when injecting the heavy brine.

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