In typical drill-stem testing (DST), transient pressures are gathered downhole while rate measurements occur at the surface. Adverse effects of heat transfer upon pressure, particularly during a buildup test in a gas well necessitate the close proximity of pressure measurements to the point of fluid entry. While pressure measurements are reliable with sufficient resolution in most settings, rate measurements often lack synergy with pressure due to the sensor resolution and frequency of monitoring. This lack of pressure/rate harmony may precipitate significant uncertainty in transient-test interpretations.
This paper presents a case study for a deepwater asset in Western Australia, where temperatures were recorded at various depth stations in four wells, each in a different reservoir, before, during, and after transient testing, in addition to the traditional downhole pressure and surface rate measurements. This temperature data allowed estimation of gas flow rates. The flow rate accuracy increased at shallower depths because increased heat transfer enhanced the fidelity of measurements. Overall, the distributed temperature data allowed the estimation of both the static geothermal and the dynamic flow temperature gradients.