This paper describes the use of a Downhole Temperature Sensor Array, during a commingled Drill Stem Test, to accurately determine the density of the produced fluids. In a typical Drill Stem Test, using only downhole pressure gauges, any fluid contacts between the pressure gauges would be missed and the produced fluid density calculated would be erroneous.
Accurate calculation of the produced fluid densities is of great importance to the reservoir engineer since it forms a critical component of the equations of state used in the modelling of the reservoir. The main purpose of this paper is to show that knowledge of the produced fluid densities from each of the perforated intervals provides a more robust calculation of the zonal flowrate contributions using conservation of mass principles.
In this case study, the well was produced across three intervals with the deepest perforated interval producing a fluid with a higher density than the shallower perforated intervals. The higher density of the produced fluid from this deeper interval caused the wellbore fluids to slug during the flow periods with a measureable response in the pressure and temperature data. If this difference in the fluid properties is not taken into account then the zonal allocation flowrate will be in error since it relies on the density and specific heat capacity. Qualitative assessment of the temperature array data identified the producing zones and clearly highlighted the different fluid interfaces in detail that would remain hidden if relying solely on the pressure gauges.
This method is enabled by the deployment of a Downhole Temperature Sensor Array consisting of an array of discrete electronic temperature sensors alongside the TCP guns, generating continuous thermal profiles across the three intervals. This is augmented by a wireless data system of pressure points. All the data is collected real time throughout the entire Drill Stem Test.