Mitigation of the remote gauge problem in temperature transient analysis

The continuous stream of data from wells completed with multiple permanent, downhole sensors has created new monitoring possibilities. One new workflow, TTA (Temperature Transient Analysis) has proven to be particularly valuable for allocation of flow rates and phase cuts as well as for analysis of the properties of the near-wellbore formation. However, the measured temperature signal suffers considerable attenuation when the gauge is installed distant from the producing layer. This loss in signal quality has to be accounted for before carrying out TTA. This paper investigates the effect of heat transmission in the wellbore on TTA, evaluates existing transient thermal wellbore models and develops models to reconstruct the sandface temperature from the temperature measured by a gauge located at some distance from the sandface. The possibility of estimating the thermal properties of the wellbore and surrounding formation using these models is also studied. Two approaches are proposed for mitigating the remote gauge problem. The first approach reconstructs the sandface temperature from the degraded gauge temperature measurement data. Temperature reconstruction was found to be possible providing an accurate model of the wellbore is available. Both numerical, transient, thermal wellbore simulators and analytical thermal wellbore models may be used. Numerical inversion of the analytical transient thermal wellbore model is necessary since analytical inversion is impractical due to the result being very sensitivity to errors in measured gauge temperature. The second approach requires producing the well under conditions that minimize the attenuation. Empirical methods may be used to quantify the heat transfer effect, when conditions are such that the transient temperature signal is "good enough" for TTA. This approach also also allows estimating the degree of uncertainty (due to wellbore heat transfer) on the TTA. This work would extend the application of TTA to wells where analysis was previously impossible because the gauge was installed distant from the producing layer. This extension of TTA further increases the value-added by installing permanent downhole gauges.