Over the past 3 years fiber optic slickline distributed temperature measurements (DTS) have become a commonplace method of monitoring Canada’s Deep Basin commingled gas wells produced through velocity string completions. The use of velocity string completions prohibits conventional production logging, so the wells are flowed up their annulus for a short period of time and a DTS slickline is used to monitor the flowing temperature profile. This temperature profile is then interpreted to give the flow from each reservoir zone. DTS is a much more cost effective solution than having to pull the tubing in order to run a conventional production log and allows testing of lower rate wells that would otherwise liquid load.

The analysis technique conventionally assumes that during the annular flow period, where the DTS is used to acquire the flowing temperature, all the thermal effects of the previous counter-flow production period have dissipated and the problem can be solved by an upward flow thermal model only. This paper evaluates the magnitude of the residual thermal effect of a period of counter-flow on the annular flow response over the timescales typical for DTS monitoring.

A counter-flow thermal model has been developed for typical well scenarios and the shut-in decay of the thermal response of this model is superposed on the conventional annular flow model to highlight the magnitude of influence of previous counter-flow production. The model is used to interpret the counter-flow response of annular flowing gas wells using real well DTS data and demonstrates the magnitude of the effect and how to use this method to improve the accuracy of the resulting flow analysis.

You can access this article if you purchase or spend a download.