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Mitigating Freezing Problems During Winter Surface Measurement Testing

By R. Kelly | Thu, 22 Jan 2015

In winter months, performing DFIT or pre-frac, injection fall-off testing using surface measurements can present challenges attributed to below freezing temperatures.  We routinely see erratic pressure responses in and around the wellhead when temperatures remain below freezing for a sustained period of time (>12 hours). Recognizing the problems associated to frozen wellheads and implementing a plan that would allow preservation of the collected data set is important and deserving of consideration.

The pictures shown below reveal a completely frozen needle (Fig. 1) valve along with the fluid internal to it. The erratic nature of the data set (Fig. 2), and gauges that arenít tracking pressure, and departure from the expected fall-off slope all contribute to the estimation that this is an event where freezing has occurred. This was indeed confirmed upon retrieval of the gauges that were connected to a frozen needle valve. The subsequent plot showing erratic pressure response provides evidence of the problems that wellhead freezing effects can have on collected data that will ultimately be inaccurate.

Figure 1 

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Figure 2 

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Summary

Winter freezing effects are easily mitigated by installing thermal blankets such as an electric blanket around the wellhead and wing valve where gauges are connected, or placing a heater/blower in the general area of the wellhead, ensuring however that hot air is not directly blowing onto the gauge itself. Other methods can be implemented to keep temperatures around the wellhead above freezing and will help to ensure data quality and the ability to analyze the set.



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