Understanding flow distribution across the well is significant piece of surveillance and important input for decisions related to well and reservoir management. Companies face significant challenges to monitor it. DTS is one of the technologies to mitigate challenges and minimize surveillance costs. As part of surveillance plan of ACG Res02 pilot program, DTS has been installed on a newly drilled gas injector (GI1). Significant learnings have been acquired from this trial.

GI1 was drilled as part of a pilot program on Res02 reservoir, which is currently at early stages of development. It has been equipped with number of surveillance tools as well as DTS across the whole sand interval. DTS profile on injector was generated based on difference in temperature of injected fluid and reservoir. Specifically in ACG environment injected gas temperature is higher than that of reservoir. Hence, warming effect was expected on the zones taking injected gas where due to heterogeneous nature of the reservoir, uneven injection into sublayers can occur.

DTS enabled real-time monitoring of how temperature profiles change across the sands and revealed uneven distribution of injected gas across the reservoir. When gas injection rate was increased, clear change in temperature profiles was observed – injection was getting into the lower sands as well. Moreover, shut-in DTS traces helped more accurately identify gas taking sands based on coolback effect. As injected gas temperature is higher than the reservoir temperature, temperature profile will be cooling back towards the geothermal gradient once the well is shut-in. This can be considered as warmback analogue that can be seen in water injector temperature logs.

Introducing DTS on gas injectors is both cost efficient and provides continuous flow monitoring, which enables real time decision making. Since it is dealing with only one fluid phase (gas) it provides more certainty. Information gathered from DTS will have a strong impact on field development planning, pressure maintenance, as well as smart completion designs.

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