Sensa tube with fiber optic distributed temperature sensing (DTS) has provided useful real time information for Pemex in various wells through thermal analysis of distributed temperature data. Four case studies are presented in this paper: the first case corresponds to a water injection profile survey at a Northern project. The other cases are related to gas lift optimization in the Northern and Southern Mexican regions.
As a part of the Pemex operated secondary recovery project in a Northern field, Fiber Optic Distributed Temperature Sensing technology has been used to monitor the water injection and warm-back temperature profiles across two perforated and fractured intervals, revealing the preferential flow into a one interval. The DTS thermal analysis provided important information to Pemex, which used the results as a guideline to take corrective action to increase the efficiency of their secondary oil recovery project. Pressure transient data was also collected to aid in the interpretation of the system using memory pressure gauges run on the fiber optic Sensa tube.
The remaining case studies will demonstrate DTS gas lift systems optimization projects. One of these cases shows an example of an efficient gas lift system, meaning no need of post work-over well intervention. The other two case studies reveal issues with the gas lift system design, which compromised the lift efficiency and consequently the well productivity.
Data acquisition using a portable fiber-optic Sensa tube unit has provided important information in a cost effective way. The DTS measurement provides a real-time and continuous temperature profile of the entire well, enabling the operator to monitor simultaneously all the gas lift valves, which is not possible to achieve with the usual time-consuming PLT surveys. Ultimately, the DTS monitoring has proven to be an efficient and reliable tool, saving the operator well intervention time and allowing immediate rectification of the issues observed.