This paper approaches the challenges of temporarily abandoned well monitoring with wet christmas tree (WCT), analyzes the regulatory requirements, the Brazilian scenario and proposes a new methodology system to checking the two Well Safety Barriers (WSB) integrity as required by the ANP (Petroleum National Agency, the regulatory institution in Brazil) resolution nO46/2016. So, the system is compared with other monitoring alternatives, even economically, namely: using rigs or plugging and abandonment. A system is presented that allow the monitoring by means of WCT chamber pressurization or depressurization, hydrocarbons detection, leak measuring by control valves, measuring the WTC chambers pressure, collecting the probable hydrocarbons in a safety way and, and if required, actuating some WTC valves. The control valves and WTC chambers are accessed by the Vertical Connection Module (VCM) mandrel where a modified abandonment cap will be installed with a Control Module on the top. An isolation valve is installed in the Control Module, as a WSB redundancy. The monitoring system avoids the use of expensive intervention rigs and allow the indefinite postponement of plugging and abandonment, entailing sensible economic gains. In addition, the control module installation is made along with the abandonment cap, therefore, no additional cost is required. Another main issue is that the control module monitoring not entails significative impact in the time of well inspection routine. Besides fulfills the legal requirement, the monitoring system provides safety in operations and economic gains when compared to other alternatives. The proposed system patent has been deposited in Brazil. The economy and safety offered by the monitoring system doesn´t have similarities to the existing methodologies in the international market. However, it will be necessary a test prototype to develop.

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