CuuLong Joint Operating Company, Vietnam operates a number of HPHT and basement fractured reservoirs and has installed over 60 quartz or fiber optic permanent downhole gauges in development wells, since 2003. This paper reviews the selection process for the different type of gauges, gauge reliability and also details some of the considerations when assessing the relative cost advantage of each gauge type.

Equipment and material reliability has always been critical to success in the HPHT and fractured basement environment. As development wells target ever more challenging reservoirs, extreme testing and qualification processes are required to give reliable downhole sensors. This paper describes a methodology used by an Operator to address the significant challenges of selecting gauges for high temperature reservoir monitoring. The work details how the extensive qualification/testing process was successfully applied to select suitable gauges. Initially, after selecting quartz gauges the first deployment of an optical gauge system took place offshore Vietnam in February 2009. To date a total of 20 fiber optic gauges have been installed on different platforms in various reservoirs and when successfully installed have achieved a 100% success rate.

Four major areas were addressed using this methodology, which are necessary in order to ensure success:

  1. Establish applicable standards appropriate optical sensing technology to which components should comply, in order to qualify for selection.

  2. Determining the reliability of electronic gauge systems in the specified high temperature reservoirs environment.

  3. Develop an effective monitoring and optimization process that considers all possible scenarios, in order to properly assess the cost-benefit of the proposed system.

  4. Continually review and improve the system based on available data and analyses.

Application of this methodology has led to a 100% success rate for recently installed gauges and application of this system, developed over the past 10 years, should help other operators world-wide achieve similar success rates in comparable, 'extreme' reservoir monitoring environments.

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