Improved Monitoring System for Heavy Oil SAGD Wells

Abstract

This paper provides an overview of the development of fiber optic sensing for SAGD applications including a review of more than 10 years of work in development and field applications in Western Canada. Development of a fiber optic monitoring system to withstand the harsh environments experienced in the SAGD application requires consideration of the materials used to protect the downhole optical fiber, the chemistry of the downhole optical fiber, the basic optical fiber sensing technology implemented, and the optical interrogator functionality. Aspects covering corrosion of materials, hydrogen darkening, and system performance for different monitoring applications will be explored. Design and technical information will be provided along with certain case histories providing the applications and use of downhole fiber optics sensing for the SAGD applications including steamflood monitoring, sub-cool monitoring, and well integrity monitoring. Dealing with a harsh environment experienced downhole in the Western Canada SAGD applications including temperatures exceeding 230° C in high hydrogen environments has meant that the fiber optic sensing technologies have had to adapt and improve to be suitable to function reliably. Various technologies have been implemented throughout the previous 10 to 15 years, from Raman scattering based DTS systems to highly multiplexed Bragg grating based thermal monitoring systems. Multiple optical PT gauges have been designed and implemented. These include Fabry-Perot based systems as well as the Bragg grating based PT gauges. This paper will provide much-needed information to practicing engineers in the field of downhole reservoir monitor introducing them to concepts such as multi-point fiber Bragg grating based thermal monitoring and reliability of the monitoring systems. Information provided in this paper is applicable beyond the SAGD applications. The fiber optic monitoring systems may also be used for intelligent wells, subsea wells, and unconventional wells.