Real-Time Fiber-Optic Casing Imager for Continuous High-Resolution Casing Monitoring

Abstract

This article, written by Assistant Technology Editor Karen Bybee, contains highlights of paper SPE 109941, "Real- Time Fiber-Optic Casing Imager," by M. Appel, SPE, D. Dria, SPE, J. Freeman, F. Rambow, SPE, and M. Shuck, SPE, Shell Intl. E&P, and B. Childers, S. Poland, SPE, and T. Dominique, Baker Hughes, prepared for the 2007 SPE Annual Technical Conference and Exhibition, Anaheim, California, 11-14 November. The paper has not been peer reviewed. During the last few years, significant progress has been made in the use of fiber-optic technology for well and reservoir surveillance. The full-length paper details recent advances in development of a real-time fiber-optic-based casing imager that is designed for continuous, high-resolution monitoring of tubular shape and enables determination of strain imposed on the tubulars. Small-scale and full-casing-size laboratory tests have demonstrated that the latest generation of this system is sufficiently sensitive to detect casing deformations of less than 10°/100 ft and covers compressive and tensile axial-strain ranges from less than 0.1 to 10%. Introduction In many regions of the world, regular monitoring of casing deformation needs to be an essential part of the reservoir-surveillance program because reservoir compaction and other geological conditions can impart significant loads on casing, which can lead ultimately to loss of the well. By monitoring the shape of the casing or the strain imposed on the casing, data may be available at a sufficiently early stage to enable remedial actions to prevent casing damage. Continuously monitoring casing deformation in real time improves the understanding of compaction and other strain-related reservoir conditions, which is essential for optimizing production and reserves recovery. Subsurface compaction and stress-change behavior can be investigated remotely by use of several indirect-measurement techniques. On land, subsidence monitoring in combination with microseismic detection, supported by tiltmeters and data derived from global-positioning systems, has been used to characterize reservoir compaction. Microseismic, seafloor pressure gauges, and seafloor tiltmeters give indications of changes occurring on the seafloor and subsurface. More recently, reservoir changes have been analysed using time-lapse-seismic techniques. Real-Time Casing Imager (RTCI) Considering the limitations of traditional in-well monitoring, a measurement technique was developed to measure real-time distributed strain and temperature along a well tubular with a very high spatial resolution. The technology is called RTCI and is based on fiber-optic technology. The main components of the RTCI include the following.A sensing fiber-optic cable attached to downhole equipment.A fiber-optic lead-in cable that would be run in the well with the downhole equipment and enables sending laser light to the sensing element of the fiber-optic cable.A surface interrogation unit designed to provide the laser light and to analyze detected signals.