Downhole Fiber Optics Are Changing the Well's Footprint

Abstract

Guest editorial “Ephemeralization” is the term coined by engineer Buckminster Fuller, the father of the geodesic dome and an early environmental activist, to describe the advancement of technology that achieves “more and more with less and less until eventually you can do everything with nothing.” This idea of doing more with less is at the heart of advances in downhole fiber-optic technology, and, in relative terms, its application is not far removed from doing nearly everything with almost nothing. Using light-transmitting optical fibers slightly thicker than a human hair and similar to the technology that brings Internet capacity to your home, we have been measuring wellbore parameters such as temperature, pressure, strain, vibration, and sound (acoustics) for years. In the near future, with the development of new optical or photonic sensing methods for chemical, microdeformation, resistivity, magnetic field, and other monitoring solutions, the industry will be able to integrate, visualize, and analyze numerous operations and activities downhole in real time, thus extending the life of the well and the reservoir. More Photons, Fewer Electrons Fuller illustrated his concept of ephemeralization by comparing the tons of copper wire required for a trans-Atlantic communication cable that could be replaced with ounces of the copper wire that it takes for a single communications satellite. With fiber-optic cables, the comparison is equally dramatic in many ways. Legacy electronic systems require deployment of complex, dedicated downhole instruments with millions of transistor junctions to make discrete wellbore measurements at specific points and times. In marked contrast, fiber-optic technology uses low-cost, low signal loss, high-bandwidth, silica glass transmission lines down-hole in concert with surface optoelectronic instruments to continually acquire real-time, remote, fully distributed measurements over the entire length of the installation, making the solution highly scalable. Leaving instrumentation on the rig floor, and not within the wellbore, removes risk from the hostile environment and enhances operating parameters. For instance, fiber-optic sensing and monitoring have been used in environments of up to 300°C (572°F) for years with great success. Solutions exist today for much higher temperatures. In contrast, electronic solutions are limited to less than about 200°C (392°F) for permanent deployment. As the technology evolves, surface instrumentation can be upgraded and connected to the same downhole fiber-optic sensors, instantly providing better data and potentially new sensing applications. For example, instrumentation connected to fiber-optic cables originally deployed on pipelines for telemetry decades ago is now being used to monitor distributed flow, temperature, acoustics, and tubular strain across many kilometers, thus enabling leak detection, flow restriction identification, object tracking, and other capabilities.