Keywords: X-ray, sensor, oil, gas
Summary:After an oil or natural gas well is drilled, the integrity of the well must be maintained throughout its lifetime to ensure that no hydrocarbons leak into the environment. At the end of the well’s useful life, it must be plugged and abandoned (P&A) by completely sealing off the well from the surface and the surrounding rock. Prior to the Macondo accident and oil spill in 2010, ensuring that wells were properly plugged was not a priority as regulations were vague and not strictly enforced with the result that many abandoned wells today are leaking. Now, regulators have tightened P&A rules and the requirements for proving integrity. Consequently, the cost of P&A for oil companies has increased dramatically, so the industry has invested in technologies that enable cost effective P&A to ensure wells are properly sealed and will not leak in the future. This paper describes a novel method to probe an oil or gas well with X-rays to directly assess the well’s integrity in a more cost-effective and accurate manner than possible with current diagnostic methods. The downhole X-ray system relies on three key technologies: an inherently safe, electronic X-ray tube, novel photon-counting X-ray detectors, and high voltage generators. While these technologies are known outside the oil industry, adapting them to operate at high temperatures (up to 125°C or more) within the geometrical constraints of a borehole (< 5” diameter) was challenging. The resulting well logging tool surveys well integrity.