Downhole Sand-Ingress Detection With Fiber-Optic Distributed Acoustic Sensors

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 183329, “Downhole Sand-Ingress Detection With Fiber-Optic Distributed Acoustic Sensors,” by Pradyumna Thiruvenkatanathan, Tommy Langnes, Paul Beaumont, Daniel White, and Michael Webster, BP, prepared for the 2016 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 7–10 November. The paper has not been peer reviewed. There is currently no proven technology available in the market that accurately identifies downhole sand-ingress locations in real time. In this paper, the authors present results from use of a new technology that uses in-well-conveyed fiber-optic distributed acoustic sensing (DAS) for the detection of sand-ingress zones across the reservoir section throughout the production period in real time. Introduction Mechanical sand-control systems are not always fully effective. The end result may be high sand production, which results in choking back the well and reducing hydrocarbon production significantly. In most cases, the precise sanding interval is unknown, making sand-remediation operations (such as remedial plug placements) often ineffective. A successful remediation requires identification of locations of sand entry to inform targeted sand-shutoff operations. However, no proven technology accurately identifies sand-ingress locations during well production in real time. The technology described in this paper has now been used successfully To monitor sand ingress during production (in real time) to inform and optimize oil production To inform and implement a targeted sand-shutoff operation to increase hydrocarbon-production rates To assess the reliability of the sand-control equipment during production to improve future designs Sand Detection While conventional surface acoustic sand detectors provide a delayed indication of onset of downhole sanding events, they do not provide information about the zones in the reservoir that are producing sand. A successful sand-shutoff operation, however, requires knowledge and definitive identification of the zones (or depth sections) in the reservoir contributing to sanding and their relative concentrations. DAS has been viewed as a potential candidate technology for downhole sand detection in recent years. DAS systems are intrinsic optical-fiber-based acoustic-sensing systems that use the backscatter component of the light injected into an optical fiber to detect acoustic perturbations along the length of the fiber. The fiber itself acts as the sensing element, with no additional transducers in the optical path, and measurements are taken along the length of the entire fiber, allowing for a true distributed measurement using a single fiber. The technology provides sensitivity to strain variations by monitoring changes in the length and index of refraction of the fiber induced by impinging acoustic pressure waves.