<title>Distributed temperature sensing (DTS) to characterize the performance of producing oil wells</title>

Abstract

This paper describes how distributed temperature sensing (DTS) based on Raman Scattering is being used as an in-situ logging technique in oil & gas wells. Traditional methods of gathering production data to characterize oil & gas well performance have relied on the introduction of electric logging tools into the well. This can be an expensive process in highly deviated or horizontal wells and usually results in the well being shut-in with the loss or deferment of hydrocarbon production. More recently permanently placed pressure sensors based on CMOS technology have been used, but these systems do not easily deliver distributed measurements and reliability has been found to be poor.In order to apply DTS technology to this new type of application a number of new processes and methods have been developed. These include improved optical fiber coatings for high temperature applications, adaptation of fiber-blowing techniques techniques pioneered by the telecoms industry for installation and advanced interpretation techniques that allow distributed temperature profiles in the oil & gas well to give valuable information about flowing profiles, fluid properties and the condition of artificial lift equipment that is used to enhance production.

Thermal, mechanical and chemical influences on the performance of optical fibres for distributed temperature sensing in a hot geothermal well

“…Furthermore, it has been observed that flushing the cable could significantly contribute to a reduction of harmful chemical species (e.g. hydrogen released from the cable itself due to cracking of forming oil at elevated temperatures Williams et al, 2000; along the cable and therefore increase the lifetime of the installation at high temperatures.…”

“…The ingression of hydrogen and the subsequent formation of hydroxyl causes strong absorption peaks at relevant wavelengths (Stone and Walrafen, 1982;Humbach et al, 1996;Williams et al, 2000). The increasing absorption at individual wavelengths leads to an increase in the differential attenuation between the Stokes and Anti-Stokes band.…”

“…Within the geothermal fluid of high temperature geothermal wells in Iceland, hydrogen is often present (Arnórsson, 1995). In the presence of hydrogen, however, optical properties of fibres degrade rapidly due to hydrogen ingression and hydroxyl formation (Smithpeter et al, 1999;Williams et al, 2000;Normann et al, 2001).…”

Fiber optic distributed temperature sensor mapping of a jet-mixing flow field

“…Both can be many kilometers long and have found use in measuring temperature within oil wells (Williams et al 2000) and along power cables serving offshore wind farms (Fromme et al 2011), as well as strain within infrastructure such as tunnels and pipelines (Rajeev et al 2013). Brillouin systems can achieve spatial resolution down to ~1 cm, while Raman is limited to ~1 m; time response is generally on the order of minutes (Bao and Chen 2012) though some commercial systems can now achieve data rates of approximately 1 Hz.…”

Technical Readiness and Gaps Analysis of Commercial Optical Materials and Measurement Systems for Advanced Small Modular Reactors

“…By far the more common type is the Raman backscattering reflectometer, which measures spontaneous Raman scattering (SRS). SRS is useful because the anti-Stokes Raman band is temperature-sensitive, and can be referenced against the comparatively insensitive Stokes Raman band (Williams et al 2000). A third type is a Brillouin backscattering reflectometer (Rogers 1999).…”