Abstract
With the oil and gas industry growing rapidly, increasing the yield and profit require advances in technology for cost-effective production in key areas of reservoir exploration and in oil-well production-management. In this paper we review our group’s research into fiber Bragg gratings (FBGs) and their applications in the oil industry, especially in the well-logging field. FBG sensors used for seismic exploration in the oil and gas industry need to be capable of measuring multiple physical parameters such as temperature, pressure, and acoustic waves in a hostile environment. This application requires that the FBG sensors display high sensitivity over the broad vibration frequency range of 5 Hz to 2.5 kHz, which contains the important geological information. We report the incorporation of mechanical transducers in the FBG sensors to enable enhance the sensors’ amplitude and frequency response. Whenever the FBG sensors are working within a well, they must withstand high temperatures and high pressures, up to 175 °C and 40 Mpa or more. We use femtosecond laser side-illumination to ensure that the FBGs themselves have the high temperature resistance up to 1100 °C. Using FBG sensors combined with suitable metal transducers, we have experimentally realized high- temperature and pressure measurements up to 400 °C and 100 Mpa. We introduce a novel technology of ultrasonic imaging of seismic physical models using FBG sensors, which is superior to conventional seismic exploration methods. Compared with piezoelectric transducers, FBG ultrasonic sensors demonstrate superior sensitivity, more compact structure, improved spatial resolution, high stability and immunity to electromagnetic interference (EMI). In the last section, we present a case study of a well-logging field to demonstrate the utility of FBG sensors in the oil and gas industry.
Highlights
By 2017, according to forecasts, the world’s economies will demand about 33 million barrels per day [1,2,3,4,5,6,7,8,9,10,11,12,13,14]
Among optical fiber sensing methods, fiber Bragg grating (FBG) sensors, in particular, have attracted great interest because of their unique properties, which open up many opportunities for single-point sensing of many parameters in hard-to-reach spaces, with controllable cross-sensitivities and very compact size, making them suitable for embedded measurement
The FBG is the elastic element that experiences the strain force directly, acting as a mechanical spring. This configuration suffers from poor dynamic range and mechanical reliability since the FBG can only tolerate a maximum strain of about 1% (104 με)
Summary
By 2017, according to forecasts, the world’s economies will demand about 33 million barrels per day [1,2,3,4,5,6,7,8,9,10,11,12,13,14]. Among optical fiber sensing methods, fiber Bragg grating (FBG) sensors, in particular, have attracted great interest because of their unique properties, which open up many opportunities for single-point sensing of many parameters in hard-to-reach spaces, with controllable cross-sensitivities and very compact size, making them suitable for embedded measurement. These outstanding properties make FBGs especially well adapted for well-logging and seismic exploration in oil and gas fields. Our group’s fiber sensing instruments for measuring pressure and strain have been tested successfully in oil and gas fields, such as the Qingyang-Xianyang pipeline in 2006, the Liaohe oil field in 2011, the Changqing oil field in 2012 and by the China Petroleum Well-logging Company in 2015
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