Fiber Optic Pressure Measurements Open Up New Experimental Possibilities in Hydrogeology

Abstract

Fiber-optic (FO) technology is being used increasingly for measurement methods in a variety of environmental applications. However, FO pressure transducers are rarely used in hydrogeological applications. We review the current state of Fabry-Pérot interferometry-based FO pressure transducers, including their advantages and limitations, as another option for high-resolution pressure-or head-change measurements in conventional or advanced aquifer testing. Resolution and precision specifications of FO transducers meet or exceed commonly used non-FO pressure transducers. Due to their design, FO transducers can be used in small-diameter (inner diameter ≥1/4 inch) and continuous multichannel tubing (CMT), sampling points, multilevel packer systems, and Direct Push-based in situ installations and testing. The small diameter of FO transducers provides logistical advantages-especially for tests with monitoring at many zones in a number of wells and/or CMTs (e.g., no reels, placement just below water level in access tubes vs. within isolated zones, reduced weight and volume, small footprint at single point of data acquisition). Principal limitations are small measurement drift that may become evident for tests longer than a few hours, and higher-than-average cost. We present field examples of FO transducer performance in short-term tests with high consistency of acquired data and higher resolution (i.e., capturing significant hydrologic information) compared with commonly used non-FO transducers. Given the above, including advantageous logistical features, FO transducers can open new experimental possibilities in areas of high-resolution three-dimensional (3D) heterogeneity (flow and transport, remediation, critical zones); 3D fracture networks and fundamental hydromechanical behavior; complex 3D flow and leak detection (mines, dams, repositories, geothermal systems).

Stiff, Smooth, and Solid? Complex Fracture Hydraulics' Imprint on Oscillatory Hydraulic Testing

“…Across all oscillation periods, the numerically simulated head amplitudes matched the analytical head amplitudes within 1 mm or less. This level of numerical modeling error cannot be differentiated from data measurement error of commonly employed head change sensors (Leven & Barrash, 2022; Patterson & Cardiff, 2022).…”

The Two-Stage Suspension System of the Fiber Optic Vector Hydrophone for Isolating the Vibration from the Mooring Rope

“…A fiber optic sensor has the unique advantages of small size, high sensitivity, light weight, being immune to electromagnetic interference, and being easy to multiplex. Therefore, it has been widely used to measure various physical parameters of interest, such as pressure [ 1 , 2 , 3 , 4 , 5 ], temperature [ 4 , 5 , 6 , 7 , 8 , 9 ], salinity [ 7 , 10 , 11 ], as well as some kinematic parameters [ 12 , 13 , 14 , 15 , 16 ]. The fiber optic accelerometer, which takes the acceleration as the measurand, is one type of fiber optic sensor.…”

Replies to Comments on “Aquifer Characterization Using Fiber Bragg Grating Multi‐Level Monitoring System” by Leven and Barrash

“…Reply to comment 1: Leven and Barrash (2022) have presented the specifications (e.g., accuracy and resolution) of fiber optic pressure (FP) sensors they used in Table 2 of their work. The discussion of whether the resolution is a reasonable indicator is interesting, but out of the scope of our article (Wang et al 2022).…”