Laboratory evaluation of distributed coaxial cable temperature sensors for application in CO₂ sequestration well characterization

Abstract

Downhole monitoring plays a crucial part in a geological carbon dioxide (CO2) sequestration project, especially in providing early warnings of failure. However, most downhole monitoring technologies are often low in spatial resolution and time‐consuming, or expensive and have system longevity issues. To address this issue, a robust and cost‐effective distributed coaxial cable Fabry‐Perot interferometer‐based temperature sensor is proposed for real‐time downhole monitoring. The coaxial cable sensor (CCS) was made in house and tested using a high pressure high temperature (HPHT) testing apparatus to study the sensor accuracy, sensitivity, stability, and crosstalk effect in simulated downhole conditions. The laboratory test results indicate that the sensor can work under simulated downhole conditions of pressures up to 1000 psia and temperatures up to 110°C. At 1 ATM, the sensor has an accuracy of about 1%. At 1000 psia, the hysteresis phenomenon is observed, but it is reduced and tends to stabilize after repeated heating and cooling treatments. The pressure crosstalk effect was observed on the flexible cable sensor and minimized on the rigid cable sensor. The temperature and pressure range of the distributed CCS allows long‐term in situ monitoring for a well depth up to 2500 feet, which would prove of great value in detecting temperature change associated with wellbore leakage that may lead to groundwater contamination. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Development and evaluation of the coaxial cable casing imager: a cost‐effective solution to real‐time downhole monitoring for CO2 sequestration wellbore integrity

“…In addition, the coaxial cable sensors are free of the threat of hydrogen darkening, which could be fatal to fiber‐optic sensors however. The temperature and pressure rating of the coaxial cable sensors (110°C and 1000 psi) would allow a downhole deployment of 2500 ft, and coaxial cables that use ceramic, silica, or other high temperature tolerant dielectrics could survive pressures of 10 000 psi and temperatures of 1000°C, promising the technology to be applicable for deeper downhole deployment.…”

“…And when the ambient temperature remains constant, the relative frequency shift of the interferogram equals the change of distance between the two reflectors, which is the strain measured along the sensor length. For more details on the coaxial cable sensor working mechanism, refer to Li et al …”

“…[26][27][28] The strain sensor has been tested to have a measurement accuracy of about 15 micro-strain, 29 and a recent study proved that the temperature sensor can perform with high accuracy under 110°C and 1000 psi. 30 Due to the low cost and high robustness of the coaxial cable sensors, and inspired by the SureView TM RTCM system, a permanent downhole casing imaging system based on coaxial cable Fabry-Perot interferometer (CCFPI) strain sensors is developed and evaluated as a solution to real-time downhole monitoring for CO 2 sequestration wellbore integrity in this paper. Figure 1(a) is the CCFPI strain sensor manufactured in house.…”

“…And when the ambient temperature remains constant, the relative frequency shift of the interferogram equals the change of distance between the two reflectors, which is the strain measured along the sensor length. For more details on the coaxial cable sensor working mechanism, refer to Li et al 30 Rambow et al 25 introduced the helical wrapping of fiber-optic sensors on the casing to increase the measurable casing axial strain for limited sensor measurement ability. For a helically wrapped cable at θ degree ( Fig.…”

Borehole Heat Budget Calculator: A New Tool for the Quick Exploitation of High-Resolution Temperature Profiles by Hydrogeologists

“…The development of techniques focusing on thermal logging is also remarkable in the field of geological CO 2 storage, where one of the largest concerns is the potential leak of the injected CO 2 from the storage reservoir [17]. Most recent technical developments in this field include permanent monitoring systems installed in injection and monitoring wells, like optical fiber DTS, Fiber Bragg Grating sensors and coaxial cable temperature sensors [18]. Analytical models for inferring CO 2 leakage from temperature logging data have also been recently published [19].…”