Rock massif temperature changes measurement with regard to thermal responses generated by a thermal response test device

Látal, Jan; Vitasek, Jan; Koudelka, Petr; Šiška, Petr; Liner, Andrej; Pápeš, Martin; Witas, Karel; Hejduk, Stanislav; Vašinek, Vladimír

doi:10.1117/12.2017241

Cited by 6 publications

(1 citation statement)

References 7 publications

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“…As mentioned at the beginning of the article, we have used the DTS system to measure temperature changes of the rock mass through measured thermal boreholes in a polygon [36][37][38]. The technology of the DTS system is based on the principle of optical reflectometer, i.e., a light impulse, at wavelength of 975 nm, 1064 nm or 1550 nm according to the type of DTS and width of 10 ns, is released into the filament.…”

Section: Used Methods and Devices For Measurements And Temperature Logging Of Bhesmentioning

confidence: 99%

Inquiry into the Temperature Changes of Rock Massif Used in Energy Production in Relation to Season

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Látal

Grafova

et al. 2021

Sensors

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This research was undertaken to perform and evaluate the temperature measurement in the ground utilized as an energy source with the goal to determine whether significant temperature variations occur in the subsurface during the heating season. The research infrastructure situated on our University campus was used to assess any variations. The observations were made at the so called “Small Research Polygon” that consists of 8 monitoring boreholes (Borehole Heat Exchangers) situated around a borehole used as an energy source. During the heating season, a series of monthly measurements are made in the monitoring boreholes using a distributed temperature system (DTS). Raman back-scattered light is analysed using Optical Frequency Time Domain Reflectometry (OTDR). Our results indicate that no noticeable changes in temperature occur during the heating season. We have observed an influence of long-term variations of the atmospheric conditions up to the depth of a conventional BHE (≈100 m). The resulting uncertainty in related design input parameters (ground thermal conductivity) was evaluated by using a heat production simulation. Production data during one heating season at our research facilities were evaluated against the design of the system. It is possible to construct smaller geothermal installations with appropriate BHE design that will have a minimal impact on the temperature of the surrounding rock mass and the system performance.

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Section: Used Methods and Devices For Measurements And Temperature Logging Of Bhesmentioning

confidence: 99%

Inquiry into the Temperature Changes of Rock Massif Used in Energy Production in Relation to Season

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Látal

Grafova

et al. 2021

Sensors

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Optical fiber based distributed temperature systems deployment for measurement of boreholes temperature profiles in the rock massif

et al. 2016

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Well-scale demonstration of distributed pressure sensing using fiber-optic DAS and DTS

Ekechukwu¹,

Sharma²

2021

Sci Rep

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In this study, we used data from optical fiber-based Distributed Acoustic Sensor (DAS) and Distributed Temperature Sensor (DTS) to estimate pressure along the fiber. A machine learning workflow was developed and demonstrated using experimental datasets from gas–water flow tests conducted in a 5163-ft deep well instrumented with DAS, DTS, and four downhole pressure gauges. The workflow is successfully demonstrated on two experimental datasets, corresponding to different gas injection volumes, backpressure, injection methods, and water circulation rates. The workflow utilizes the random forest algorithm and involves a two-step process for distributed pressure prediction. In the first step, single-depth predictive modeling is performed to explore the underlying relationship between the DAS (in seven different frequency bands), DTS, and the gauge pressures at the four downhole locations. The single-depth analysis showed that the low-frequency components (< 2 Hz) of the DAS data, when combined with DTS, consistently demonstrate a superior capability in predicting pressure as compared to the higher frequency bands for both the datasets achieving an average coefficient of determination (or R2) of 0.96. This can be explained by the unique characteristic of low-frequency DAS which is sensitive to both the strain and temperature perturbations. In the second step, the DTS and the low-frequency DAS data from two gauge locations were used to predict pressures at different depths. The distributed pressure modeling achieved an average R2 of 0.95 and an average root mean squared error (RMSE) of 24 psi for the two datasets across the depths analyzed, demonstrating the distributed pressure measurement capability using the proposed workflow. A majority of the current DAS applications rely on the higher frequency components. This study presents a novel application of the low-frequency DAS combined with DTS for distributed pressure measurement.

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Rock massif temperature changes measurement with regard to thermal responses generated by a thermal response test device

Cited by 6 publications

References 7 publications

Inquiry into the Temperature Changes of Rock Massif Used in Energy Production in Relation to Season

Inquiry into the Temperature Changes of Rock Massif Used in Energy Production in Relation to Season

Optical fiber based distributed temperature systems deployment for measurement of boreholes temperature profiles in the rock massif

Well-scale demonstration of distributed pressure sensing using fiber-optic DAS and DTS

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