Stochastic fractured rock facies for groundwater flow modeling [Representación estocástica de facies de rocas fracturadas para la modelación del flujo de aguas subterráneas]

This paper presents simulation results of groundwater flow in fractured rocks. A stochastic approach is employed to build the conceptual model, a stochastic Equivalent Porous Medium fractured rock facies model, for the low-permeability bedrock found at Olkiluoto (Finland), which is the site chosen for the case-study. The volume of rock investigated is located around a cluster of boreholes and it covers an area of 160000 square meters. Field measurements during hydraulic interference tests are used to calibrate the groundwater flow model. Multiple stochastic facies realizations are considered to evaluate the impact of distribution and number of facies on simulated hydraulic heads and flow rates. This study quantifies the variability of numerical results, which is important for uncertainty analysis of hydrogeologic systems. Moreover, it shows that the stochastic facies conceptual model is a suitable alternative to discrete fracture network conceptual models

Deep geothermal resources in Quebec and in Colombia: An area that may develop based on French experience on geothermal power plants [Les ressources géothermiques profondes au Québec et en Colombie : un secteur don't le développement pourrait s'inspirer des centrales géothermiques en France]

Because of an increasing demand in electricity and a necessity of reducing greenhouse gas emissions, several countries envisage the development of the renewable energies. The geothermal energy is a particularly interesting alternative because it allows a production of electricity which is not influenced by weather conditions and it requires relatively restricted surface areas compared, for example, to the area required by a hydroelectric power plant. The literature review presented here summarizes the main characteristics of the geothermal potential in Quebec, in sedimentary basins, and in Colombia, in the area of the Nevado del Ruiz volcanic complex. Currently, in these two regions, the hydro-electric power dominates the electricity production, but there is a similar interest to the development of geothermal power plants. The French sites of Soultz-sous-Forêts in Alsace and Boiling in Guadeloupe are respectively presented as an example of exploitation of geothermal improved systems (Enhanced Geothermal System; EGS) and geothermal resources in volcanic regions. The first site constitutes a model for the future development of the deep geothermal exploitation in Quebec, whereas the second is an example for Colombia. A description of environmental impacts related to the exploitation of deep geothermal resources is presented at the end of this paper.Because of an increasing demand in electricity and a necessity of reducing greenhouse gas emissions, several countries envisage the development of the renewable energies. The geothermal energy is a particularly interesting alternative because it allows a production of electricity which is not influenced by weather conditions and it requires relatively restricted surface areas compared, for example, to the area required by a hydroelectric power plant. The literature review presented here summarizes the main characteristics of the geothermal potential in Quebec, in sedimentary basins, and in Colombia, in the area of the Nevado del Ruiz volcanic complex. Currently, in these two regions, the hydro-electric power dominates the electricity production, but there is a similar interest to the development of geothermal power plants. The French sites of Soultz-sous-Forêts in Alsace and Boiling in Guadeloupe are respectively presented as an example of exploitation of geothermal improved systems (Enhanced Geothermal System; EGS) and geothermal resources in volcanic regions. The first site constitutes a model for the future development of the deep geothermal exploitation in Quebec, whereas the second is an example for Colombia. A description of environmental impacts related to the exploitation of deep geothermal resources is presented at the end of this paper

Wood walls insulated with coconut fiber [Muro de madera aislado con fibra de coco]

Solid wood gives the shape to walls, while panels are the coating and they are nailed or screwed to the wood sections. In the cavities between the wood elements and the panels, a thermal and acoustic insulator must be added. Unfortunately, almost all of the currently used insulators (mineral wool, expanded polystyrene, polyurethane) are not biodegradable and require the use of vapor barriers (polyethylene sheets, aluminum foils, etc.) that deteriorate rapidly and that are relatively environmentally unfriendly. In this article, the use of coconut fiber instead of conventional insulators is suggested. The acoustic absorption and thermal conductivity coefficients of composite sections taken from wood walls with coconut fiber are estimated. In this way, good thermo-acoustic conditions inside the wood building are achieved using an ecological insulating material. © The author; licensee Universidad Nacional de Colombia

Geothermal energy in Colombia as of 2018 [Energía geotérmica en Colombia hasta 2018]

Colombia is a country with great potential for the exploitation of geothermal energy due to its high volcanic activity caused by the subduction between the Nazca and South American tectonic plates. However, this energy is yet to be exploited. This article seeks to describe, by means of a literature review and information processing, the current status of geothermal energy in Colombia, including the current regulations, the limitations, the recommendations to develop the geothermal energy, and some of the most important projects, studies, and research papers that have been emerged on the discovery, exploration, and exploitation of geothermal energy within the country, emphasizing the areas where exploration projects have been initiated, such as the Nevado del Ruiz volcano, the Tufiño Chiles Cerro Negro volcanic system, the Azufral volcano geothermal area, and the Paipa geothermal area. Over the years, energy vulnerability in Colombia and a government policy of fostering sustainable development in different territories have generated favorable conditions for the exploitation of geothermal resources. Nevertheless, there are several technical, infrastructural, legal, and institutional barriers that slow the proper development of these projects. © 2020, Pontificia Universidad Javeriana. All rights reserved

Fault characterization and heat-transfer modeling to the Northwest of Nevado del Ruiz Volcano

The Nevado del Ruiz Volcano is an area of great interest for future geothermal exploitation in Colombia facing exploration challenges as hydrothermal fluids originate deep into the fractured basement. Fieldwork conducted on the Northwest of this volcano confirmed the existence of fault zones and enabled collection of thirty rock samples from outcrops. Permeability of these samples was then measured in the laboratory with a steady-state gas permeameter, taking into account the Klinkenberg correction. The Porchet method allowed to obtain an estimation of in situ hydraulic conductivity in fault zones directly in the field. Thermal conductivity and heat capacity of the rock units were estimated from previous studies. 2D heat transfer and groundwater flow in porous fractured medium were simulated in the study area, using the free modeling package OpenGeoSys with data collected during fieldwork. Three modeling scenarios were considered, investigating the influence of fault dip in groundwater flow and heat transfer processes. It was possible to reproduce the temperature measured at the Hotel Termales hot spring, where the Samaná Sur fault appears to behave as a pathway for geothermal fluids. It was additionally found that fault dip has an influence on the simulated temperatures. When the dip is in favor of the fluid flow (90° facing fluid flow), the simulated surface temperature decreases. © 2018 Elsevier Lt

Enhanced geothermal systems: Review and analysis of case studies

This article reviews the characteristics of the EGS, sources of clean energy that promise to be an alternative to face the problems related to global warming caused by the use of fossil fuels like oil and natural gas. Currently in Colombia the geothermal systems of interest are hydrothermal, so there are no plans for the development of EGS yet, however, this article pretends to be an introduction to the reader interested in EGS and to be a reference to future projects developed in the national territory, describing the most significant places in the world where this technique has been used, along with its social perception and associated impacts. In addition, it seeks to analyze the differences between the hydraulic stimulation technique in the EGS and the fracking used for the extraction of shale gas. © 2020 Universidad Industrial de Santander

Geothermal potential assessment of the Nevado del Ruiz volcano based on rock thermal conductivity measurements and numerical modeling of heat transfer

This work presents an estimation of the geothermal potential of the Nevado del Ruiz (NDR) volcano, bridging the knowledge gap to develop geothermal energy in Colombia and improve resource estimates in South America. Field work, laboratory measurements, geological interpretations, 2D numerical modeling, and uncertainty analysis were conducted to the northwest of the NDR to assess temperature at depth and define thermal energy content. About 60 rock samples were collected at outcrops to measure thermal conductivity with a needle probe. A 2D numerical model, built from an inferred geological cross-section, was developed with the software OpenGeoSys to simulate the underground temperature distribution and then estimate the geothermal potential of a 1 km2 area with sufficient temperature, assuming a recovery factor equal to 2.4% and a 30 years exploitation time. Coupled groundwater flow and heat transfer were simulated in steady-state considering two different thermal conductivity scenarios. Results show that the average estimated potential is 1.5 × 10−2 MWt m−1 of the reservoir thickness, considering temperatures greater than 150 °C located at a depth of approximately 2 km, in a selected area situated outside of the Los Nevados National Natural Park (NNP), to avoid any direct intervention on this protected area. According to a Monte Carlo analysis considering pessimist and optimist scenarios of thermal conductivity, the estimated geothermal power was 1.54 × 10−2 MW m−1 (σ = 2.91 × 10−3 MW m−1) and 1.88 × 10−2 MW/m (σ = 2.91 × 10−3 MW m−1) for the two modeling scenario considered. © 2017 Elsevier Lt