Experimental study of effect of CO2 injection on rocks: coupling hydrodynamic, mechanical and geochemical processes

Programa Oficial de Doutoramento en Enxeñaría Civil . 5011V01[Resumo] Este traballo nace amparado na necesidade de buscar novas solución ó aumento de emisións de gases nocivos para o medio ambiente. O almacenamento xeolóxico de CO2 é a etapa final do proceso de captura, transporte e almacenamento de CO2, consistente en inxectar CO2 nunha formación xeolóxica profunda. Dita inxección garda relación coa preocupación do papel que os gases de efecto invernadoiro poden ter sobre o clima. O obxectivo fundamental radica en obter información sobre o comportamento hidromecánico e xeoquímico das rocas a través do seguimento simultáneo de parámetros relevantes (deformacións, variacións na permeabilidade, indicadores xeofísicos, etc.). Considéranse os seguintes fitos: a) Deseño, definición e posta en marcha do sistema experimental b) Obtención de resultados c) Interpretación cualitativa e cuantitativa dos resultados O dispositivo experimental utilizado sobre o que se constrúe o ensaio de inxección é a cela triaxial, con pratos deseñados para a aplicación de presión de poro e propagación de ondas. Adicionalmente realizouse o estudo de análises de frecuencias de ondas P, S1 e S2, así como unha batería de ensaios xeomecánicos (triaxiais, compresión simple e tracción directa e indirecta) co obxectivo de caracterizar o material previamente a ser ensaiado.[Resumen] Este trabajo nace amparado en la necesidad de buscar soluciones al incremento de emisiones de gases nocivos para el medio ambiente. El almacenamiento geológico de CO2 es la etapa final del proceso de captura, transporte y almacenamiento de CO2, consistente en inyectar CO2 en una formación geológica profunda. Dicha inyección guarda relación con la preocupación del papel que los gases de efecto invernadero pueden tener sobre el clima. El objetivo fundamental radica en obtener información sobre el comportamiento hidromecánico y geoquímico de las rocas a través del seguimiento simultáneo de parámetros relevantes (deformaciones, variaciones en permeabilidad, indicadores geofísicos, etc.) Se tienen en consideración los siguientes hitos: a) Diseño, definición y puesta en marcha del sistema experimental. b) Obtención de resultados. c) Interpretación cualitativa y cuantitativa de los resultados El dispositivo experimental utilizado sobre el que construye el ensayo de inyección es la celda triaxial, con platos diseñados para la aplicación de presión de poro y propagación de ondas. Adicionalmente se realizó el estudio de análisis frecuencias de ondas P, S1 y S2, así como una batería de ensayos geomecánicos (triaxiales, comprensión simple y tracción directa e indirecta) con el objetivo de caracterizar el material previamente a ser ensayado.[Abstract] This research work has its origins on the need to find solutions to increased emissions of harmful gases to the environment. CO2 storage is the final stage of capture, transport and storage of CO2 process. This process involves the injection of CO2 in deep geological formations. That injection is directly related to the concern that greenhouse gases would have on climate. The main objective is obtaining information about hydromecanic and geochemical behaviour of rocks through the simultaneous monitoring of relevant parameters (deformation, permeability variations, geophysical indicators, etc.). The following milestones are taken into consideration: a) Design, definition and implementation of the experimental system. b) Obtainment of results. c) Qualitative and quantitative interpretation of results The experimental device used on building the injection test is the triaxial cell, with plates designed for the application of pore pressure and wave propagation. Additionally a frequency analysis study for P, S1 and S2 waves was performed, as well as a set of geomechanical tests (triaxial, simple compression, direct and indirect traction). These tests were performed in order to characterize the material before being tested

Hydrostatic, strike-slip and normal stress true triaxial hydrofracturing testing of Blanco Mera Granite: breakdown pressure and tensile strength assessment

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract:] We have designed and built a versatile testing device to perform hydraulic fracturing experiments under true triaxial conditions. The device, based on a stiff biaxial frame that can be installed in a servocontrolled press, can accommodate cube rock samples of up to 150 mm-edge. Using a low-permeability rock known as Blanco Mera granite, we have performed a series of tests across a range of confining pressures including hydrostatic, normal, and strike-slip regimes. We have verified the applicability of two simple fracture mechanics-based models for the interpretation of experimental results, and we have determined the value of tensile strength of the rock from the injection curves recorded. The orientation of the hydraulically-triggered fractures with respect to the applied stress has also been analyzed. Although the models proposed by Rummel and Abou-Sayed provided reasonably satisfactory results, especially for hydrostatic and strike-slip tests, the presence of heterogeneities and defects in the rock matrix may have a strong influence on the fracture behavior and, therefore, affect the interpretation of hydrofracturing tests.This work was funded by REPSOL S.A. and the support of the Spanish Ministry of Science and Innovation (PID2021-126419NB-I00). A. Muñoz-Ibáñez also acknowledges the Margarita Salas grant from the Spanish Ministry of Universities, funded by the European Union – Next Generation EU. Funding for open access charge: Universidade da Coruña/CISUG

Hydrofracturing tests on granite samples using a true triaxial device equipped with acoustic emission sensors

[Abstract:] We present a series of tests performed on granite samples using a true triaxial device designed and built at the Rock Mechanics Laboratory (University of A Coruña). The experiments were performed using cubic rock samples of 150 mm-edge, which were loaded to different stress conditions (σh < σh < σy < 45 MPa) on each loading axis. The device is based on a stiff steel frame that can be coupled to a servo-hydraulic testing machine that provides de vertical stress (av), while two high-pressure pumps are used to deliver the lateral stress (σh and ah). An additional high-pressure pump is used to inject the fluid (mineral oil) into the rock sample at a low constant-flow rate. The aluminium loading platens, which are bevelled at the edges to avoid interaction among adjacent faces, have holes and grooves to introduce acoustic emission sensors that allow the location of fracture propagation. The specimens were drilled using a 6 mm drill bit until reaching the geometrical centre. Then, a 1/8" (~3.18 mm) stainless steel tube is glued to the samples with epoxy. Strain measurements during the experiments were conducted using four strain gages attached to the orthogonal faces of the specimens. The system was further equipped with three LVDTs to account for the bulk displacement on each axis. Our results suggest a linear relationship between the breakdown pressure and the confining stress under hydrostatic conditions but no clear correlation in non-hydrostatic stress regime.Ministerio de Asuntos Económicos y Transformación Digital, MINECO; BIA2017- 87066-

Hubs and clusters approach to unlock the development of carbon capture and storage – Case study in Spain

Many countries have assigned an indispensable role for carbon capture and storage (CCS) in their national climate change mitigation pathways. However, CCS deployment has stalled in most countries with only limited commercial projects realised mainly in hydrocarbon-rich countries for enhanced oil recovery. If the Paris Agreement is to be met, then this progress must be replicated widely, including hydrocarbon-limited countries. In this study, we present a novel source-to-sink assessment methodology based on a hubs and clusters approach to identify favourable regions for CCS deployment and attract renewed public and political interest in viable deployment pathways. Here, we apply this methodology to Spain, where fifteen emission hubs from both the power and the hard-to-abate industrial sectors are identified as potential CO2 sources. A priority storage structure and two reserves for each hub are selected based on screening and ranking processes using a multi-criteria decision-making method. The priority source-to-sink clusters are identified indicating four potential development regions, with the North-Western and North-Eastern Spain recognised as priority regions due to resilience provided by different types of CO2 sources and geological structures. Up to 68.7 Mt CO2 per year, comprising around 21% of Spanish emissions can be connected to clusters linked to feasible storage. CCS, especially in the hard-to-abate sector, and in combination with other low-carbon energies (e.g., blue hydrogen and bioenergy), remains a significant and unavoidable contributor to the Paris Agreement's mid-century net-zero target. This study shows that the hubs and clusters approach can facilitate CCS deployment in Spain and other hydrocarbon-limited countries