In the last few years and in the context of a sequence projects of this type awarded to the team, a methdology has been established for the development of numerical tools based on the FEM, for the multiscale simulation of the behavior of concrete and other heterogeneous quasi-brittle materials subject to mechanical and environmental conditions, including the corresponding THMC coupling effects. The main features of the approach developed are: the explicit representation of the material meso-structure by means of numerically generated geometries based on volume fraction and shape of the particles, and the systematic use of zero-thickness interface elements with fracturebased constitutive laws in order to represent the initiation/evolution of cracks and interfaces, the role of which is often ucial role in the behavior of this type of materials. In the present proposal, which is based on the same methodology, it is proposed to develop a theoretical/numerical and experimental study of the acid attack by carbon dioxide on the portland cement used in the sealing of abandoned oil wells in the contex of geological CO2 storage. CO2 sequestration and storage is becoming nowadays an important part of the international effort to mitigate global warming. Large scale carbon dioxide storage plays a crucial role in the global strategy for greenhouse gas reduction. The use of abandoned oil and gas reservoir sites to for this purpose is a relatively recent practice and therefore the long term evolution of the system (reservoir+abandoned sealed wells+carbon dioxide) is not kown. One of the most critical aspects is the safety evaluation of abandond oil wells which were sealed with Hardened Cement Paste (PCH). The coupled model to be developed during the project would allow us to simulate the long term behavior of the cement well plugs subject to acid attack, with the subsequent evaluation of the carbon dioxide leakage risk. Specific objectives of the project are: a) Development of a model and numerical tools for the chemical and no-linear diffusion and transport analysis of [CO2], [Ca++] concentrations. Mechanicasl constitutive models with degradation of their properties depending on the changes in solid components of the ccement, and staggered coupling to the reactive transport model. General improvement and development of the computational tools. b) Experimental tests to evaluate the penetration of the degradation front in the cement paste exposed to the CO2 solution, and also to evaluate the mechanical properties (such as elastic modulus, tensile strength or fracture energy) of the CO2 degraded cement paste. c) Application studies of the downhole cement well plugs under realistic thermal, pore pressure and stress conditions, subject to CO2 acid attack. Parametric study of the resulting cement degradation and cracking, and the subsequent potential leaking of CO2. d) Continuation of on-going numerical and experimental studies at meso-scale level of concretes subject to expansive effects caused by alkali-silica reaction (ASR) external sulfate attack and high temperatures, which have been the main subject of study in previous funded projects.
Plan Estatal de Investigación Científica y Técnica y de Innovación 2013-2016
Programa Estatal de I+D+i Orientada a los Retos de la Sociedad
Retos de Investigación: Proyectos de I+D+i
Gobierno De España. Ministerio De Economía Y Competitividad, Mineco