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In this paper, we present a general partition of unity-based cohesive zone model for fracture propagation and nucleation in saturated porous materials. We consider both two-dimensional isotropic and orthotropic media based on the general Biot theory. Fluid flow from the bulk formation into the fracture is accounted for. The fracture propagation is based on an average stress approach. This approach is adjusted to be directionally depended for orthotropic materials. The accuracy of the continuous part of the model is addressed by performing Mandel's problem for isotropic and orthotropic materials. The performance of the model is investigated with a propagating fracture in an orthotropic material and by considering fracture nucleation and propagation in an isotropic mixed-mode fracture problem. In the latter example we also investigated the influence of the bulk permeability on the numerical results.

New ways to decrease the level of CO2 in the atmosphere are necessary to reduce the effects of the global warmimg. Subsurface CO2 storage has been identified as one of the key methods to reduce the emissions of CO2. The most crucial requirements that must be fulfilled to obtain a license for CO2 storage are: safety, reliability and the ability to remediate unwanted leakage. Remediation or mitigation of unwanted migration from storage sites requires new approaches for which the feasibility is yet to be demonstrated. The remediation technologies are classified as passive (e.g. stop injection) or active (e.g. producing or removing CO2). If passive methods are not enough to permanently stop the leakage, they need to be coupled with active approaches. The methodologies that we present in this work were stringently risk based, to ensures that the obtained results can be adopted to improve and help the regulatory process: protocols, safety regulations and guidelines. We studied the feasibility of some promising active technologies: 1. inject a chemical mixture near the location of leakage that reacts with the CO2 or formation water, forming solid reaction products; 2. inject heavy nanoparticles (NPs) and CO2 in a homogeneous mixture to increase the density of the CO2-saturated brine and consequentially escalating the dissolution rate of the CO2; 3. divert the injected CO2 from a leaky compartment of the reservoir to an adjacent compartment, separated by a sealing fault; 4. mitigate the CO2 leakage through natural faults located far from existing wells, transporting a polymer-gel by using man induced hydraulic fractures to drastically reduce the permeability of the fault; 5. transport foam to a leakage site to block CO2 from leaking out of a point leak. The results will be published in an interactive web-based tool, to advise and inform operators and authorities on the novel options that we investigated for remediation and mitigation.

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