SUMMARYThis paper describes a fully coupled finite element/finite volume approach for simulating field-scale hydraulically driven fractures in three dimensions, using massively parallel computing platforms. The proposed method is capable of capturing realistic representations of local heterogeneities, layering and natural fracture networks in a reservoir. A detailed description of the numerical implementation is provided, along with numerical studies comparing the model with both analytical solutions and experimental results. The results demonstrate the effectiveness of the proposed method for modeling large-scale problems involving hydraulically driven fractures in three dimensions.

Defining chemical and mechanical alteration of wellbore cement by CO(2)-rich brines is important for predicting the long-term integrity of wellbores in geologic CO(2) environments. We reacted CO(2)-rich brines along a cement-caprock boundary at 60 °C and pCO(2) = 3 MPa using flow-through experiments. The results show that distinct reaction zones form in response to reactions with the brine over the 8-day experiment. Detailed characterization of the crystalline and amorphous phases, and the solution chemistry show that the zones can be modeled as preferential portlandite dissolution in the depleted layer, concurrent calcium silicate hydrate (CSH) alteration to an amorphous zeolite and Ca-carbonate precipitation in the carbonate layer, and carbonate dissolution in the amorphous layer. Chemical reaction altered the mechanical properties of the core lowering the average Young's moduli in the depleted, carbonate, and amorphous layers to approximately 75, 64, and 34% of the unaltered cement, respectively. The decreased elastic modulus of the altered cement reflects an increase in pore space through mineral dissolution and different moduli of the reaction products.

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