Real Time 3D Observations of Portland Cement Carbonation at CO Storage Conditions.

Depleted oil reservoirs are considered a viable solution to the global challenge of CO storage. A key concern is whether the wells can be suitably sealed with cement to hinder the escape of CO. Under reservoir conditions, CO is in its supercritical state, and the high pressures and temperatures involved make real-time microscopic observations of cement degradation experimentally challenging.

Influence of Chemical, Mechanical, and Transport Processes on Wellbore Leakage from Geologic CO Storage Reservoirs.

Wells are considered to be high-risk pathways for fluid leakage from geologic CO storage reservoirs, because breaches in this engineered system have the potential to connect the reservoir to groundwater resources and the atmosphere. Given these concerns, a few studies have assessed leakage risk by evaluating regulatory records, often self-reported, documenting leakage in gas fields. Leakage is thought to be governed largely by initial well-construction quality and the method of well abandonment.

Brownian Dynamics of a Suspension of Particles with Constrained Voronoi Cell Volumes.

Solvent-free polymer-grafted nanoparticle fluids consist of inorganic core particles fluidized by polymers tethered to their surfaces. The attachment of the suspending fluid to the particle surface creates a strong penalty for local variations in the fluid volume surrounding the particles. As a model of such a suspension we perform Brownian dynamics of an equilibrium system consisting of hard spheres which experience a many-particle potential proportional to the variance of the Voronoi volumes surrounding each particle (E = α(Vi-V0)(2)).

Determination of diffusion profiles in altered wellbore cement using X-ray computed tomography methods.

The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration.

Fracture-scale model of immiscible fluid flow.

We present a method for modeling immiscible fluid flow in narrow fractures. The method combines a parallel-plate flow model with a recoloration approach adapted from multiple-component lattice-Boltzmann methods. The resulting numerical method is straightforward to implement and accurately reproduces the relevant fluid behavior.

Chemical and mechanical properties of wellbore cement altered by CO₂-rich brine using a multianalytical approach.

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.