No description available.

Kimberlites have been recently discovered beneath 100m of glacial sediment at Fort a la Come, Saskatchewan, Canada. Crater and extra-crater facies have been intersected in borehole core, interstratified with coastal and marine sediments of Cretaceous age. Extra-crater kimberlite is very rare, and particularly well preserved at Fort a la Come. It is encountered in five borehole intersections drilled by Rhonda Mining Corporation, sponsors of the Operation Fish Scale project, which included kimberlite research at the University of Leeds. The regional setting and geological description of six kimberlite borehole intersections are presented. In addition, the broad geodynamic conditions and the stratigraphic context are described, and from these a model for kimberlite eruption is constructed. The kimberlites are then described at a range of scales from stratal thickness and disposition, to ultra-fine diagenetic mineral growth. A textural classification is then applied to the deposits. The volcanology of the Fort a la Cone kimberlites are then discussed: these are unusual in that the craters are preserved, and are broad and flat, rather than steep sided tapering cones. A new term, pateran crater, and process of evolution is proposed for these and other kimberlites of similar morphology. The survival of these volcanic edifices in the sedimentary environment is also considered. The geochemistry of the kimberlites is presented, both bulk rock, and over 450 analyses of individual mineral grains by electron microprobe. These minerals are mostly gamet, ilmenite and pyroxene, of megacryst, kimberlite, crust, mantle peridotite and eclogite origin. The mineral chemistries are compared to those found in other kimberlites around the world, and the nature of the cratonic lithosphere is described. The P-T and compositional characteristics of the lithosphere are further refined from diamond and garnet trace element chemistry in collaborative works with Taylor and Griffin, described herein. Economic aspects of the kimberlites are reviewed, and all the conclusions are presented in time order, from diamond growth in the Archean, crustal evolution in the Mid-Proterozoic, Early Cretaceous magma generation and eruption, to Late Cretaceous reworking and burial.

This work describes the development and validation of a computational model for vertical borehole heat exchangers in residential ground-source heat pump energy systems. Due to the size and shape of vertical borehole heat exchangers, their operation thermally impacts a large volume of surrounding soil and thus discretized models have largely been confined to short-term transient simulations, such as the case of a thermal response test. The proposed model employs a computationally efficient physics-based models at variable spatial dimensions which can be used for long-time simulation of the ground heat transfer. The model can generally be considered as a composition of three separate domains: the borehole domain, which combines one-dimensional, three-dimensional and equations-based physics, the near-field soil domain, which resolves three-dimensional transient heat conduction and the far-field soil domain which is modelled as one-dimensional axisymmetric transient heat conduction. The main purpose of this work is to present each component of the model and validate their behaviours and assumptions through a combination of comparison to experimental data, highly cited published works, and well-known analytical models. The complete composite model ignores the three-dimensional effects of fluid heat transfer, and the axial heat transfer in the far-field in order to reduce the computational effort, and the level of uncertainty introduced by each simplification is explored. Finally, to support the composite model, a new method determining the thermal impact of the borehole operation mentioned previously was devised and presented alongside the model development and validations. This method, based on the previously defined thermal impacting radius, improves the consistency and theoretical foundation of the value’s definition based on a system energy balance, rather than local temperature conditions. / Thesis / Master of Applied Science (MASc)

This research describes the development and application of a numerical modelling method for angled borehole heat exchangers in ground-source heat pump systems. Inclining the boreholes relative to the vertical axis presents an opportunity to reduce the ground level footprint of the borehole field thus allowing for the installation of geothermal systems in retrofit applications or under buildings with small footprints. The commercial code COMSOL was used to develop the computational model. A series of validation and verification studies were performed to ensure the accuracy of the modelling approach. Simulations were conducted under constant and transient heat injection, where the effect of energy load imbalance is analyzed. Additionally, the effect of discontinuous loading with natural and forced recovery cycles is investigated. When exposed to a constant heat injection rate, configurations of angled borehole heat exchangers initially perform the same as vertical borehole heat exchangers. Then, there is a relatively short period where the angled configurations have slightly decreased performance due to increased thermal interaction in the near surface. At longer times, however, there is a significant benefit in using angled borehole heat exchangers as a result of the increased ground volume in the lower portion of the field. Under transient loading conditions, the conclusions were the same as constant heat injection, although the differences were smaller when the energy loading was balanced. However, when the loading was cooling dominated, by year 10 there was a significantly better performance observed for the angled boreholes. This indicates that the configurations of angled borehole heat exchangers can withstand a higher intensity of imbalanced energy loads compared to vertical configurations. Discontinuous loading was investigated by varying the length of time heat injection would occur on a daily basis. These daily perturbations led to small performance losses in the angled boreholes due to the increased thermal interaction in the near surface. Furthermore, imposing a forced recovery on the system by circulating fluid while heat injection was off did not significantly affect the fluid temperature or ground temperature. / Thesis / Master of Applied Science (MASc)

In this work, an application of the algebraic reconstruction technique to a borehole reconstruction problem is considered. The formulation of the borehole problem gives the attendant electromagnetic wave equations in matrix form. The algebraic reconstruction technique is used to reconstruct a solution. Three sources of errors are identified in the reconstruction process. Suggestions are made which will help minimize or predict the effects of these errors. General limitations of the algebraic reconstruction technique are discussed. The limitations in terms of the borehole problem are explained. Practical limitations for the borehole problem are thus obtained and quantified mathematically. It is found that even in some practical situations, the borehole reconstruction process is impossible.

Boreholes in the vicinity of a nuclear waste repository must be reliably sealed to prevent rapid migration of radionuclide contaminated water from the vicinity of the repository to the accessible environment. Few data currently exist regarding the effectiveness of borehole sealing. The objective of this research was to assess the performance of borehole seals under laboratory conditions, particularly with regard to varying stress fields. The approach used to evaluate borehole seals was to compare flow through a sealed borehole with flow through intact rock. Granite, basalt, and tuff were tested, using either cement or bentonite as the seal material. The main conclusions reached as a result of the experiments is that currently existing materials are capable of forming high quality seals when placed under laboratory conditions. Variation of triaxial stress state about a borehole does not significantly affect seal performance if the rock is stiffer than the seal material. Temperature/moisture variations (drying) degraded the quality of cement seals significantly. Performance partially recovered upon resaturation. A skillfully sealed borehole may reasonably be expected to be as impermeable as a fractured rock mass (subject to site-specific verification). The influence of relative seal-rock permeabilities provides insight into important seal parameters. A plug one order of magnitude greater in permeability than the rock through which it passes resulted in an increase in flow through the borehole and surrounding rock of only 1 1/2 times as compared to the undisturbed rock. Since a sealed borehole and its surrounding rock are only a small part of the total rock mass, the effect is even less pronounced. One of the simplest ways to decrease flow through a seal-rock system is to increase the length of the seal. Significant remaining questions include field emplacement techniques; field vertification of plug quality; plug performance over long time periods, particularly with respect to temperature/moisture variations and chemical stability; and radionuclide sorption capabilities. Scale effects are also important, as shafts and drifts must be sealed as well as larger diameter boreholes.

No description available.

Acoustic, electromagnetic (EM), and nuclear open-hole measurements are affected by fluids saturating near-wellbore porous and permeable rock formations, including hydrocarbons, water, and mud filtrate. Fluid invasion effects can be quantified and advantageously used to estimate petrophysical properties of the invaded rock formations. This dissertation incorporates the physics of water-base mud- (WBM) and oil-base mud- (OBM) filtrate invasion to the simulation and inversion of borehole EM measurements. We assume vertical boreholes penetrating clastic hydrocarbon- or water-bearing formations subject to either WBM- or OBM-filtrate invasion. The simulation of EM measurements in the presence of mud-filtrate invasion considers three different approaches: (1) piston-like invasion profiles, where we solely consider invaded- (flushed) and virgin- (uncontaminated) zones, (2) two-phase immiscible displacement and salt mixing between the invading WBM filtrate and connate water, and (3) invasion of single or multi-component OBM-filtrate into a formation saturated with multiple hydrocarbon components wherein the individual components are first-contact miscible. The last two approaches honor the physics of mudcake growth as well as the petrophysical properties that govern the process of multi-phase, multi-component fluid-flow displacement and include the presence of irreducible, capillary-bound and movable water. Electromagnetic measurements are simulated from spatial distributions of electrical resistivity calculated from the simulations of mud-filtrate invasion using clean- or shaly-sand water-saturationresistivity models. Inversion of petrophysical properties is posed as the nonlinear minimization of quadratic objective functions that quantify the misfit between EM measurements and their simulations. In the case of WBM piston-like invasion profiles in water-bearing formations, combined inversion of array-induction resistivity and spontaneous potential (SP) measurements yields connate water electrical resistivity and Archie’s cementation exponent. Permeability is calculated from the inversion of array-induction resistivity measurements assuming immiscible fluid-flow displacement of WBM into hydrocarbonbearing formations. Accurate reconstructions of layer-by-layer permeability are primarily constrained by the availability of a-priori information about time of invasion, rate of mud-filtrate invasion, overbalance pressure, capillary pressure, and relative permeability. This dissertation also quantifies the influence of petrophysical and fluid properties on borehole resistivity measurements acquired in the presence of compositional mixing of OBM filtrate invading partially hydrocarbon-saturated rock formations. Numerical simulations of OBM-filtrate invasion are performed with an adaptive-implicit compositional formulation that allows one to quantify the effects of additional components of mud-filtrate and native fluids on EM measurements. Perturbations of petrophysical and fluid properties enable the quantification of rock wettability changes due to OBM-filtrate invasion and their effect on the simulated induction resistivity measurements. Finally, simulations of induction resistivity measurements in the presence of OBM are compared to the corresponding measurements in the presence of WBMfiltrate invasion. The latter analysis allows us to estimate a realistic flow rate of OBMfiltrate invasion that is responsible for the variation of induction resistivity measurements as a function of their radial length of response. The combined simulation of the physics of mud-filtrate invasion and EM measurements provides reliable estimates of true formation resistivity and hence of water saturation, thereby improving the assessment of in-place hydrocarbons reserves. / text

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M. Sc.)--University of Hong Kong, 2003. / Also available in print.