Increased world-wide interest in reducing the carbon-footprint of human activities has driven the coal-fueled energy industry to transition to a natural gas fueled future. Coupled with the continually increasing energy demand, the interest in alternate sources of natural gas has gained momentum. Microbially enhanced coalbed methane (MECBM), which aims at microbially converting in situ coal to methane provides one such alternate source of natural gas. Feasibility of MECBM as a viable technology is two-pronged, focusing on associated microbiology, and flow-governing reservoir response. The general advance of research in this area has thus far been from a microbial perspective, where coal-to-methane bioconversion has been successfully reported for several coal types worldwide. However, insights into reservoir properties governing flow and transport of fluids in a MECBM reservoir is missing. Given that coal is both the source and reservoir rock of the produced biogenic methane, a sound knowledge of the effect of bioconversion on flow governing properties of coal is decisive from a production perspective. Evaluating the flow governing reservoir response of a MECBM reservoir is the focus of the work presented in this dissertation. In order to investigate the effect of bioconversion on the Darcian flow regime existing in the natural fractures in coal, two experimental studies were undertaken. First, variation in coal’s flow governing micro- and macro- porosity was investigated using high-resolution scanning electron microscopy. The observed changes were quantified and the expected change in permeability of coal post-bioconversion was estimated. In the second set of experiments, the sorption-induced-strain response of coal pre- and post-bioconversion was studies. Finally, the experimental data was used to model and predict the geomechanical-coupled flow behavior of a MECBM reservoir during bioconversion and production of the produced biogenic methane. Experimental results from the imaging study revealed that bioconversion results in swelling of the coal matrix. This reduces the cleat (macroporous fracture) aperture post-bioconversion, reducing the permeability of the coal significantly. This validated the recently reported results, where measured permeability of coal packs and coal cores dropped by ~70% post-bioconversion. Bioconversion, however, resulted in increase in the cleat width of fractures greater than 5 microns wide, which constituted <5% of the fractures imaged. This is indicative of the possibility of enhanced reservoir performance in artificially fractured coal formations or, ones with wide-aperture fractures, like depleted coalbed methane (CBM) reservoirs and abandoned mines. Investigation into the sorption-induced-strain response of coal revealed suppression of the strain response post-bioconversion. Results from helium and methane flooding revealed that bioconversion softens the coal matrix, reducing the Langmuir pressure and strain constants post-bioconversion. The modeling exercise revealed that the depletion induced the permeability increase commonly associated with producing CBM will be suppressed post-bioconversion. Detailed analysis of the behavioral variation in multiple reservoir parameters was used to define the ideal condition, beyond which the reservoir flow during biogenic methane production improved. Additionally, a rating system is proposed, which can be used to rank coal deposits to rate their suitability for bioconversion from a flow perspective.

Groundwater chemistry on the Niagara Peninsula has been identified as highly mineralized in comparison to groundwaters collected from the same bedrock formations elsewhere in southern Ontario. Three geochemical zones were discerned using hierarchical cluster analysis and other geochemical and isotopic methods. The Escarpment Zone, located along the Niagara and Onondaga Escarpments, is characterized by unconfined aquifer conditions, parameters reflective of surficial contaminants, including road salt, and elevated HCO3, DOC, NO3-, coliform bacteria and tritium. In contrast, in the Salina Zone thick, low-permeability sediments and gypsiferous bedrock results in highly mineralized groundwaters with Ca-SO4 geochemical facies and elevated S2-, Ca2+, Mg2+, K+, Na+, SO42-, Cl-, Br-, Sr2+, NH4+ and CH4. The Guelph Zone contains the lowest electrical conductivity of the three zones and elevated F-. Outliers exist with groundwater geochemistry that differs from the local geochemical zone and the host aquifer. These sites have elevated SO42- (>1000 to 5200 mg/L) with depleted δ34SSO4 (-2.2 to 14.3‰ VCDT) signatures that differs starkly from Devonian and Silurian evaporites (~20 to 32 ‰) in the host formations. This exogenic SO4 was identified in a cross-formational northeast – southwest linear trend crossing three major groundwater flow systems. The lack of down-stream impact in these systems and tritium groundwater ages that are typically only decades old indicate a young, non-geological origin and implicate anthropogenic activities. Additionally, nine samples were identified with elevated methane concentrations and δ13CCH4 signatures within the thermogenic range. As thermogenic methane is not produced within shallow aquifers and would be short-lived in the presence of the ubiquitous sulfate, these samples imply recent upward migration of methane from depth through vertical conduits. Taken together, the evidence supports large-scale upward movement of fluids in the centre of the Niagara geochemical anomaly and more sporadic upward transport of gases over a wider area of the peninsula. The most likely vector is through corroded and leaking casings or boreholes of abandoned (century) gas wells that are common across the peninsula. / Thesis / Master of Science (MSc)