--> 3-D Geology and Petroleum Chemistry of the Alberta Peace River Oil Sands — Investigating Odours and Emissions

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3-D Geology and Petroleum Chemistry of the Alberta Peace River Oil Sands — Investigating Odours and Emissions

Abstract

Our team created a 3D geological model to investigate the contribution of geology and petroleum chemistry of heavy oil and bitumen to odours and emissions in the Peace River area of Alberta. This project was initiated by the Alberta Energy Regulator after a formal inquiry into increased odour and emission complaints from area residents. The results of this investigation aided the regulator in making informed decisions regarding gas conservation requirements in the area. An investigation during the formal inquiry suggested odours and emissions were directly related to oil from a specific source-rock (Gordondale Member); but the stratigraphic and structural complexity of the geology suggested other possible explanations should be examined. The heavy oil and bitumen deposits straddle the Sub-Cretaceous Unconformity and are adjacent to the Peace River Arch. The 3D model highlights the complexity, making it apparent that the Peace River oil sands are likely sourced by more than one source-rock and the source-oils have undergone varying degrees of mixing and homogenising. Oil mixing is related to migration while homogenising is related to biodegradation. It is not possible to separate source oils in the reservoir based on source-rock chemistry. For this reason, we developed a small petroleum sampling program focused on the odorous compounds and oil properties rather than source-rock issues. Our sample program analyzed oil and gas from heavy oil and bitumen wells for reduced sulphur compounds (RSCs) and volatile organic compounds (VOCs). The data show that total RSC concentrations increase when oil is heated (to reduce oil viscosity). Oil density and viscosity data (acquired in-house) were also evaluated within the model. These data show that the density and viscosity of the oil is related to the depth of the deposits in the subsurface, with more dense and viscous oil located at shallower depths. We created a 3D odours and emissions assessment profile by integrating the data and the model. This profile identifies the volume in subsurface with the highest probability for encountering oil with higher density and viscosity, which require heating at production. Since the data show an increase in odorous compounds with heating, this high probability volume indicates where the potential for odours and emissions is highest. The 3D model was key to linking geological complexity, oil geochemistry, oil viscosity and odorous compounds.