Unconsolidated oil sands: Vertical Single Well SAGD optimization

Several recovery processes have been proposed for heavy oil and oil sands de-pending on the reservoir and fluid properties, among which steam-assisted gravity drainage (SAGD) is being widely used. Surface mining is the best approach in very shallow depths. However, there are hydrocarbon deposits too shallow for SAGD and too deep for mining which require special techniques to recover the hydrocarbon eco-nomically. In addition, relatively huge reserves are left behind as stranded reserves. Those reserves are usually characterized with weak caprock integrity and without enough pay thickness for SAGD to be economically viable. This study focuses on a recently developed technique, called Vertical Single Well SAGD, for enhanced production from oil sands. Sensitivity analysis has been performed, using CMG-STARS, to evaluate the condition that will help achieving high efficiency in Vertical Single Well SAGD. This system consists of a vertical well with multiple highly permeable vertical planes, called inclusions, which are used for steam injection and liquid production pur-poses. Steam is injected into the upper part of the formation and the drained liquid is collected at the bottom of the inclusions. Unlike the conventional steam chamber ge-ometry in SAGD processes, steam moves outward from the inclusion faces into the formation and tends to move laterally out and vertically upward over time. Simulation studies of the system shows that success of such technique depends on the inclusion dimensions as well as injection rate and pressure. This study investigates the effect of inclusion dimensions and steam properties on the performance of such a process. Res-ervoir simulations of realistic reservoir conditions show promising results in terms of cumulative steam oil ratio (CSOR) and production rate. Peak oil production occurred at around 100 days from startup and CSOR dropped to under 3.0 m3m3 after 100 days. The optimum inclusion dimensions and the best injection scenario. Furthermore, a brief investigation of rock and fluid properties of Athabasca oil sands has been performed, with a focus on absolute permeability measurements. An understanding of the parameters involved in reservoir flow capacity such as permeabil-ity variation with effective stress and with temperature, is crucial in the development of a coupled thermal-geomechanics model. This will provide a better prediction of bi-tumen production. Changes in stress and deformation caused by fluid injection or pro-duction in unconsolidated sand formations will result in alteration of pore structure and permeability. In this study, steady state technique is implemented to measure ab-solute permeability of bitumen-free Athabasca sand as a function of effective stress.