Physical Modelling of CO2-Cyclic Solvent Inject in post-CHOPS reservoirs
Creators: Cartagena Perez, Daniel Felipe
Publisher: name: University of Alberta Library
Year: 2024

<p>This thesis looks for modelling physically the cyclic solvent injection as enhanced oil recovery (EOR) technique used in unconsolidated heavy oil reservoirs, particularly those subjected to Cold Heavy Oil Production with Sands (CHOPS) methods. CHOPS reservoirs are characterized by their low recovery factors (5-15%) due to the challenges posed by unconsolidated sand formations, high sand and water production rates, and limited reservoir energy. The geomechanics of CHOPS reservoirs involve the formation of high-permeability channel-like structures known as wormholes, resulting from sand production during production operations. These geomechanical characteristics contribute to challenges such as reservoir compaction, sand control issues, and formation collapse. In the other hand, the presence of those wormholes limits the applicability of some EOR techniques due to their low efficiency.<br>
This thesis comprises four interconnected papers that address critical aspects of reservoir engineering, geotechnical experimentation, and material characterization to overcome these challenges and provide a set of tools to model the post-CHOPS reservoirs in an experimental environment with the use of a geotechnical centrifuge for physical modelling.<br>
The approach used in this thesis is mainly experimental, aiming to provide tools and materials that enable further investigation into post-CHOPS reservoirs. To achieve a comprehensive understanding of post-CHOPS reservoirs, which present multiple challenges (e.g., geomechanical conditions, sand production, and the presence of wormholes), a new geotechnical centrifuge cell was designed, manufactured, assembled, commissioned, and tested. This new cell has the capability to induce an anisotropic stress state at 30 times Earth&#39;s gravity while producing through a central wellbore connected to wormholes. The experiment also involves the use of foamy oil. Additionally, to achieve a better representation of poorly cemented reservoirs, this thesis presents a new procedure to 3D print rocks, along with the mechanical and hydraulic characterization of this material. <br>
The results show that the developed geotechnical centrifuge worked effectively in all its components. Radial flow was confirmed using well testing techniques, and an anisotropic stress state was imposed on the sample, validating the applicability of this new cell. At the same time, the 3D-printed rocks developed in this thesis demonstrated similar elastic parameters to some poorly cemented reservoirs. These rocks exhibited degradation of strength and stiffness with long exposure to canola oil, stability under isotropic creep tests, permeability within the range for Western Canada reservoirs, and an even distribution of the binder.<br>
Thus, this thesis presents two novel contributions to the study of reservoir geomechanics: (i) a new geotechnical centrifuge cell with triaxial stress capabilities and radial flow, and (ii) a new 3D-printed material that emulates poorly cemented reservoirs. Additionally, the reviews include some field cases of CO2-CSI (Cyclic Solvent Injection) that have never been presented in the technical literature, and the potential applications for the geotechnical centrifuge in reservoir engineering as a programmatic aspiration.</p>