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Evaluation of post-CHOPS (Cold Heavy Oil Production with Sands) Enhanced Oil Recovery Methods Open Access


Other title
field scale application
steam injection
cyclic solvent injection
CHOPS modeling
fractal wormhole
Type of item
Degree grantor
University of Alberta
Author or creator
Rangrizshokri, Alireza
Supervisor and department
Dr. Tayfun Babadagli (Civil and Environmental)
Examining committee member and department
Dr. Fanhua Zeng (Petroleum System Engineering, U of Regina)
Dr. Ergun Kuru (Civil and Environmental)
Dr. Huazhou Li (Civil and Environmental)
Dr. Ryosuke Okuno (Civil and Environmental)
Dr. Lijun Deng (Civil and Environmental)
Department of Civil and Environmental Engineering
Petroleum Engineering
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Due to its lower cost, the cold heavy oil production with sands (CHOPS) method is a common primary production recovery technique, not only in Canada where it originated, but also in many other countries including Venezuela, Kuwait, Russia, and China. However, this method has several practical limitations. It continuously changes the geomechanical and petro-physical properties of the reservoir due to the sand produced, resulting in high permeability channels known as wormholes. In addition, this method has a low oil recovery factor (5-15 %) and this entails further recovery techniques. Thermal methods after CHOPS are not usually favourable due to heterogeneity and reservoir instability. In addition, CHOPS wells are not completed for thermal (steam) operations. The CHOPS method is typically applied in thin formations in which heating by injected steam is characteristically inefficient. Solvent injection possesses similar problems caused by heterogeneity and cost. An option could be the hybrid application of steam/solvent. Assessment of this technique first requires a realistic modeling of the CHOPS process. Due to dynamic changes in reservoir properties, no valid model was available to accurately simulate field-scale CHOPS production. Therefore, a part of this thesis presents a quick workflow for CHOPS modeling to investigate efficient EOR/IOR (Enhanced/Improved Oil Recovery) methods after CHOPS. To achieve this, we first propose a partial-dual porosity approach coupled with algorithms for wormhole generation to create realistic static reservoir models. After generating fractal wormhole patterns of different kinds using a diffusion limited aggregation (DLA) algorithm, they were introduced into a reservoir model. Based on fractal analysis, novel upgridding procedures for wormhole network in partial-dual porosity models were introduced. After validation of the models using data obtained from a field in Alberta, several preliminary post-CHOPS scenarios including thermal, solvent, and thermal/solvent hybrid applications were simulated. In addition, a 3D geomechanical model was used to calculate the stress distribution in the history matched field. The hydro-geomechanical model was then used for field development planning, reservoir management and assessment of near wellbore regions during cyclic injection and production. The field-wide deformation and stress changes were analyzed in deep overburden, cap rock, and reservoir to show the influence of local stress orientations in soft and stiff layers. Next, an experimental set-up consisting of a sand-pack with different configurations of complexity of wormhole patterns was designed. The experiment was aimed to mimic cyclic solvent stimulation at reservoir conditions. The sand-pack experiments were numerically simulated and effective diffusion coefficients were obtained. To generate accurate predictions in field-scale simulation, an up-scaling procedure from laboratory results of the cyclic solvent injection process was suggested. The overall findings suggest that an improved heavy oil recovery could be achieved using combined light and heavy solvents in CHOPS reservoirs. Steam (or hot-water) was found to play a positive role in solvent retrieval. Finally, an uncertainty screening procedure was performed to assess the feasibility of cyclic solvent stimulation as a post-CHOPS method. An economics model was developed and after-tax NPV (Net Present Value) of the field at the end of cyclic solvent stimulation process was calculated. Such calculations have the priority to oil recovery factor or cumulative oil production as it could incorporate costs and sales simultaneously by performing continuous discounting and allow the asset holder to maximize NPVs and select the best development strategy.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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