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Alireza Rangriz-Shokri

PhD (2015)

Current position: Postdoctoral Fellow, University of Alberta

Research topic: Evaluation of post-CHOPS (Cold Heavy Oil Production with Sand) EOR Methods


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 hydrogeomechanical 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.



  1. Rangriz-Shokri, A. and Babadagli, T.: “Field Scale Modeling of CHOPS and Solvent/Thermal Based post CHOPS EOR Applications Considering Non-Equilibrium Foamy Oil Behavior and Realistic Representation of Wormholes,” J. Petr. Sci. and Eng., vol. 137, 144-156, 2016.

  2. Rangriz-Shokri, A. and Babadagli, T.: “Field-Scale Deformation Analysis of Cyclic Solvent Stimulation in Thin Unconsolidated Heavy Oil Reservoirs with Developed Wormhole Network,” accepted for publication in J. of Canadian Petr. Tech., vol. 54, no. 6, 341-350, 2015.

  3. Rangriz Shokri, A. and Babadagli, T.: “Modeling of CHOPS (Cold Heavy Oil Production with Sand) for Subsequent Thermal/Solvent Injection Applications,” J. of Canadian Petr. Tech., vol. 53, no. 2, 95-108, 2014.

  4. Rangriz-Shokri, A., Babadagli, T. and Jafari, A.: “A Critical Analysis of the Relationship between Statistical and Fractal Fracture Network Characteristics and Effective Fracture Network Permeability,” accepted for publication in SPE Res. Eval. and Eng., 2016.

  5. Rangriz-Shokri, A. and Babadagli, T.: “Sensitivity and Uncertainty Analysis of Cyclic Solvent Stimulation for Post-CHOPS EOR: Application on an Actual Field Case,” accepted for publication in SPE Economics and Management, 2016.

  6. Rangriz-Shokri, A. and Babadagli, T.: “Evaluation of Thermal/Solvent Applications with and without Cold Heavy Oil Production with Sand (CHOPS),” SPE 158934, 2012 SPE Energy Conference, Developing Resources for Sustainability, Port-of-Spain, Trinidad, June 11-13, pp. 17.

  7. Rangriz-Shokri, A. and Babadagli, T.: “An Approach to Model CHOPS (Cold Heavy Oil Production with Sands) and post-CHOPS Applications,” SPE 159437, 2012 SPE Annual Tech. Conf. and Exh., San Antonio, TX, 8-10 Oct., pp. 12.

  8. Rangriz-Shokri, A. and Babadagli, T.: “Modeling Thermal and Solvent Injection Techniques as Post-CHOPS Applications considering Geomechanical and Compositional Effects,” SPE 165534, 2013 SPE Heavy Oil Conf., Calgary, AB, Canada, 11-13 June.

  9. Soh, Y., Rangriz-Shokri, A. and Babadagli, T.: “A New Modeling Approach to Optimize Methane-Propane Injection in a Field after CHOPS,” SPE 181322, 2016 SPE Ann. Tech. Conf. and Exh., Dubai, UAE, 26-28 Sept.

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