Thermal stimulation techniques are widely used to exploit Western Canadian heavy oil assets. These techniques rely on injection of steam into the formation, inducing complex geomechanical stresses in the reservoir and surrounding strata during the life cycle of the project. In SAGD wells, the collapsed oil sand around the liner undergoes a stress buildup which causes gradual sand compaction. The stress buildup is influenced by several factors such as the in-situ stresses, reservoir poroelastic and thermal expansion, and reservoir shear dilation. However, the impact of stress level and anisotropy around the liner is not properly accounted for in previous research on slotted liner design. This paper investigates the effect of anisotropic stress buildup around slotted liners on their sanding and plugging performance under multiphase flow conditions.
A Scaled Completion Testing (SCT) facility was utilized to emulate multi-axial stress and multiphase flow conditions near the sand control liner. Brine, oil, and gas were used as flowing fluids. Sand-pack samples were prepared using commercial sands by matching the particle size, shape and, composition of the McMurray Formation oil sands. A constant lateral stress and several axial stresses were applied to simulate the stress conditions around the liner. The three-phase flow condition was used to evaluate the role of the steam breakthrough on the liner performance.
Experimental results indicate the critical role of stress conditions around the liner on its sanding and plugging responses. Results show gradual sand-pack compaction with the gradual increase of the axial stress. Higher axial stresses result in a smaller amount of produced sand, which can be attributed to the stronger inter-particle frictional resistance, hence, stronger and more stable sand bridges behind the slots. The higher compaction results in a lower porosity and permeability, hence, altering the plugging and sanding response of the liner. Also, higher retained permeabilities are found for stronger anisotropic stress conditions. Besides, it is found that the three-phase flow condition could cause a stronger fines migration and production, compared to single-phase flow.
The results of this study indicate that the stress and multiphase flow effects are crucial factors in the evaluation of slotted liner performance. The findings from the innovative experimental studies provide insights into the practicability of evaluating slotted liner performance with the consideration of sophisticated field conditions and optimizing the selection of the slotted liner aperture for the entire well lifespan.