Thermal recovery techniques such as CSS (Cyclic Steam Stimulation) induce significant changes in the stress path at the reservoir formation due to the induced thermal stresses in the wellbore and surrounding area. The understanding of phenomena regarding these stress paths is crucial to ensure safe operation and optimization of well productivity. Therefore, stress path analysis in CSS entails a challenge related to the number of focal points throughout the reservoir in which the stress paths should be studied. The reduction on the number of focal points is an advantageous step to ensure the appropriate analysis in extensive reservoirs with multiple sands and layers with different geomechanical and yield parameters. In the proposed grouping strategy, temperature and pore pressure are found to be key variables when determining the sets of stress paths with a common phenomenological trending behavior. In the current case study located in Middle Magdalena Valley basin, this grouping strategy allows a comprehensive analysis of 3 sets of stress path strategically located on the borehole wall, inside and outside the steam front with the aid of numerical simulation software (CMG). Considering that stress paths usually represent a single focal point behavior within the reservoir, once this grouping strategy is implemented, an analysis of the whole reservoir is simultaneously performed during CSS.
Thermal recovery techniques are part of the production strategies implemented in heavy oil reservoirs. These reservoirs contain oil with high viscosity and density at reservoir conditions whose mobility is extremely low. A strategy to address this issue is increasing reservoir temperature to reduce residual oil saturation through mechanisms such as viscosity oil reduction, rock wettability changes, and gas solution drive. Thermal recovery techniques, in which steam injection is employed as a source of heat, are the most used for the exploitation of heavy oil fields. They are Cyclic Steam Stimulation (CSS), steam flooding and Steam Assisted Gravity Drainage (SAGD) [1].
CSS is a steam thermal recovery technique that requires less logistics for its execution since it is applied in a single well that performs the role of injector and producer well at different stages. The main objective of CSS is to heat as much of the reservoir as possible, guaranteeing the decrease in the viscosity of the crude oil in the reservoir. CSS considers three stages per cycle: injection, soak and production. During the first stage, a volume of hot steam (400-600 °F) is injected for a period of 1 to 4 weeks, after which the well is shut in and allowed to soak. The soaking period lasts for a few days and it aims to ensure high temperature proper distribution towards the well surroundings. The last stage, the production period, can last a few months [2].