Well Integrity Evaluation Through a Completion Redesign for Cyclic Steam Stimulation in Non-Thermal Wells of the Zuata Principal Field in the Orinoco Oil Belt - Venezuela

Motivated by the need to increase oil production through the implementation of Cyclic Steam Stimulation (CSS) in 54 non-thermal horizontal prospective wells within the Zuata Principal Field of Orinoco Oil Belt in Eastern Venezuela, this work undertakes a mechanical integrity evaluation of the "non-thermal type well" under various CSS scenarios in order to evaluate the tubular's design limits and identify failure points. Subsequently, a completion adequacy proposal is developed and evaluated to guarantee the well integrity. A representative well from the sample ("non-thermal type well") was selected for this study. Its current design was subjected to mechanical evaluation using a commercial simulation software under three thermal loads or CSS scenarios (with injection rates of 200 and 400 t/d for cumulative volumes of 5,000, 7,500 and 10,000 t/cycle, respectively). All scenarios considered the use of Vacuum Insulated Tubing (VIT). Additionally, a case study was run, incorporating a completion adequacy proposal aimed at guaranteeing that the design limits of all tubular elements within the well architecture were not exceeded. For the scenarios evaluated, tubular's temperature profiles were generated under CSS conditions. Analysis of temperature profiles revealed that for a fixed total injection volume, a higher injection rate translates to a more efficient process due to reduced heat transfer to the tubular elements. Therefore, a rate of 400 t/d, with 80% steam quality (550°F and 1,030 psig at injection wellhead) and 10,000 t/cycle was selected as the operational scheme. A comprehensive evaluation of the design limits of the tubulars was conducted to identify potential failure points, considering the analysis of axial compressive loads and the axial safety factor. It was determined that the critical elements exceeding the design limits are the 9-5/8″ production casing and the 9-5/8″×7″ production liner hanger. Considering the high probability of failure under the current design, an additional simulation scenario was run. This scenario considered completion adequacy by installing a tieback thermal packer to isolate the existing non-thermal liner hanger 9-5/8″×7″ and, finally, installing VIT string positioned 1500 feet away from the production casing shoe, in order to mitigate adverse effects on the latter. Under this final scenario, the design limits of the tubulars are not breached, ensuring well integrity. The mechanical integrity evaluation conducted on the "non-thermal type well" in the Zuata Principal Field of the Orinoco Oil Belt provides preliminary technical justification for extending CSS processes to non-thermal wells in the area, which have been previously limited to thermal wells.