Evaluation of Longstring Production Casing Design For AFK-2 Well at PT Pertamina Geothermal Energy

Abstract

This study quantitatively evaluated the structural integrity and feasibility of the casing design for Well AFK-2. This objective was achieved through a deterministic analysis to calculate and validate Safety Factors (SF) against various load scenarios as stipulated by industry standards. The analysis revealed that the designed casing program possesses high structural integrity. Key findings indicate that the 13-⅜” production casing, utilizing the superior L-80 grade over the minimum required K-55, exhibits a substantial safety margin, with SF values of 1.757 for burst, 2.193 for collapse, and 10.47 for tension. Furthermore, the liner sections, including the 10-¾” and 8-⅝” strings, were found to be secure against buckling risks, with SF values of 6.26 and 6.08 respectively, which are well above the critical threshold of 1.2. The design also proved robust against thermal loads, with induced stresses remaining safely within the material's elastic limits. In summary, this study confirms that the casing design implemented in Well AFK-2 is technically feasible and safe, comprehensively meeting all performance criteria. The broader implication of these findings is the affirmation that a conservative design philosophy specifically, selecting material specifications that exceed minimum requirements is a highly effective and quantifiable risk mitigation strategy. The primary contribution of this work is the presentation of a well-documented engineering case study that quantitatively validates how a robust design approach significantly enhances wellbore integrity, particularly for high-complexity applications such as geothermal wells.