Assessing Caprock Competency - A Comprehensive Geomechanical Study and Analysis in a Field in Middle East

Abstract When a well reaches its end of productive life, a well abandonment need to be safely executed to ensure the well does not pose any environmental or safety hazards. The process of well abandonment involves a thorough assessment and planning phase, which includes evaluating the well's condition and the abandonment procedure to ensure compliance with regulatory requirements and environmental standards. This process also involves isolating zones where oil and gas formations are present to prevent hydrocarbons from leaking to the surface and to avoid cross-contamination. This study aims to analyze the caprock integrity of Field G which consists of both clastic and carbonate reservoir. It addresses the critical need for sustainable development and abandonment practices that ensure long-term environmental and reservoir containment. The created caprock model and workflow eliminates the necessity of performing conventional full abandonment of existing well and drilling new well to access the deeper oil-bearing reservoirs in Field G. The study consists of comprehensive analysis of various logs and core data. Synthetic logs were created through numerical methods, followed by the computation of static and dynamic geo-mechanical properties. Triaxial and uniaxial tests were meticulously planned and executed on core plugs extracted from four different wells across Field G, serving as calibration data for the geo-mechanical model. A UCS model specific to Field G was developed and compared with established correlations in Middle East. Additionally, drilling data including FIT and LOTs were utilized to construct the pressure profile of Field G. The created model and workflow are then used to assess the caprock competency. Multiple competent caprocks were identified by studying the geo-mechanical properties of the rock. The UCS model that were generated specifically for Field G gives accurate prediction of the strength of such caprocks. This comprehensive caprock assessment has not only enabled us to make informed decisions regarding well deepening to appraise deeper reservoirs but has also facilitated partial abandonment of certain wells, allowing for production from shallower reservoirs without the necessity of drilling new wells. Additionally, the generated UCS model and correlation can be used as a reference for nearby fields to predict the rock strength in the absence of core data. This study provides valuable insights for the oil and gas industry regarding the assessment of caprock competency, aiding in informed decision-making during both development and abandonment stages. Such insights enable the industry to attain more reliable and cost-effective outcomes during abandonment processes, thereby contributing to sustainable resource management practices.