Top of cement influence on APB mitigation in high pressure and high temperature oil wells

This work presents a study on the influence of Top of Cement (TOC) in mitigating Annular Pressure Build-Up (APB) in wells subjected to high pressure and high temperature (HPHT) conditions. Oil and gas exploration in HPHT wells poses significant engineering challenges, including an increased occurrence of APB. Under extreme circumstances, APB can compromise casing integrity, leading to oil leakage into the marine environment and jeopardizing safety and operational continuity. The objective of this study is to comprehend how TOC height influences APB behavior. Additionally, in cases where the cement top does not cover the previous casing shoe (open shoe), the study examines how fluid leak-off affects APB response. The methodology consists of four main stages: i) literature review on characterizing and modeling APB in HPHT wells; ii) implementation of a semi-analytical model proposed in the literature to calculate APB considering cement effects and formation leak-off; iii) modeling scenarios with varying TOC heights; and iv) analyzing results to observe the relationship between APB, TOC heights and casing safety factors. These results are compared with those from widely used commercial software in the industry. The results obtained with the implemented model demonstrate that positioning the TOC below the previous casing shoe effectively reduces APB. However, caution is warranted when reducing TOC height, as it is crucial for wellbore stability. Thus, this study contributes to developing a methodology for evaluating the impact of TOC height and leak-off on APB, providing guidance for future research and practical applications in the industry, and enhancing safety and operational efficiency in HPHT wells.