Development of a Wellbore Stability Prediction Model Using Multiple Regression with Missing Core Samples: A Case Study of the Shunbei Oil and Gas Field

Abstract

ABSTRACT The Shunbei oil and gas field, characterized by its intricate deep fault-karst reservoirs and fractured carbonate lithology, presents formidable challenges to wellbore stability during drilling and completion phases, precipitating adverse events such as wellbore collapse and fluid loss. This study embarks on addressing the paucity of data integral for effective wellbore stability prediction in this region, employing a tripartite methodological approach: identification of pertinent data and influential factors, enhancement of multiple regression accuracy, and selection of controlling factors. The study revealed that the multiple linear regression model delivered the most precise predictions for both the leakage rate and well diameter expansion rate. Crucial factors such as geodetic coordinates, drilling pressure, and azimuth were identified as exerting substantial influence on wellbore stability. By scrutinizing primary controlling factors and underscoring the crucial role of drilling pressure and displacement in averting collapse and leakage, this study provides invaluable insights applicable to actual production settings. This study, while enhancing understanding of wellbore stability through analyzing key factors, does not delve into quantitative control strategies. Nevertheless, it provides a practical framework for better management of wellbore collapse and leakage in Shunbei oil and gas field. INTRODUCTION Meeting the global energy demands requires exploration and development of oil and gas fields (Cui et al., 2023). However, drilling and completion of deep fault-karst reservoirs such as the Shunbei field (Baozeng et al., 2020) present significant challenges due to wellbore instability issues. These issues include wellbore collapse, fluid loss, and other prevailing problems (Lixin, 2020), which can lead to extensive equipment damage, increased drilling and operational costs, and endanger the safety of personnel. The wellbore instability issues faced in the Shunbei field are primarily due to the fractured carbonate lithology, which exhibits fragility and poor mechanical properties (Yingtao et al., 2019). Precise prediction of wellbore instability and fluid loss in such formations is essential for efficient field development. The field of rock mechanics and wellbore stability has a long history, dating back to the early 20th century, when the first recorded studies focused on the stability of oil and gas wells (Cheatham, 1984).