Using analytical hierarchy process and multi influencing factors to hole instability in Cambro-Ordovician TFT Oil Field

Abstract

The challenges posed by wellbore instability in the Cambro-Ordovician formations of the Tin Fouyé Tabankort (TFT) Oil Field in the Illizi Basin of Algeria are the subject of this thesis. The research applies two advanced decision-making methodologies—Analytical Hierarchy Process (AHP) and Multi-Influencing Factors (MIF)—to systematically analyze and prioritize the complex factors contributing to hole instability during drilling operations. The study begins by examining the geological setting of the TFT field, exploring its unique tectonic history and depositional environments. It then provides a comprehensive analysis of wellbore instability mechanisms, including tectonically stressed formations, mobile formations, unconsolidated zones, and pressure-related collapse. The research identifies and categorizes key factors affecting stability as lithological, mechanical, petrophysical, and drilling fluid-related. Through application of the AHP methodology, the study establishes a hierarchical structure of these factors and determines their relative importance through pairwise comparisons. Complementing this approach, the MIF technique is employed to analyze the network of influences between factors, identifying which elements exert the most significant effects within the system. Using real data from Well TFT-481, the research demonstrates the practical application of these methodologies, providing a comprehensive risk assessment framework for wellbore stability in the challenging Cambro-Ordovician formations. The findings offer valuable insights for optimizing drilling operations in the TFT field and similar geological settings, potentially resulting in substantial cost savings, reduced non-productive time, and improved operational safety