Loss of circulation is one of the most common and costly problems encountered in oil well operations, but in many operating situations, wellbore strengthening is an effective and economical technique to prevent or mitigate the loss of circulation. Despite numerous experimental and modeling studies over the past three decades, differing views remain on the underlying mechanisms of circulation loss and well-strengthening. A comprehensive and rigorous review of the achievements and limitations of these fundamental studies is needed to aid engineers and researchers in the future development of this field. This article provides an up-to-date overview of fundamental research on circulation loss and well-strengthening. This review focuses primarily on experimental and theoretical studies, rather than field experience, to demonstrate the limitations of current knowledge in the field and to guide new research efforts. Fractures create escape channels for drilling fluids and are therefore an important mechanism for loss of circulation. This study provides fundamental information on the geological and rock mechanical properties of natural fractures. Fluid flow in fractures is discussed, especially the flow of non-Newtonian yield stress fluids such as drilling fluids. The effect of fracture roughness on fluid flow and particle transport is explained. The concepts of hydraulic and mechanical openings are introduced. These concepts play an important role when drilling fluid is lost through natural or artificial fractures. The effect of normal stress and shear stress on fracture permeability is shown. The effect of particle size distribution on particle migration in real fractures with rough walls is discussed. Proactive approaches are made prior entering the Hartha formation to prevent or mitigate the occurrence of the lost circulation. A broad statistical work, typical drilling fluid properties, and recommended operational drilling parameters are estimated to use during drilling through this formation. Moreover, corrective actions are determined for each type of mud loss provide effective remedies, minimize non-productive time, and reduce cost. The best lost circulation strategy for the Hartha formation is concluded and summarized depending on comprehensive statistical work, the most important courses of the international oil companies, technical papers, textbooks, and economic analysis evaluation to determine the successful remedies for each type of the losses. In addition, engineered solutions and practical techniques have been developed, which will contribute to giving a clear image and a coherent understanding regarding this complicated and costly problem in the Hartha formation.
Volume 15 | Issue 1
Pages: 7-17