This book investigates the limits of formation damage encountered with the various types of drilling fluids components. Remedial work was performed to restore the oil bearing formation characteristics. The objective of this book can be summarized in the following points: 1. Evaluation of various reservoir rocks towards the impact of the formation damage, caused by various types of drilling fluids, on the oil and / or gas productivity. 2. Delineate the pore channels blocking by the fine particles which may either caused by drilling fluids directly or released by filtrate invasion from the pore walls. 3. Minimize the formation damage using different treatment methods to improve the properties of formation productivity.