Drilling fluid, also known as mud, plays a crucial role in drilling wells by removing cuttings, controlling formation pressures, stabilizing the wellbore, and providing cooling and lubrication to the drill bits. Accurate measurement of drilling mud flow is essential for efficient drilling operations, considering the density changes, voids, and gas bubbles that may occur. Similarly, during casing operations, cement is used to secure the steel casing pipes, and precise measurement of cement flow and density is crucial for process control.This book aims to provide an overview of preventive and corrective methods for drilling and cementing through fractured zones. It also explores advancements in drilling and cementing technology to address issues like lost circulation. These advancements include techniques such as aerated drilling fluid, casing while drilling, managed pressure drilling, expandable tubular, and lightweight cement slurries. The book seeks to equip readers with knowledge about these methods and technologies to improve drilling and cementing practices.