Completion fluid is a specialized liquid used in the oil and gas industry during the final stages of well construction. Its primary purpose is to maintain pressure in the wellbore and prevent the influx of formation fluids, ensuring the integrity of the well until production begins. This fluid is typically a mixture of water, salts, and various additives tailored to the specific conditions of the well. The composition of completion fluid can vary based on factors such as the type of reservoir and the desired properties, making it crucial for successful well completion and production operations.