Underbalanced Drilling and Its Advancements: An Overview

Abstract

Ever increasing global energy demand associated with depletion of conventional hydrocarbon resources drives exploration and production (E&P) industry to invent advanced new technologies in frontier areas of drilling, production and reservoir engineering to enhance hydrocarbon production from unconventional resources or depleted reservoirs. Demand to produce from a low pressure marginal reservoir and the discoveries of naturally fractured reservoirs lead to the development of new drilling techniques like underbalanced drilling along with other technological advances. Underbalanced drilling (UBD) technology can overcome a number of problems encountered during drilling, which is otherwise impossible with conventional overbalanced drilling. However, in-depth understanding of the characteristic behavior of different components during operation is an essential criteria for efficient application of this technology. In drilling operation, drilling fluid plays a very important role in controlling the entire operation efficiently without any interruption or damage to the reservoir. Foam-based drilling fluid, one of the most favored techniques of UBD needs a thorough study for its applicability and smooth functioning under bottom hole condition. Foam fluid is very much unpredictable for its very sensitive rheological behavior, specifically for small variation in pressure, temperature, and composition along with other parameters during drilling. Hence, utmost care should be taken for proper designing of foam-based fluid, failing of which may negatively affect the process. Present paper deals with the developments of foam fluid as an efficient drilling fluid since its inception, composition and rheology, merits and demerits, comparison with conventional fluids which will help the researchers working in the field to get the intensive information without consulting a large literature.

Keywords: Underbalanced drilling, Foam, Formation damage, Differential sticking, Fluid loss