High-Performance Water-Based Drilling Fluid Proved an Environmentally-Friendly Alternative for Time-Sensitive Shales in Saudi Arabia

Abstract

As operators are drilling more and more complex wells in technically demanding basins; they are also looking to be cost effective and to minimize impact on the environment. This has driven the industry in recent past to develop and use high-performance water-based drilling fluids (HPWBDF). A drilling fluid that has performance like oil-based drilling fluids and environmental acceptance of water-based drilling fluids is the need of the times. In the whole Gulf region, wellbore instability is a major cause of nonproductive time. Drilling time-dependent shale formations have always been challenging; hole instability, tight hole, back reaming, and well packoff have been experienced in both vertical and highly deviated wells. These formations have a combination of reactive and dispersive clays in the shale formation, interbedded formation sequences, microfractures, and sometimes they can be tectonically stressed and overpressured with high-stress anisotropy. Such features make these formations time sensitive and highly unstable, thus they need multiple levels of inhibition. For this reason, oil-based drilling fluids are fluids of choice for many operators. In current times, the exceptional drillability of nonaqueous drilling fluids in high-angle, long-reach horizontal wells is offset by tremendously high logistical and waste-management costs that can account for half of the total drilling fluids cost. Recognizing these challenges, a novel HPWBDF was developed that could provide high level of inhibition and an excellent environmental and logistical footprint. This paper presents a successful application of a new HPWBDF using a unique triple inhibition approach. The system exceeded customer's requirements by successful execution of all well objectives. The client used this system in three consecutive sections instead of the single planned section. This solution has the potential to be used as an alternative to oil-based fluids in all similar formations drilled across the Middle East.