Ryan van Zanten

Engineering Drill-in Fluids to Improve Reservoir Producibility

Preventing formation damage is the primary objective of a drill-in fluid. Damage can occur through many different mechanisms including emulsion blocks, water blocks, polymer/filtrate/particle invasion, precipitates, and improper wetting of the formation. Damage can be remediated by stimulating the formation through fracturing, acidizing or improving flow-back with chemical treatments; however, these post-drilling treatments can significantly increase well construction costs. Ideally a reservoir drill-in fluid will be tailored to prevent formation damage and protect the producibility of the well. Current methods such as viscosifying filtrate can be engineered to minimize filtrate invasion along with utilizing acid-degradable fluid loss control polymers/bridging particles. Verifying compatibility between the drill-in fluid and formation fluids can help prevent blockages from precipitates or scale. Although it can be minimized, filtrate invasion in water-based drill-in fluids is typically higher than in oil-based drill-in fluids, and such invasion can adversely impact producibility. This paper investigates the effect of chemical treatments added to the fluid that alter formation wettability and/or eliminate emulsion blocks in oil wells or water blocks in gas wells whilst being penetrated during the drilling process. By applying these treatments, water- and brine-based fluids can achieve return permeabilities similar to oil-based drill-in fluids. The invading aqueous filtrate can be used as a production enhancement tool, allowing us to achieve improved formation producibility. This paper describes the development of a unique technique to chemically alter the drill-in fluid such that the invading filtrate alters the producing rock to optimize production. This can reduce or eliminate the need for remedial treatments and can decrease damage from certain fluid additives such as lubricants and corrosion inhibitors.