Assessing the impact of drilling methods on formation damage - A case study of an Iranian oil field reservoir

Abstract

Abstract Formation damage, resulting from the invasion of drilling and completion fluids, significantly affects reservoir productivity. This study investigates the relationship between drilling methods and formation damage using data from 54 vertical, horizontal, and directional wells. Core plug tests and well test data quantify formation damage. The findings reveal that drilling and completion operations contribute to 50% of observed damages in the reservoir. Parameters such as total permeability, radial permeability, productivity index (PI), average reservoir pressure, and skin index were calculated for each well. Results demonstrate that wells drilled under underbalanced drilling (UBD) exhibit at least 300 bbl/d/psi higher PI than overbalanced drilling. Vertical wells with low radial permeability display the highest PI and average production pressure compared to horizontal and directional wells. Conversely, horizontal and directional wells show higher damage rates and lower PI than vertical wells. Directional wells exhibit the lowest PI at 70 bbl/d/psi, followed by horizontal wells at 150 bbl/d/psi, while vertical wells exhibit the highest PI at 250 bbl/d/psi. These results suggest the use of oil-based mud and UBD methods to mitigate formation damage and optimize well productivity. The authors emphasize the importance of both proper fluid design and drilling method selection in preventing formation damage.