Maximizing well performance: quantifying the impact of drilling techniques on formation damage and productivity index in carbonate reservoir

Formation damage, caused by the invasion of drilling and completion fluids, significantly impacts reservoir productivity. This study investigated the relationship between drilling methods and formation damage using data from 54 vertical, horizontal, and directional wells in a carbonate reservoir. Core plug tests and well-test data quantify formation damage. The findings revealed that drilling and completion operations contribute to 50% of observed reservoir damages. Parameters such as total permeability, radial permeability, productivity index (PI), average reservoir pressure, and skin index were calculated for each well. Results demonstrated that wells drilled within underbalanced drilling (UBD) exhibit at least 300 bbl/d/psi higher PI than overbalanced drilling. Vertical wells with low radial permeability displayed the highest PI and average production pressure compared to horizontal and directional wells. Conversely, horizontal and directional wells showed higher damage rates and lower PI than vertical wells. Directional wells showed the lowest PI equivalent of 70 bbl/d/psi, vertical wells with the highest PI equivalent of 250 bbl/d/psi, and horizontal wells with an average PI equivalent of 150 bbl/d/psi. These results suggested using oil-based muds and UBD methods to reduce formation damage and optimize well productivity. The authors also emphasized the importance of proper fluid design and drilling method selection in preventing formation damage.