Drill String Optimization Across Multilateral Wells Breakthrough a New Benchmark of Performance and Enhanced Operation Integrity: Middle East Specific

Abstract The drilling construction process in specific Middle Eastern fields presents unique challenges, especially when drilling multilateral wells. These wells require the use of a two string configuration, 5" drill pipes to drill the long 8-1/2" curve section followed by the use of 4" DPs to drill the lateral sections. This leads to increased operational risks and extend drilling time in order to lay down 5" DPs after drilling the curve section. This manuscript outlines the implemented solutions, highlighting technical benefits and cost savings achieved by optimizing the drill string design. Traditionally, the 8.5-inch landing section is drilled with 5-inch DPs, while the 6.125-inch laterals require drilling with either all 4" DPs or with tapered string of 5-inch and 4-inch DPs. In the case of tapered string, due to the shallow design of the 7-inch top-of-liner (TOL), each lateral requires an additional trip for inserting 4-inch DPs. A comprehensive study of torque and drag (T&D) and hydraulics was conducted to evaluate the feasibility of drilling both the curve and lateral sections exclusively with 4-inch DPs. Additionally, finite element analysis (FEA) was performed to assess dogleg severity (DLS) capabilities and shock levels. A full risk assessment was also conducted to address gaps related to health, safety, and environmental (HSE) factors and equipment quality. Performance evaluations show that 4-inch DPs, when used in the curve sections, outperformed 5-inch DPs by requiring less torque and reducing shock and vibration. Moreover, the compact size of 4-inch DPs helped in minimizing stick-slip incidents and mechanical-specific energy, thus enhancing drilling efficiency over traditional 5-inch DP applications. These improvements increased operational efficiency, resulting in cost savings of 0.5 days per well by eliminating the need for P/U and L/D additional 5" DPs. Further savings of 1–1.5 days per well were achieved by eliminating unnecessary trips for repositioning 4-inch DPs in wells where tapered string was used to drill the lateral sections. Additional savings were realized by removing the requirement for packer utilization to modify the blowout preventer (BOP) ram, reducing rig time by one full day. Overall, the reduction in operational activities led to improved operational integrity, enhanced drilling efficiency, and increased cost-effectiveness. This study provides a comparative evaluation of 4-inch versus 5-inch DPs, demonstrating how an optimized drill string selection can enhance performance while mitigating operational risks and costs. This paper attempts to highlight the benefits of utilizing 4-inch drill pipes (DPs) in both the landing and lateral sections of multilateral wells. Through controlled simulations, finite element analyses and field data, the study evaluates and compares the performance of 4-inch versus 5-inch DPs in 8½-inch landing sections. The findings related to hole cleaning, vibration management, and mechanical performance are based on this specific context, and the solutions and lessons presented can be applied globally following comprehensive risk assessments to validate their efficacy in similar well configurations.