Challenges of oil recovery in mature assets continue to increase, requiring horizontal wells to be drilled for longer intervals. To improve the overall production in Kuwait, horizontal injector wells are required in some carbonate reservoirs in north Kuwait fields with the main objective of driving reservoir pressure in cases where aquifers cannot contribute to sustained oil recovery. Drilling several injector wells with long lateral sections was found to be the best approach to improve reservoir sweeping efficiency and drive the pressure regime for sustaining higher production levels.

Historically, all horizontal wells drilled in similar reservoirs utilized oil-based mud (OBM), which was instrumental in reducing torque and friction along the lateral sections. Recently, all injector wells in the area were switched to water-based mud (WBM) systems in the lateral to reduce reservoir damage and improve injectivity and to enable the use of microimaging logging tools while drilling. This switch, together with limited drilling rig capability and geological uncertainty, posed major challenges on the deliverability of the horizontal section to planned total depth (TD). The operator, in collaboration with the drilling services provider and other service providers, completed a substantial planning phase to optimize the well design and make it achievable using current resources.

The bottomhole assembly (BHA) was modeled, with iterations made to enhance the capability of drilling long laterals with proper weight transfer without sacrificing well stability or directional control. To overcome the challenge of drilling the long lateral section without the need for intermediate trips, the tool string design was customized for additional robustness and durability.

Completed in two runs, the 6979 ft section was considered to be the longest lateral in north Kuwait ever achieved at the time. Maintaining the well in the desired trajectory, the motorized rotary steerable system was used to achieve a rate of penetration (ROP) improvement above the field average and within the allowable torque limit permitted, reaching the required total depth successfully. The bit and BHA selection and design were both critical to success. The subject reservoir known for high rock stresses and varying local formation dip angles posed a challenge to maintain the well on the desired trajectory due to unpredictable changes in the BHA tendency. Rotary steerable system (RSS) automation through the use of closed loop and cruise control features helped minimize human intervention. These features enable the RSS to automatically react and change downhole settings to track target inclination.

This paper discusses the planning, design and execution of the subject well, in addition to the added value and resulting improvement in reservoir sweeping efficiency.

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