The Mauddud reservoir in the Raudhatain and Sabiriyah fields of north Kuwait includes production layers that were historically exploited using vertical wells. As lower layers begun producing water, horizontal producers from upper layers were planned. A recent simulation study was performed for electrical submersible pumps (ESPs) in the reservoir. ESPs must be placed vertically and as near to the target layer as possible for maximum sweep effect, and as a result, greater build rates in the build section of the well were required to enter the reservoir laterally at the optimal depth. With a requirement for these wells to be drilled with a rotary steerable system, a high build rate (HBR) rotary steerable system (RSS) is required.
An upgraded true point-the-bit (PTB) RSS was run for the first time with a polycrystalline diamond compact (PDC) bit in a matched system. A logging-while-drilling (LWD) suite was used while drilling the build section and steer into the target reservoir. The RSS was modified to increase the effective bend angle at the bit and optimize the fulcrum point geometry for high dogleg capability. Bottomhole assembly (BHA) modeling was performed to optimize the stabilization while simultaneously managing stresses in the BHA. Bit designs were optimized with an integrated bit-BHA model to provide sufficient lateral aggressiveness and good hole quality. Extensive planning and BHA optimization exercises were performed to address the challenge.
The initial field tests were performed in Kuwait, and the planned trajectory was initially designed with a +/- 10 deg/100 ft build rate. The proposed system was successfully run and exceeded requirements; While drilling the build section, the real-time LWD correlation showed the target formation coming in 19 ft shallower than was initially estimated, requiring a higher than planned dogleg to land the well in the target zone. The RSS deflection was increased to increase the dogleg output, based on the updated target location. The upgraded RSS responded immediately and the system was able to deliver in excess of 12 deg/100 ft build rate, producing a smooth curve at high rate of penetration (ROP) and with low vibration – achieving the target TVD required. A high build rate capability using the PTB system was proven while sustaining the PTB advantages, including superior hole quality, enhanced directional control, and reduced drilling time.
This new development provides a unique capability to the industry in a true PTB RSS system with high dogleg capability. Good hole quality and steerability of a PTB RSS can now be achieved simultaneously in high dogleg applications. Good hole quality combined with precision in wellbore control improves drilling performance and completion installation in high dogleg applications. This capability enhances the project economics and enables increased production potential.