With an objective to shorten directional intervals, operators place greater demand on higher Build Up Rates (BURs). The section just before the pay zone involves the most intensive directional work, pushing rotary steerable systems to their capability limits. This paper focuses on a particular interval of hard and soft interbedded carbonates that provides a significant challenge for conventional Polycrystalline Diamond Compact (PDC) bits to provide consistent build up rate and good borehole quality on rotary steerable systems. Throughout this paper we demonstrate the engineering process of designing a bit to increase buildup rate capabilities of rotary steerable systems and improving drilling efficiency through interbedded carbonate formations. The engineering process involved reviewing the critical issues of this application to assure a sound solution. This included: Current build up rates versus Rotary Steerable Systems (RSS) steering capability. Vibrations generated by conventional PDC bits being deployed in the field. Specific cutting structure, depth of cut limiters and gauge requirements for different RSS drive types. Formation strength analysis. Parameters used in drilling the section. Roller cone insert and PDC interaction of the hybrid bit with the formation and how formation deformation generated by one interacts with the other. Roller cone insert design aimed specifically at carbonate formation drilling Various hybrid drill bit and Bottom Hole Assembly (BHA) combinations were evaluated with state-of-the-art drilling response simulator to review the buildup rate capabilities combines with the bit and BHA interaction. The best combination was then successfully trialed on several wells, proving significant improvement compared to current performance with conventional PDC bits. The optimized hybrid bit and BHA combination eliminated drilling vibrations in intervals where extreme vibrations were witnessed with conventional PDC bits, significantly increasing drilling efficiency. Improved torsional stability reduced the load on the directional tools improving the ability to achieve the required doglegs. In softer shale where RSS with conventional PDC's had to control parameters while using maximum steer force to achieve target dog legs of 7°/100ft, the hybrid drill bit achieved 10°/100ft while utilizing only 70% of the steer force. The hybrid drill bit has been proven to be successful with both push-the-bit and point-the-bit RSS systems. Hybrid drill bits have proven to be a solution to problems and limitations of both conventional PDC and roller cone bits in directional drilling. Based on recent refinements in the drilling mechanics of hybrid drill bits to further improve their interaction with directional drilling systems, engineering selected this emerging technology to overcome the challenges in this particular application.

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 ϩ/-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.

Promotion of horizontal well drilling started with inflow control device (ICD) completion to boost the hydrocarbon production as per the KOC 2030 strategy. Drilling these wells revealed many technical issues leading to stuck pipe due to improper hole cleaning. The rate of penetration (ROP) in the buildup and lateral sections was erratic. Drilling a pilot hole and performing pipe-conveyed logging runs were the main factors contributing to excess rig time. It was observed that drain hole cleaning methods and drilling time optimization needed to be improved. These factors increased rig time by about 40 while drilling many horizontal wells in the North Kuwait (NK) horizontal operation, adding significant costs to the well budget. While drilling these horizontal wells, well design was optimized and the drilling team applied the optimized design that increased hole-cleaning effectively, improved ROP and reduced the logging time. The 6⅛-in. and 8½-in. motorized rotary steer-able systems (RSS) and bottomhole assembly (BHA) systems ran for the first time in Kuwait, drilling 8½-in. build section from Mutriba to the Upper Burgan top formation and 6⅛-in. section in Mauddud carbonates has dynamically avoided down-hole tool failures, doubled the average ROP, and reduced non-productive time (NPT). The pilot hole section was designed and drilled in two phases. In the first section a gamma ray tool identified the formation tops. The second section (zone of formation interest) was then drilled using an 8½-in. tool with a triple-combo RSS BHA. This approach reduced the extensive wireline or tough logging condition (TLC) runs and increased ROP by slimming down the borehole size. The hole-cleaning method was modified by combining pumpout techniques with heavy-weighted pills (MW+2 ppg). This technique was used in horizontal wells, resulting in reduced drilling time and well cost.