The majority of footage drilled directionally is achieved by using bent-housing, positive displacement motors. This established technology uses oriented drilling intervals to maintain well trajectory. These intervals can be difficult and time consuming in many drilling environments; however, the economic advantages of this system often preclude the use of more capable rotary steerable assemblies. Operators have long needed a system that fills the widening gap between the two technologies.A new system of wellbore directional control has been developed that uses continuous string rotation above a positive displacement motor and bent sub. Path deviation is achieved by brief variations in the rate of penetration (ROP) that occur once during each rotation of the bent sub. Bit advance is increased during each rotation causing the bit to drill faster in the targeted direction. This directed variation in ROP allows manipulation of hole trajectory while the bent housing and drillstring are continuously rotating. Steering is accomplished by managing pressure fluctuations within the drillstring, creating slight oscillations in the flow rate through the mud motor. These controlled fluctuations in flow rate allow variations in drilling parameters to steer the well in any targeted azimuth.The goal of this system is to eliminate all oriented drilling in applications up to 3 degree per 100 feet by employing a low risk, low cost method that maximizes ROP and hole cleaning. At the Gas Technology Institute (GTI) Catoosa Test Facility in Oklahoma, drilling tests yielded successful well trajectory manipulation, delivering up to 3 degree per 100 feet of controlled directional performance in both 6 1 / 8 " and 8 1 / 2 " hole diameters. Because a standard bent housing assembly was used, oriented drilling was always available as needed. This allowed a redundancy in directional control (oriented or rotary), widening the operational scope and technical capability of the system.

Mud motors, in conjunction with a bent sub, have been used for over 40 years to directionally steer wells to a target location. Mud motor technology is well understood and has seen significant improvements over the years. Rotary steerable tool technology is relatively new to the oilfield and improvements are still being made to enhance performance and reliability. The significant advantage of rotary steerable tools is that the drillstring is continuously rotated throughout the drilling operation. A new system for wellbore directional control has been developed which uses continuous drillstring rotation above a positive displacement motor and bent sub. This new system offers many advantages of a rotary steerable system but also offers the proven technology of a positive displacement mud motor. Steering is accomplished by managing pressure fluctuations within the drill string, creating slight oscillations in the flow rate through the mud motor. These controlled undulations in flow rate allow high frequency variations in drilling parameters to steer the well in any targeted azimuth. If the objective cannot be achieved using rate of penetration modulation in rotary mode, then the motor can still be oriented using the more conventional means of stopping rotating, sliding against the borehole until the motor is in its new orientation, and returning to rotating. This paper will discuss the advantages and disadvantages of the new system compared to both conventional mud motor and rotary steerable technology. The paper will also discuss the early field trials of the new system in various hole sizes and discuss how selected parameters affect performance.

Mud motors have been used for decades to help steer wells in a desired direction. They are typically oriented with a bent sub in the motor and are pointed in the planned direction to kick-off the well or drilling section. They use a combination of rotating and sliding to keep the well on target and, depending on various drilling and formation parameters, may need to slide the majority of the time to maintain hole projection. Sliding often creates issues with hole cleaning, ledging, and decreased rate of penetration (ROP). Rotary-steerable tools, on the other hand, continuously rotate in the hole eliminating many of the problems associated with an oriented positive displacement motor (PDM). A new system for wellbore directional control has been developed that uses a positive displacement motor and a bent sub to provide continuous rotation throughout the wellbore. This new system offers many advantages of a rotary-steerable system but also capitalizes on the proven technology of a positive displacement mud motor. Steering is accomplished by managing the pressure fluctuations within the drillstring, creating slight oscillations in the flow rate through the mud motor. These controlled undulations in flow rate allow high-frequency variations in drilling parameters to steer the well in any targeted azimuth. If the planned objective cannot be achieved using ROP modulation in rotary mode, then the motor can still be oriented in the desired direction and slid, using the more conventional mud motor orienting technique. This paper will review several operations where the new steering system was used to help drill the well. It will discuss the operational challenges of drilling the wells, as well as how the new system helped overcome those challenges.

Based on input from key operators in the Middle East region, a new rotary steerable system (RSS) was launched after a compressed development schedule. This paper describes the development and introduction of the larger tool sizes needed for both onshore and offshore hole sections, including hole sizes from 12 in. and up, in the Middle East. It also outlines the deliberate design of the tool for local assembly and repair. Large diameter (9-1/2 and 11 in.) RSS designs used an existing, smaller design for Middle East applications in both offshore and onshore wells as a basis. When designing these new sizes, engineers took note of lessons learned with smaller sizes of the tool and incorporated design elements for local manufacturing, assembly, and repair. The resulting simple, modular construction enables increased levels of local content and provides for significant reductions in transportation, and therefore associated emissions. Of course, although local content and sustainability are highly desirable, performance is essential, and this paper describes case histories demonstrating how well the new tool worked in real-world Middle East applications. In one notable example, the newly introduced 9 1/2-in. diameter RSS was used to drill an offshore section in the Gulf of Arabia. The tool was mobilized after two older generation RSS had become stuck for days. Consisting primarily of argillaceous limestone, the formation had a history of stuck-pipe events. The new RSS was recommended for this application because of a slicker construction, with a fully rotational bias unit, minimal bottom hole assembly (BHA) stabilization, and an optimized junk slot area, which together help to reduce stuck-pipe risks. The tool drilled to the target depth in a single run, thereby achieving all directional requirements. Notably, after reaching the target depth, the assembly was tripped out of the hole without any requirement for backreaming. This seamless exit, in turn, indicated achieving a smooth wellbore. Other case histories demonstrate results with both new sizes of this tool. The paper also discusses in detail the ability to repair locally and engage the local supply chain. Specifically with Middle East applications in mind, a new, simple RSS design in large diameter versions has demonstrated success in offshore and onshore applications across the region. The design has also proven capabilities for manufacturing and repair local to operations, which enables maximizing in-country value, optimizing use of the tools, and energizing local supply chains.