Rotary steerable systems provide advantages, opportunities

Once a niche-market technology reserved for difficult or complex wells, rotary steerable drilling systems today have become a mainstream service that offers advantages for a number of applications. They offer the ability to drill directionally and continuously without having to stop or slow down to change direction, allowing uninterrupted drilling with continuous weight on the bit, while at the same time providing real-time log data.

According to Noble Downhole Technology, Well Director is a state-of-the-art 3D rotary steerable drilling tool capable of meeting the growing demand for advanced directional drilling technology. The company says the technology provides precise directional drilling control, increased rates of penetration, and a smoother less tortuous well bore. The tool's near-bit sensors make continuous adjustments in the azimuth and inclination headings to accurately steer the well to the desired targets. This enables operators to accurately and efficiently drill long horizontal and directional wells that were previously not cost effective. In addition, the use of this tool as a vertical control tool greatly improves the efficiency of drilling deep vertical wells in heavily faulted formations.

Noble says it has significantly upgraded the tool since its acquisition in 2002, including new high temperature (175° C) sensors and electronics. It can be operated in conjunction with other service companies M/LWD and formation evaluation tools, providing increased flexibility when choosing suppliers.

Pathfinder Energy Services

Pathfinder Energy says its PathMaker 3D Rotary Steerable system is the culmination of five years of research and development. Its primary application is to provide the operator with the technology to steer the wellbore precisely into the targeted reservoir, without interrupting drilling operations. It replaces the conventional "steerable motor" for all on-hore and offshore drilling applications, while providing the operator with a quality wellbore. The PathMaker is compatible with all of PathFinder's formation evaluation services.

Some of the features the company lists are:

• Used in a "point the bit" configuration for improved hole quality
• Push the bit configuration available
• Simple and reliable downhole programming without interrupting the drilling operation
• Continually transmits directional position, which is displayed real-time at the surface
• Can be used as a stand-alone device with any MWD system
• Can effectively steer in hole sizes up to 1 in. over gauge
• Through contact with the borehole wall, the non-rotating stabilizer blades provide a real-time hole calliper measurement
• Compatible with any PathFinder LWD services and BHAs.

Some of the main benefits described are:

• Consistent quality and smooth wellbore
• Increased rate of penetration.

Precision Drilling

Precision Drilling says its Revolution service includes the first 4 3/4-in. slimhole rotary steerable system to use point-the-bit technology. According to Precision, extensive laboratory drilling tests, BHA software modelling, and field experience show point-the-bit mode provides better hole quality, longer bit life, lower bit vibration, and more efficient rock cutting than push-the-bit mode.

Point-the-bit mode uses a pivot stabilizer between the bit and rotary steering tool to orient the drill bit axis with the axis of the hole. This set-up improves wellbore quality by reducing ledging, spiraling, tortuosity, and gauge problems associated with push-the-bit systems, the company says.

Simulation and field experience has been used to optimize BHA designs that achieve efficient face cutting of the bit in point-the-bit mode. These designs help the Revolution slimhole RSS maximize penetration rates and eliminate inefficient side-cutting forces, improving bit life and stability while reducing harmful vibration that can damage other BHA components, such as LWD tools.

Point-the-bit systems ultimately drill a smoother wellbore that is more nearly gauge than push-the-bit systems. A smooth wellbore allows the Revolution RSS to consistently steer the bit to the exact target location, extending well sections and improving reservoir optimization.

The Revolution system's compact design reduces BHA complexity, while placing critical LWD formation evaluation components close to the bit. The result, the company says, is higher than average ROP and fewer doglegs than in wells drilled with conventional drilling motors.

Virtually all rotary steerable systems employ a borehole contacting, or bias, device for providing radial force, the company says, and the orientation and deflection of this device must be measured. The Revolution slimhole RSS uses a new method of measuring orientation and deflection, employing dynamic measurements from sensors rotating with the drive shaft and having no physical connection with the bias unit. This enables the entire annular space to be used for the sleeve positioning hydraulics, the company says.

Rotary Steerable Tools

Rotary Steerable Tools (RST) was incorporated in 1998 and says it is becoming the leading provider of simply constructed, reliable, effective and low cost, directional drilling tools, including a rotary steerable system that improves the practice of directional drilling.

RST says its tool design is simple and low cost. The tool has no practical limitations on flow rate, rotary speed or weight on bit, the company says. Communication to the tool to change tool face heading is made through simple RPM commands. The tool has less than 70 total components and is field serviceable. It is capable of producing a dogleg severity as high as 8°/100 ft, and can also be used to keep wells vertical. The through-bore nature of the tool means valuable pump pressure is available for hole-cleaning, and new technology such as thru-bit-logging is enabled. The simple, low-cost features of the RST tool allows the expansion of the proven technical benefits of rotary steerable systems from current high cost, complex well profiles to lower cost environments and more conventional directional well profiles, the company says.

The tool is an instrumented, near-bit stabilizer, with three main components: a rotating mandrel, an eccentric inner sleeve, and a weighted, non-rotating outer housing. The tool works by controlling the orientation of the eccentric, inner sleeve, which offsets the mandrel and thus the bit, in the desired direction. Rotation of the inner sleeve to change tool face orientation is made by a geared, brush-less DC motor powered by lithium batteries.

Schlumberger

Schlumberger's suite of full-rotation rotary steerable services – the PowerDrive family – delivers leading-edge technology for all directional drilling environments, the company says. The company says the products offer exceptional rates of penetration and efficient hole-cleaning in the most demanding applications – kickoff from vertical, open-hole sidetracks, tangent sections, slimhole extended-reach drilling, long lateral sections, and drilling under harsh conditions at elevated temperatures.

Developed to increase run length, optimize wellbore placement, and reduce drilling time, the PowerDrive X5 system provides significant reliability and efficiency gains, Schlumberger says. The automatic inclination hold and efficient downlink functions minimize surface interaction to maintain directional control while drilling ahead, thus increasing productive time on bottom. This fully rotational system incorporates a real-time 360° azimuthal gamma ray measurement for geosteering applications enabling drillers and geologists to identify bed boundaries quickly. A triaxial sensor package close to the bit provides accurate azimuth and inclination information enabling fast, responsive directional control in either automatic or manual operation mode, and tight TVD control. Design efficiencies of the control and bias units facilitate longer runs, optimum wellbore placement, and reduction in drilling time.

PowerDrive vorteX, the newest addition to the Schlumberger rotary steerable family, has a fully integrated high-torque power section that converts mud hydraulic power to additional mechanical power downhole. Benefits are faster drilling and a reduction in nonproductive rig time. Power from the rig combined with the downhole high-torque power section provides a significant increase in available torque, rotation speed, and downhole power at the bit. Schlum-berger says this prevents damaging downhole vibrations and lowers the risk of drill string fatigue and excess casing wear in hole sections with high doglegs. The system includes an optional inclination hold function, which allows a tangent or horizontal section to be drilled automatically, without intervention from the directional driller. Automatic downhole control makes it possible to drill a hole section at a higher ROP and with greater accuracy than a conventional surface-operated control setup, the company says. The system can be stabilized at any of four locations along its length, depending on directional drilling needs. In addition to performance drilling in hard-rock formations, PowerDrive vorteX is suitable for rigs with lower power specifications.

The PowerDrive Xceed RSS is a special-application tool that extends the benefits of Schlumberger's fully rotating steering systems to applications in harsh, rugged environments where externally steered mechanisms reach their performance limits. Featuring a totally enclosed internal steering mechanism and rugged, field-proven electronics, the tool provides significant wear and reliability advantages in abrasive, hot, and high-shock applications. PowerDrive Xceed is ideally suited for openhole sidetracking, steering in over-gauge hole, and in soft-formation applications, the company says. Minimal wellbore dependence also allows Xceed to be run with bicenter bits.

Rotary steerable systems have been on the market for over five years and have hundreds of successful runs and millions of feet drilled to verify their reliability.

null

Target Energy Inc.

The Target/Smart Drilling Rotary Steer-able System (RSS) provides a new generation of downhole closed loop push-the-bit RSS technology for 6-1/8-in. and smaller well bores. According to Target Energy, the system provides the benefits of improved rate of penetration, better hole cleaning, smoother well bores, and more accurate well placement, with an overall cost reduction in drilling operations and delivery of superior wellbore quality.

The system is based on proven steering physics and uses four hydraulic pistons combined with a downhole electrical and hydraulic power generation system and state of the art magnetometer and accelerometer attitude measurement technology. The system is designed to steer the bit from the current measured point to the desired position along a trajectory at a predefined build rate.

Another rotary steerable system, RockSTar, incorporates the critical benefits of the more complex point-the-bit rotary steerable systems into a cost effective package, the company says. Now, the company says, the most cost constrained projects can benefit from the savings of rotary steerable technology that incorporates:

• No sliding while drilling
• Rotational deviation eliminates need to alter drilling parameters for control of tool face
• Drilling parameters can be maintained to maximize ROP
• No hole spirals or fractional orientation ledging
• Continuous rotation minimizes torque and drag
• Continuous rotation improves hole cleaning
• Better hole-cleaning reduces ECD
• Rotation reduces friction-increasing ROP
• Constant drill pipe movement reduces potential for differential sticking
• Ability to perform directional control at greater reach
• Allows more complex well profiles with lower risk
• Elimination of torque effect on tool face allows slimmer drill strings to greater depths.