Scientific Drilling International announced the commercialization of its HALO rotary steerable system (RSS) at the 2018 Society of Petroleum Engineers Annual Technical Conference & Exhibition held in September in Dallas. Consisting of an integrated steering unit and MWD survey package, with azimuthal gamma ray geosteering and pressure-while-drilling capabilities, the HALO system is fully assembled, calibrated and qualified before delivery to the rig site. This minimizes bottomhole assembly makeup time and helps mitigate HSE risks associated with rig floor operations.
“The importance of rotary steerable systems in unconventional shales has become increasingly important, especially as operators are drilling longer laterals to extend their pay zone yield,” CEO Phil Longorio said.
The new HALO RSS “helps meet operators’ reliability and economic challenges, while yielding more efficient, smoother directional wellbores, resulting in faster well construction and completion operations,” he said.
Building a complex curve in the Marcellus
Available in a 6½-in. collar size, the HALO system drills standard 8½-in. and 8¾-in. hole sizes as well as the 97⁄8- in. intermediate hole size.
The HALO system is a high-dogleg severity (DLS) RSS capable of operating in 77⁄8-in. hole sizes, providing a cost savings of about 15% to the operator over the standard 8½-in. and 8¾-in. options. Cost savings are recognized both on the drilling and completions sides due to smaller tools and casing strings. Historically, the 77⁄8-in. hole size has not been popular because RSS tools were not capable of drilling both the curve and lateral sections in one run, so operators drilled the 8½-in. hole section with an RSS and the 77⁄8-in. hole with conventional motor assemblies.
The first commercial HALO RSS run in a 77⁄8-in. hole run was completed in the Marcellus Shale in August 2018. The well involved a complex 3-D curve section, followed by a 1,829-m (6,000-ft) lateral section. The RSS went into the wellbore at a 60-degree inclination and completed the curve section to the lateral heel in one run.
The curve dropped and turned from 60 degrees to 23 degrees, then built and turned from the 23- to 90-degree inclination, all on a 9-degree DLS plan. To execute the 9-degree DLS curve, the HALO RSS utilized about 62.5% of its potential DLS output. The system is capable of 15-degree DLS max, placing it at the high end of the market regarding curve drilling capability.
The lateral section was then drilled with directional placement using Scientific Drilling’s drilling control algorithms, enabling the downhole HALO system to automatically control not only its inclination but also its azimuth, allowing the RSS to follow the well plan with minimal operator input and deliver better than expected results.
Fewer drilling interruptions
The RSS is controlled by commands based on a combination of stepped and variable time-based flow changes that are sent using standard rig pumps. The majority of these are sent while drilling ahead, and full up-hole telemetry decoding is maintained during the downlink. Once a command is sent, the downhole tool sends a confirmation message to the surface system acknowledging a successful change in directional control parameters.
For a Marcellus operator, only two downlinks were sent for azimuth placement throughout the lateral. All other downlink data were target inclination changes to maintain true vertical depth (TVD) control within the pay zone, as defined by the operations geologist. The lateral was placed 100% within the target zone. All downlinks were performed on the bottom with 98% accepted on the first communication attempt.
The HALO RSS utilizes advanced real-time control algorithms downhole to automate wellbore placement. While most RSS tools on the market can control inclination, and therefore TVD placement with tight tolerances, the HALO RSS automatically controls azimuth to the same degree of accuracy.
Improved hole quality
Over the last few years, the U.S. drilling industry has realized staggering efficiency improvements, resulting in significantly reduced drilling times compared with only a couple of years ago. Driven by these improvements, operators are more focused on the quality of the delivered wellbore, regarding proximity to plan and reduced tortuosity in the lateral section.
The HALO RSS automatically controls the wellbore trajectory using a navigational sensor package located 1.8 m (6 ft) behind the bit. The navigation package contains sensors to provide inclination and azimuth measurements.
Continually correcting the trajectory so close to the bit means that the well path is not allowed to deviate from the target settings. This means the HALO system only has to counter the natural formation tendencies, not any additional curvature established by poor directional control. The results from the enhanced control algorithms have been consistent across multiple basins and represent a step change in directional control and wellbore placement.
The company is working with operators throughout the Permian Basin, Stack and Marcellus shale plays to drill additional 77⁄8-in. holes. These wells are a combination of lateral only and curve/lateral applications. All will be motor-assisted, which is practically a standard requirement for all U.S. land work. Motor-assisted drilling allows the system to operate at a maximum bit speed of up to 350 rpm, maximizing ROP performance and reducing rig time and trips.
An annular pressure sensor will be incorporated into the steering unit, which will enable real-time equivalent circulating density calculations, further enhancing the system’s ability to execute extended-reach directional wells successfully. The HALO 500 system, for 6-in. to 6¾-in. hole sizes, entered engineering testing in the fourth quarter of 2018 while field testing is expected to take place in the mid- to late first quarter this year.