Real-time communication of rotary steerable system (RSS) measurements and status to surface is critical for optimizing drilling performance and staying on target. In most North American land drilling rigs that utilize RSS, the measurement-while-drilling (MWD) tool and RSS are separate systems without a direct communication link. Instead, short-hop communication systems are used to bridge the gap between the RSS and the MWD. Short hops typically send data over short distances of 10 to 30 ft and utilize wireless communication techniques.
The two most common short-hop technologies are electromagnetic (EM) and magnetic. EM short hops utilize gap subs, which provide an insulating gap in the bottomhole assembly (BHA) across which a voltage can be applied. The transmitter applies a voltage across its gap, and current flows through the drilling fluid and formation.
The receiver then measures the corresponding voltage across its gap and decodes the signal. Both the transmitter and the receiver in an EM short hop require a gap sub.
Gap subs are typically constructed using an insulating epoxy or ceramic section between two halves of a drilling sub, electrically isolating what is above from what is below. This technology has its shortcomings, because they can fail, resulting in a lost-in-hole event that can cost upward of $1 million. Gap sub reliability has increased over the years, but gap sub failures still occur.
Magnetic short hops communicate by transmitting and receiving magnetic fields directly, which does not require gap subs. A magnetic transmitter typically consists of a coil or solenoid driven by a transmitter electronics assembly that creates a time-varying magnetic field.
This magnetic field passes through the nonmagnetic drilling collars and is received in the MWD by magnetometers or a receiving coil. Magnetic short hops typically have less range than EM short hops, but their primary advantage is that they do not require gap subs in the BHA. Another advantage of magnetic short hops is that they are not affected by drilling-fluid conductivity or formation resistivity.
Operational Challenges
One of the primary reasons short-hop systems are needed is that the majority of MWD systems used in North America utilize bottom-mounted positive mud pulsers to transmit mud-pulse telemetry to surface. Bottom-mounted pulsers have been proven and refined for decades. They are also economical to operate and reliable.
It is very difficult and impractical to get a wired connection through the bottom-mounted pulser assembly all the way from the RSS to the MWD, thus necessitating a short-hop communication system to get data from the RSS to the MWD when bottom-mounted pulsers are used.
MWD systems that utilize top-mounted pulsers can connect directly to the RSS and do not typically require a short-hop communication system. However, top-mounted pulsers are more expensive to maintain, and their reliability is typically lower than that of modern bottom-mounted pulsers.
One of the largest challenges with magnetic short-hop systems is that magnetic field strength decreases approximately with the cube of the distance from the source. Generating a magnetic field strong enough to detect even 10 to 15 ft away with the power available downhole is one challenge.
The corresponding challenge on the receiving side is having magnetometers that are sensitive enough to detect and decode the magnetic signal at those distances. A key factor in enabling a magnetic antenna or the magnetometers in the magnetic receiver to decode a signal at that distance is having a sufficiently low noise floor in the receiving circuitry and in the sensors or antennas themselves.
Another factor that affects the performance of magnetic short-hop communication systems is that, under vibration and drilling conditions, the alignment between the transmitter and the receiver can change due to drilling dynamics. This variation in the angle between the transmitter and receiver, caused by shock and vibration downhole, translates to corresponding noise in the magnetic receiver system.
Magnetic Short-Hop System Overview
The magnetic short-hop system is connected directly on top of the RSS, with a hard-wired electrical connection to the RSS. The short hop is powered from the RSS turbine and receives measurements, parameters, and status information from the RSS over its hard-wired connection. It then encodes those RSS measurements and transmits them over the magnetic link.
The magnetic short-hop system uses specialized interfaces to communicate with the RSS and has an electrical power-amplifier stage that it uses to drive a large magnetic solenoid, which generates the magnetic signal to the MWD. The transmitter electronics are all probe-based, housed in 1⅞-in. pressure housings and can easily adapt to varying collar sizes.
The receiver is likewise housed in a standard 1⅞-in. MWD pressure housing, which is simply a 16-in.-long electronics module installed in the MWD system directly above the pulser electronics. The magnetic receiver is based on the field-proven technology called a MicroPulse directional module, with more than 1.5 million circulating hours, which utilizes silicon-based magnetometers that have a very low noise floor and have been used successfully in magnetic ranging applications.
Minimizing the impact of shock and vibration on decoding of the received magnetic signal proved to be quite a challenge under rotation rates of 300 rotations per minute (RMS) and above and vibration levels ranging from 5 to 10 g root mean square, which is considered typical.
The magnetic receiver uses multi-axis magnetometers, allowing magnetometer axes that are orthogonal to the primary sensing axis to help reduce and cancel uncorrelated noise from the system. This significantly increased the signal-to-noise ratio of the receiver under drilling vibration, enabling reliable decoding of the magnetic signal under real-world drilling conditions.
The magnetic short-hop system allows users to complete a communication test on bank (prior to BHA pickup) in 10 minutes and, once the BHA is assembled, a rig-floor communication test in an additional 10 minutes.
This rig-floor test enables the operator to quickly verify successful communication without requiring additional test hardware or jumper cables, which are typically needed for EM short-hop systems. Because the system does not require gap subs, it also removes the torque limitations associated with those components during extended lateral drilling.
Field Test Results
MagLink entered field testing in November 2025 and has completed more than 35 runs to date and drilled over 249,000 ft, continuing to provide reliable communication under a wide variety of drilling conditions. Initial versions of the system did not support testing communication on the rig floor, as the first iterations of the receiver hardware were saturated by the strong magnetic fields on the rig.
The second-generation receiver, which is now widely deployed, resolved this issue, enabling a quick and convenient rig-floor test of the complete system and validating data transmission from the RSS to the surface decoder prior to tripping to bottom.
Fig. 1 shows data from a run plotting signal-to-noise ratio (SNR) vs. vibration level in g RMS. These data indicate that SNR is only minimally affected as vibration increases.
One mid-sized independent operator recently completed two back-to-back curve-and-lateral runs, with a combined length of 22,220 ft using this magnetic short-hop system. Across those runs, 99.7% of the data from the RSS was successfully transmitted to the MWD, with zero reported communication interruptions at surface.
Even when a small portion of the data is not received during a given transmission sequence, 0.3% in this case, the information is transmitted multiple times across the link, allowing drilling operations to continue uninterrupted.
Of the 36 runs completed to date, 31 have been in the Uinta Basin, three in the Permian Basin, one in the Eagle Ford Shale, and one in the Powder River Basin.
Upcoming deployments are expected to further expand the system’s use in these basins, with new deployments also planned in Oklahoma. To date, all runs have been with oil-based mud, and no significant variation in performance has been observed among the different basins.
Operators that have used this short-hop communication system have ranged from mid‑sized independents to large independents, with most deployments to date occurring with mid‑sized independents.
A recent run in the Powder River Basin with a large independent operator set a new record for that operator in that basin with 22,051 ft drilled in a one-run curve lateral with the magnetic short-hop system with continuous real-time communication from RSS to MWD. The run started at a measured depth of 6,561 ft and was drilled to a depth of 28,612 ft over 7 days.
Conclusion
Magnetic short-hop systems eliminate a key BHA failure mode associated with EM short hops: mechanical failure of the gap subs, which can lead to a very costly lost-in-hole event. The magnetic short-hop system has demonstrated reliable magnetic communication and increased BHA integrity, enabling operators to drill harder and farther. JPT
David Erdos, SPE, is a product line manager at Erdos Miller focused on downhole electronics and magnetic ranging systems for drilling applications. He has more than 15 years in systems engineering, mixed-signal circuit design, embedded systems, and high-temperature electronics for oilfield tools. In his current role, he leads development of magnetic ranging technologies, directional sensors, and short hop systems for oil and gas and geothermal wells.
Erdos joined Erdos Miller as a design engineer and began his career with Boeing Commercial Airplanes, focusing on wireless networks and power-line communications. He holds an MSc in electrical engineering from the Technion at the Israel Institute of Technology and a BS from Missouri University of Science & Technology.
