New Inertial Steering Mode of Point-the-Bit RSS Expands Tool Operational Envelope

Hussain, Sajjad (Schlumberger) | Li, Fei (Schlumberger) | Rana, Vikram (Schlumberger) | Sharma, Varun (Schlumberger) | Dhaher, Karam Sulaiman (Schlumberger) | Blackburn, Jason (Schlumberger) | Haaland, Sigurd (Statoil ASA) | Sivertsen, Atle (Statoil ASA) | Eshraghi, Daniel (Statoil ASA) | Dashtpour, Reza (Statoil ASA) | Lunkad, Siddhartha (Statoil ASA) | Hongdul, Thanong (Statoil ASA) | Bairwa, Girish Kumar (Statoil ASA)



The point-the-bit rotary steerable system (RSS) is frequently used for high-profile directional drilling jobs in challenging environments that require high degree of directional control.

To achieve toolface control, the point-the-bit RSS control system requires two inputs: the rotation rate of the collar (CRPM) and the toolface orientation of the bit shaft. Previously, the tool utilized magnetic field measurements to compute the above two parameters and, subsequently, control the toolface for the well trajectory. However, the point-the-bit RSS steerability is compromised in a blind zone (where magnetic field measurement is significantly interfered with, such as inside casing, drilling out of a whipstock window, or close to offset wells, or does not have enough signal strength, such as in a zone of exclusion (ZOE) where the Earth's magnetic field projection on the cross section of tool is low. The new inertial steering mode of the point-the-bit RSS uses accelerometers and a rate gyroscope sensor to steer the tool, and it can be toggled on or off by a mud downlink. This inertial steering mode effectively expands the operational envelope of the point-the-bit RSS by improving tool steering ability when the tool is in a blind zone or ZOE.

Four successful field runs have been completed on one of the largest mature fields in North Sea Continental Shelf (NCS). In the first field run, the new inertial steering mode of the point-the-bit RSS was used to kick off a well, which is close to seven nearby producing wells, from an openhole cement plug through a 37-m narrow window between the 20-in. casing shoe and 13 3/8-in. casing stump and to drill a 17 ½-in. section in the same run. The new inertial steering mode helped to steer in the desired direction with good tool face control in the presence of high magnetic interference. In the second field run, the RSS tool successfully exited the whipstock window and steered in the desired direction using the new inertial steering mode, providing planned separation from the cuttings re-injection (CRI) zone and drilling the 12 ¼-in. section to target depth (TD). In the third field run, the new inertial steering mode was deployed to exit the whipstock window, drill the 8 ½-in. section to TD, and land on top of the reservoir close to five offset wells with a minimum 14-m center–to-center distance. The fourth field run helped the operator to exit whipstock window inside the 13 3/8-in. casing and steer the 12 ¼-in. section underneath motherbore in a high magnetic interference and collision risks environment.

Based on the four successful runs, the new inertial steering mode of the point-the-bit RSS has been proven for its tool face and trajectory control, expanding the tool's operational envelope.