Measurement-While-Drilling Surveying of Near-Vertical Wells and in Sections of Multi-Well Structure Using FOG-based INS

Aboelmagd Noureldin, Herb Tabler, Dave Irvine-Halliday and Martin P. Mintchev

Abstract:	Fiber optic gyroscopes (FOG) have been suggested as a replacement for magnetometers in measurement-while-drilling (MWD) surveying of horizontal wells. It has been shown that a single FOG with its sensitive axis normal to the tool spin axis can be incorporated together with three-axis accelerometers to survey highly-inclined/horizontal well sections. However, this methodology does not address the issue of azimuth monitoring in near-vertical wells. Moreover, when drilling several wells from an offshore platform, the azimuth direction is critical to avoid collision with nearby wells. Therefore, it will be very beneficial if the FOG technology can be applied to accurately monitor the azimuth when the drill pipe starts to deviate from the vertical direction but prior to reaching highly-inclined/horizontal sections. This study employs the FOG technology to continuously monitor the azimuth in near-vertical wells and to prevent collisions with adjacent wells. Due to its compactness and environmental insensitivity, the FOG can be installed inside the bearing assembly directly behind the drill bit with its sensitive axis aligned along the tool spin axis. The FOG is integrated with three-axis accelerometers to determine the azimuth and the inclination angles as well as the position of the bottom hole assembly (BHA). This system employs the accelerometer measurements to continuously provide two synthetic rotation rate components in two mutually orthogonal directions normal to the tool spin axis. On the other hand, the FOG monitors the rotation rate along the tool spin axis. These rotation rate components are combined with the accelerometer measurements to provide continuous MWD surveying. An error state model is developed to describe the error behavior of this MWD surveying technique. Optimal estimation of these error states is based on conventional Kalman filtering methods employing the length of the drill pipe and the BHA penetration rate for measurement updates. In experimental models of wells deviating from the vertical by up to 20 o , the proposed system determined the azimuth and the inclination with errors less than 1%. The FOG-based system improves the surveying accuracy in near-vertical wells and prevents collisions in multi-well structures.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	193 - 204
Cite this article:	Noureldin, Aboelmagd, Tabler, Herb, Irvine-Halliday, Dave, Mintchev, Martin P., "Measurement-While-Drilling Surveying of Near-Vertical Wells and in Sections of Multi-Well Structure Using FOG-based INS," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 193-204.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In