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An Iterative Method To Measure Wellbore Azimuth While Drilling

IP.com Disclosure Number: IPCOM000242104D
Publication Date: 2015-Jun-18
Document File: 9 page(s) / 215K

Publishing Venue

The IP.com Prior Art Database

Abstract

An iterative method and algorithm is presented for measuring the azimuth angle of a borehole being drilled, the data for determining the azimuth angle is acquired from a previous standard (non-rotating) survey station and from data acquired while the drill-string is under rotation.

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An Iterative Method To Measure Wellbore Azimuth While Drilling

Abstract

An iterative method and algorithm is presented for measuring the azimuth angle of a borehole being drilled, the data for determining the azimuth angle is acquired from a previous standard (non-rotating) survey station and from data acquired while the drill-string is under rotation.

Introduction

Typical logging / measuring while drilling (L/MWD) technology utilizes the measurement of the x, y, and z components of the gravitational field (G) and magnetic field (H) while the drill-string is stationary in order to determine the inclination (I) and azimuth (A) of the wellbore. With the advent or rotary closed loop steerable (RCLS) technologies and subsequently the increasing complexity in well trajectories the need for accurate real-time while drilling azimuth and inclination data has magnified.

The iterative method introduced herein utilizes the known x, and y components (of G and H) from the last stationary survey point in concert with the z components (of G and H) acquired while rotating and drilling to solve for a new set of x and y magnetometer and accelerometer values.

The iterative method treats the x and y components (of G and H while rotating) as unknowns, and uses the fact that the z components (of G and H while rotating), the total field strength (of G and H), and the dip angle (the angle between the magnetic field and the plane tangent the to the wellbores surface location) from the previous stationary survey point are known, to solve for the x and y components (of G and H while rotating). The result is a full set of tri-axial magnetometer and accelerometer data with preserved quality control measures of dip and total field strength which are then used to solve for the azimuth angle (A) while drilling. The crux of this method is that the orientation of the tools x and y measurement axis are treated as constant from the last stationary survey orientation (i.e. the "toolface" or "highside" remains the same) for the purpose of calculation of new x and y component values.

Related Work

Methods exist (Cobern et al.) to facilitate the determination of inclination and azimuth while the drill- string is being rotated, however their accuracy is limited due in part to: tool induced magnetic fields (from the internal circuitry and current flow needed to power components while drilling) which affect the measurement of the x, and y components of H while rotating, and drilling induced lateral vibrations which affect the measurement of the x, and y components of G while rotating. Additionally the method outlined by Cobern et al. requires both complex measurement and transmission of the "invariant" accelerometer and magnetometer components. The iterative method does not employ the use of any x or y data obtained while rotating and thus both measurement and transmission are unnecessary. This reduces complexity, as well as design, maintenance, and repair costs.

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