Downhole Bending Moment Measurement for Directional Drilling Control
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Solution Overview
Problem
Directional drilling methods face challenges in accurately determining the course of a wellbore due to assumptions of constant curvature, which can lead to significant depth errors, especially with steerable motor systems, and are affected by magnetic interference from nearby wells or casing operations.
Innovation Solution
A system and method that utilize bending moment measurement devices in downhole tools to calculate dogleg severity and well tool face angles, allowing for precise estimation of changes in inclination and azimuth, thereby improving directional control and reducing the impact of magnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the minimum curvature method is applied to calculate the course of the wellbore from survey stations, then the directional drilling operation can proceed with standard equipment, but significant depth errors occur due to local curvature variations and constant curvature assumptions
Solution Approach 1:
The patent replaces the mechanical/inertial sensing system (inclinometers and magnetometers) with a bending moment measurement system. By measuring the bending moments acting on the downhole tool and calculating the resultant bending vector, the system directly determines the wellbore curvature and orientation without relying on discrete survey points and minimum curvature assumptions, thereby eliminating depth errors while maintaining continuous drilling operation
Solution Approach 2:
The patent changes the measurement parameter from discrete angular positions (inclination and azimuth at survey points) to continuous bending moment measurements. By measuring bending moments in multiple directions and calculating the resultant bending vector components (vertical, radial, and tangential), the system achieves continuous tracking of wellbore curvature and orientation, providing precise depth measurements without the limitations of the minimum curvature method
2Device complexity
If standard directional sensors (magnetometers) are used to measure azimuth angle, then the directional drilling system can be implemented with conventional equipment, but measurement accuracy deteriorates due to magnetic interference from nearby wells or casing operations
Solution Approach 1:
The patent extracts the magnetometer from the sensing system, eliminating the source of magnetic interference vulnerability. By removing the magnetic sensing component and relying solely on bending moment measurements combined with gravitational reference, the system achieves azimuth determination that is completely immune to magnetic interference from nearby wells, casing operations, or other magnetic sources in the drilling environment
Solution Approach 2:
The patent introduces bending moment measurements as an intermediary between the physical wellbore geometry and the calculated azimuth angle. Instead of directly measuring magnetic field orientation, the system measures mechanical bending moments, processes them through mathematical relationships involving gravitational reference, and derives azimuth information that is independent of magnetic field conditions
3Ease of operation
If discrete survey points are taken after drilling one stand of pipe, then the measurement process can be simplified and equipment connection time is reduced, but directional control precision deteriorates due to large intervals between measurements
Solution Approach 1:
The patent implements continuous measurement of bending moments throughout the drilling process, eliminating the discrete sampling approach. By continuously monitoring bending moment components and calculating the resultant bending vector in real-time, the system provides continuous directional information without requiring periodic connections for survey measurements, maintaining both operational simplicity and high directional control precision
Data Source
AI summary
A system for measuring directional characteristics of a downhole tool includes: at least one bending moment (BM) measurement device disposed at a downhole component, the at least one BM measurement device configured to generate bending moment data at at least one depth in the borehole, the bending moment data including a bending vector of the downhole tool, a bending moment representing an amplitude of the bending vector, and a bending tool face (BTF) angle representing an orientation of the bending vector; and a processor in operable communication with the BM measurement device and configured to receive bending moment data from the BM measurement device, calculate a dogleg severity (DLS) from the bending moment and a well tool face (WTF) angle from the BTF angle, and calculate at least one of a change in inclination and a change in azimuth based on the DLS and the WTF angle.