Borehole Tool Position Estimation Using Rotational Acoustic Imaging
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Solution Overview
Problem
Conventional methods for determining the downhole formation evaluation tool position in a borehole during drilling lack the ability to accurately track the tool's center and orientation, leading to inadequate environmental corrections and inefficient acquisition of geometric information about the borehole, particularly for non-azimuthal tools and in cases where the tool is eccentric or centered.
Innovation Solution
A method and apparatus that use a logging string with an imager and formation evaluation sensor to estimate the borehole geometry and tool location by making rotational measurements of distance to the borehole wall, processing these measurements to correct for standoff and provide accurate formation property estimates, including a 3-D view of the borehole and identification of defects, using a least-squares fit and outlier rejection techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional eccentered or centered correction assumptions are used, then the correction process is simplified, but the measurement precision of formation evaluation is degraded due to inability to track actual tool position and orientation
Solution Approach 1:
The patent replaces mechanical position tracking systems with an acoustic field-based method. Acoustic signals are transmitted through the borehole fluid and reflected off the borehole wall to determine tool position and orientation. This substitution eliminates complex mechanical sensors while achieving precise positioning through acoustic travel time measurements and signal processing
Solution Approach 2:
The patent introduces acoustic signals as an intermediary to indirectly determine tool position and orientation. Instead of directly measuring mechanical position, the system uses acoustic wave propagation through the borehole fluid and reflection patterns as a mediator to infer tool location, achieving position tracking without direct mechanical contact or complex positioning hardware
2Productivity
If separate wireline logging runs are performed after drilling, then comprehensive formation evaluation data can be obtained, but the time and cost of the drilling process increase
Solution Approach 1:
The patent merges formation evaluation measurements with drilling operations by enabling logging-while-drilling (LWD). The formation evaluation tool is integrated into the drilling assembly, allowing simultaneous drilling and formation characterization. This combination eliminates the need for separate wireline logging runs while maintaining measurement quality through real-time data acquisition during drilling
Solution Approach 2:
The patent performs formation evaluation measurements preliminarily during the drilling process itself, before the formation is damaged by mud invasion that occurs after drilling completes. By acquiring formation data in real-time during drilling, the system obtains high-quality measurements earlier in the process, eliminating the need for subsequent wireline logging runs
3Measurement precision
If azimuthal FE tools with rotation are used, then the diluting effects of rotation may not appear, but the conventional approaches lack the ability to provide absolute standoff correction for tool location and orientation
Solution Approach 1:
The patent implements a feedback mechanism where acoustic measurements of borehole geometry and tool position are continuously obtained and used to dynamically calculate and apply standoff corrections. The system measures the actual tool position relative to the borehole center through acoustic reflections, then feeds this information back to adjust formation evaluation measurements in real-time, providing accurate absolute standoff correction without conventional assumptions
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise determination of the tool's position and orientation, improving the accuracy of formation evaluation measurements and reducing the need for separate wireline logging runs, thereby saving time and costs while enhancing the quality of data used for geo-steering and other drilling decisions.
Implementation Method 1
an imager to make rotational measurements using an imaging instrument of a distance to a wall of the borehole
Implementation Method 2
measuring an amplitude of a reflected acoustic signal from the wall of the borehole
Data Source
AI summary
Caliper measurements made during rotation of an imager on a logging string are processed to estimate the location of the imager, and size and shape of the borehole. A piecewise elliptical fitting procedure may be used. These estimates may be used to correct measurements made by a standoff-sensitive formation evaluation sensor such as a neutron porosity tool. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.