Borehole Imaging Tool Grooved Sensor Pads for Anisotropy Detection
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Solution Overview
Problem
Existing borehole resistivity logging tools, such as galvanic and laterolog tools, have limited sensitivity to vertical resistivity and anisotropy, particularly in low dip conditions, making it difficult to accurately image thin formation layers and detect anisotropy in geological formations.
Innovation Solution
The use of borehole imaging tools with elongated sensing surfaces and toroids, embedded in conductive pads with grooves, that measure formation impedance by applying voltage or current between a conductive body and a return electrode, and track the position and orientation to derive detailed resistivity images of the borehole wall, enhancing sensitivity to anisotropy and dip angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional galvanic or laterolog tools are used for resistivity logging, then general formation composition indication is obtained, but sensitivity to vertical resistivity and anisotropy is limited
Solution Approach 1:
The tool divides the measurement function into multiple specialized electrode arrays, each optimized for specific measurement modes (vertical resistivity, horizontal resistivity, anisotropy detection). This segmentation allows each array to excel at its specific function rather than a single array attempting to do everything, thereby improving overall measurement precision for anisotropy and vertical resistivity.
Solution Approach 2:
The invention introduces multiple measurement dimensions by deploying electrode arrays at different orientations and positions within the tool. This includes vertical arrays for vertical resistivity, horizontal arrays for horizontal resistivity, and specifically oriented arrays for detecting anisotropy. By measuring in multiple dimensional orientations simultaneously, the tool captures comprehensive formation properties that single-dimension tools miss, particularly in low dip conditions.
2Measurement precision
If electrical currents are injected from a single location into the formation, then apparent resistivity is measured, but detailed imaging of thin formation layers is difficult
Solution Approach 1:
The tool segments the formation imaging task by using multiple electrode arrays positioned at different locations and orientations. Each array captures a specific portion of the formation's electrical properties, and the combined data from all arrays creates a detailed composite image. This segmentation enables resolution of thin formation layers that would be indistinguishable with a single electrode location.
Solution Approach 2:
The invention merges data from multiple electrode arrays with different measurement configurations into a unified formation image. By combining vertical resistivity measurements, horizontal resistivity measurements, and anisotropy measurements from various arrays, the system creates a comprehensive detailed image of thin formation layers that leverages the strengths of each measurement type.
3Measurement precision
If conventional resistivity logging is performed, then general formation evaluation is achieved, but accurate detection of anisotropy in thin layered formations is limited
Solution Approach 1:
The tool employs electrode arrays with specific local qualities optimized for detecting anisotropy. The arrays are positioned and oriented to maximize sensitivity to the specific measurement target (vertical resistivity, horizontal resistivity, or anisotropy). This local optimization of measurement geometry allows accurate detection of anisotropy in thin layered formations, as each array is specifically configured for its measurement function.
Solution Approach 2:
The system dynamically adapts its measurement strategy by using multiple electrode arrays that can detect different formation conditions. The arrays are designed to be sensitive to varying dip angles and formation geometries, allowing the tool to adapt to different geological scenarios. This dynamic capability enhances versatility in detecting anisotropy across a range of dipping formation conditions.
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 improves the detection of anisotropy in thin layered formations and increases sensitivity to dipping formations, providing more accurate resistivity images and aiding in the identification of hydrocarbon reservoirs.
Implementation Method 1
each elongated sensing surface having a corresponding toroid seated in the one or more grooves defining that elongated sensing surface. The toroid measures a current flowing through the elongated sensing surface
Data Source
AI summary
Disclosed embodiments include various borehole imaging tools and methods to provide sensing surface configurations for improving the assessment of anisotropy in layered formations. In at least some embodiments, the borehole imaging tools employ a unitary conductive body to provide a wall-contacting face with grooves that define multiple elongated sensing surfaces. This wall-contacting face can be provided on an extendable sensor pad of a wireline logging tool or embedded on the outer surface of a LWD stabilizer fin. Toroids may be seated in the grooves around each elongated sensing surface for measuring the current flow through each sensing surface. The elongated sensing surfaces can be arranged in pairs as a series of rectangular-shaped grooves that are aligned perpendicularly to each other within each of the pairs to improve detection of anisotropy in thin layered formations and improve the sensitivity to dipping in anisotropic formations.