Sonic Tool for Thinly Laminated Bed Evaluation
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Solution Overview
Problem
The oil and gas industry faces challenges in identifying and quantifying hydrocarbons in thinly laminated beds, known as Low Resistivity Beds (LRB), as conventional resistivity measurements often underestimate hydrocarbon reserves due to factors like conductive mud invasion and clay presence, which are beyond the vertical resolution of standard logging tools.
Innovation Solution
A formation evaluation system utilizing a sonic source and receivers aligned close to the borehole wall with a horizontal offset, measuring three types of two-way trip times to determine sonic speeds in the drilling mud and invaded zone, estimating porosity and thickness of the invaded zone using time average equations, and repeating measurements to accurately characterize layer thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional resistivity measurements are used, then measurement simplicity is maintained, but measurement precision deteriorates due to inability to resolve thinly laminated beds
Solution Approach 1:
The logging tool is segmented into multiple independent sonic receivers (first, second, and third receivers) positioned at different locations. Each receiver captures acoustic signals from different paths through the formation, enabling the system to resolve thinly laminated beds by combining data from these segmented measurement points.
Solution Approach 2:
The invention transitions from conventional single-path resistivity measurement to multi-dimensional acoustic measurement by introducing receivers at offset positions and measuring travel times along different geometric paths (direct path, reflected path, and oblique path). This dimensional expansion enables resolution of thin layers that are below the vertical resolution of standard tools.
2Measurement precision
If standard logging tools are used, then device complexity is minimized, but measurement precision deteriorates in low resistivity beds
Solution Approach 1:
The sonic logging tool performs multiple functions: it measures acoustic travel times for hydrocarbon detection, characterizes invaded zone properties, and evaluates formation porosity. By integrating these multiple measurement capabilities into a single tool configuration, the system achieves high measurement precision without proportionally increasing device complexity.
Solution Approach 2:
The invention changes the measurement parameter from electrical resistivity to acoustic travel time. This parameter change enables accurate hydrocarbon detection in low resistivity beds where conventional resistivity measurements fail, as acoustic waves are less affected by the conductive mud invasion and clay presence that plague resistivity measurements.
3Reliability
If conventional resistivity logging is used, then ease of operation is maintained, but reliability deteriorates due to mud invasion and clay effects
Solution Approach 1:
The invention replaces electrical measurement mechanisms with acoustic wave propagation mechanisms. Acoustic waves interact differently with the formation, being less sensitive to the electrical conductivity effects caused by mud invasion and clay presence. This substitution fundamentally improves reliability of hydrocarbon detection in challenging formations.
Solution Approach 2:
The system uses acoustic waves as an intermediary to indirectly probe formation properties. Instead of directly measuring electrical resistivity that is corrupted by mud and clay, the acoustic travel time measurements serve as an intermediary that can be mathematically related to formation porosity and hydrocarbon saturation, providing reliable estimates despite the presence of conductive materials.
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 allows for precise characterization of thinly laminated beds, improving the accuracy of hydrocarbon reserve estimation by overcoming the limitations of conventional logging tools and addressing the underestimation of hydrocarbon reserves in LRB.
Implementation Method 1
A formation evaluation system utilizes a sonic source and receivers aligned close to the borehole wall
Implementation Method 2
measuring three types of two-way trip times to determine sonic speeds in the drilling mud and invaded zone
Implementation Method 3
measuring three types of two-way trip times to determine sonic speeds in the drilling mud and invaded zone, estimating porosity and thickness of the invaded zone using time average equations
Data Source
AI summary
A formation evaluating system including a sonic sensor device attached to a drill string adjacent to a bit includes a sonic source and a first sonic receiver aligned adjacent to the sonic source, and a second sonic receiver aligned with a horizontal offset X. Three kind of two-way trip times are measured: from the sonic source to a) the first receiver after a reflection at the borehole wall, b) the first receiver after propagation in a layer below the borehole wall, an invaded zone, and a reflection at an interface below the borehole wall, and c) the second receiver after oblique propagations in the invaded zone and a reflection at the interface. After determining a sonic speed in the drilling mud and a sonic speed in a matrix of the invaded zone, a porosity and a thickness of the invaded zone are estimated based on a time average equation.