Anisotropic Distance Calculation Using Angular Velocity
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Solution Overview
Problem
Current methods for imaging subterranean rock layers fail to accurately determine the distance to boundaries due to anisotropic properties, leading to errors in well placement and resource extraction, as they do not adequately compensate for velocity variations caused by anisotropy in rock layers.
Innovation Solution
The method involves transmitting signals from a borehole transmitter and receiving them at multiple locations, calculating the distance to a rock layer boundary by compensating for anisotropy based on time periods and signal velocities, using equations that account for the angle of propagation and effective anisotropic signal velocity to model the distance accurately.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If signal velocity is assumed constant for distance calculation, then calculation process is simple, but measurement precision deteriorates due to anisotropic velocity variations
Solution Approach 1:
The patent changes the velocity parameter from a constant value to an angle-dependent variable velocity model that accounts for anisotropic properties. The velocity is expressed as a function of propagation angle relative to the bedding plane, allowing accurate distance calculation in anisotropic formations while maintaining a systematic calculation approach.
Solution Approach 2:
The patent introduces an angular dimension to the velocity parameter, transforming it from a scalar constant to a function that varies with propagation direction. This dimensional addition allows the system to account for anisotropic effects by considering the angle between the signal propagation path and the rock layer bedding plane.
2Measurement precision
If anisotropic compensation is implemented, then measurement precision improves, but calculation complexity increases
Solution Approach 1:
The patent modifies the velocity parameter to include angular dependence, transforming it from a constant to a variable that changes with propagation direction. This allows accurate compensation for anisotropic effects by adjusting velocity based on the angle between the signal path and bedding plane, thereby improving boundary distance measurement precision.
Solution Approach 2:
The patent replaces simple time-distance calculations with a more sophisticated model that incorporates angular velocity variations. By substituting the constant velocity assumption with an angle-dependent velocity function, the system achieves accurate anisotropic compensation while maintaining a systematic computational approach.
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 provides precise calculation of rock layer boundaries, reducing the risk of drilling into undesired formations and improving the efficiency of oil and gas extraction by accurately accounting for anisotropic effects on signal velocity.
Implementation Method 1
The signal emitted from the transmitter(s) propagates through the rock layer being logged, reflects and/or refracts off of a boundary of the rock layer, and is received by the receivers
Implementation Method 2
The signal emitted from the transmitter(s) propagates through the rock layer being logged, reflects and/or refracts off of a boundary of the rock layer, and is received by the receivers
Implementation Method 3
The velocity of the waveforms or signals may be affected by anisotropic properties in the logged rock layer or boundary such as faults in the rock layer, cracks in the rock layer, a change in lithology in the rock layer or a change in an unconformity within the rock layer
Data Source
AI summary
A disclosed example method includes providing, in a borehole, a transmitter (Tx) and receivers (Rxs) spaced linearly from Tx at known distances, measuring linear propagation times (LPts) for a signal to propagate from Tx to each of Rxs, determining an inline velocity (VINL) based on LPts, measuring reflection times (Rts) for a signal to propagate from Tx to each of the Rxs via a boundary, for each of Rts, providing a time-distance anisotropic velocity (TDAV) relationship depending on an effective signal velocity (ESV) in an anisotropic formation adjacent the boundary as a function of reflection angle for the reflection time signal to the boundary, VINL and orthogonal velocity, performing semblance processing to combine the TDAV relationships with VINL for a best-fit calculation of the ESVs for the different reflection angles of the reflection time signals, and calculating a distance for the corresponding receiver to the boundary on the calculation.