Subsurface Strain Estimation via Intermediary Well Calibration
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Solution Overview
Problem
The challenge in estimating strain along a well without direct fiber optic measurement, as the structure of a well often prevents the placement of exterior fiber optic cables, necessitating alternative methods to characterize strain and velocity-strain information.
Innovation Solution
The system employs interior fiber optic cables within the well to measure time-strain and uses fiber optic measurements from other wells to determine velocity-strain per strain values for adjacent rock types, enabling strain estimation along the well based on time-strain and velocity-strain information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exterior fiber optic cables are placed directly on the well to measure strain, then measurement precision is improved, but the well structure prevents this placement
Solution Approach 1:
The patent uses an intermediary well (calibration well) with known strain measurements to bridge the gap between the target well and the measurement system. By measuring strain in the intermediary well and using the velocity-strain relationship, the system indirectly determines strain in the target well without direct cable placement, resolving the contradiction between measurement precision and ease of operation.
Solution Approach 2:
The patent creates a mathematical model (copy) of the strain field in the target well based on measurements from the calibration well. Instead of physically placing cables in the target well, the system copies the strain characteristics from the calibration well using the velocity-strain relationship, achieving measurement precision without direct physical access.
2Loss of information
If direct fiber optic measurement is used, then strain information accuracy is improved, but the structure of the well does not allow for cable placement
Solution Approach 1:
The calibration well serves as an intermediary that provides the necessary strain information for the target well. By using the calibration well's measurements and the velocity-strain relationship as a mediator, the system recovers accurate strain information for the target well without needing to physically access its structure, thus overcoming the device complexity barrier.
Solution Approach 2:
The patent replaces the mechanical system of direct physical measurement (fiber optic cables in the target well) with a computational approach. By substituting the mechanical measurement system with a mathematical model based on velocity-strain relationships and calibration data, the system achieves accurate strain information without the complexity of direct cable placement in the target well structure.
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 accurate estimation of strain along the well, even without direct fiber optic measurement, by characterizing time-strain and velocity-strain relationships, facilitating subsurface strain forecasting and mechanical earth model calibration.
Implementation Method 1
The speed of light through the well may change based on the strain of the well. The change in the speed of light through the well may cause a time shift
Data Source
AI summary
Strain and time-strain measurement in a well enables derivation of a constant that links the two. Knowledge of the constant along with time-strain measurement at another well enables estimation of strain at the other well.