Cross Well Survey Clock Synchronization for Seismic Velocity Calibration
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Solution Overview
Problem
Current methods for building and calibrating seismic velocity models are limited by high costs, impracticality in rugged terrain, and incomplete data due to velocity inversions, which hinder accurate microseismic event detection and fracture monitoring in well stimulation and production processes.
Innovation Solution
A cross well survey system that synchronizes clocks between a seismic source in one well and a receiver in another, allowing precise timing of seismic events to improve the accuracy of velocity model calibration and microseismic event location by referencing clocks to a common reference time frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If walkaway vertical seismic profile (VSP) measurements are used to determine velocity anisotropy, then the amount and nature of velocity anisotropy can be determined, but the measurements are too costly and impractical for rugged terrain
Solution Approach 1:
The invention divides the seismic survey into two separate wells - a source well and a monitoring well - allowing independent optimization of each well's equipment and operations. This segmentation enables the use of simpler, less expensive equipment in each well while achieving the same measurement objectives as complex VSP measurements
Solution Approach 2:
The invention introduces a common reference time frame as an intermediary that synchronizes timing between the source well and monitoring well. This intermediary enables precise relative timing measurements without requiring complex coordinated operations, reducing both cost and operational complexity
2Loss of information
If walkaway vertical seismic profile (VSP) measurements are used to determine velocity anisotropy, then complete picture of anisotropy can be obtained, but the measurements are impractical for rugged terrain
Solution Approach 1:
By separating the source and receiver into different wells, the invention eliminates the need for complex surface operations required by VSP measurements, making the survey practical for rugged terrain while maintaining data completeness through precise timing synchronization
3Measurement precision
If velocity inversions in the subsurface are present, then arrival angles are limited, but this does not give a complete picture of the anisotropy present in the subsurface
Solution Approach 1:
The invention transitions from single-well vertical measurements to cross-well horizontal measurements, adding a spatial dimension that allows seismic waves to traverse the formation from different angles, thereby overcoming the arrival angle limitations imposed by velocity inversions
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 enhances the accuracy of seismic event location and velocity model calibration, overcoming traditional challenges in estimating formation shear velocity and anisotropy, especially in complex geological formations, thereby supporting more effective well stimulation and production planning.
Implementation Method 1
a seismic source in a first well and a seismic receiver in the second well to detect a seismic event that is caused by the source
Data Source
AI summary
A technique includes providing a source in a first well and a seismic receiver in a second well to detect a seismic event that is caused by the source. The technique includes referencing clocks in the source and receiver to a common reference time frame and determining a time in the reference time frame at which the seismic source generates the seismic event.