Surface Seismic Source and Downhole Receiver Interferometry
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Solution Overview
Problem
Current subsurface technologies in the oil and gas industry struggle to monitor real-time changes in reservoir geomechanical properties, such as seismic velocities, due to limitations in core measurements and conventional seismic imaging methods, which are not effective for in situ conditions and often interfere with ongoing field operations.
Innovation Solution
A method involving surface seismic source arrays and downhole receivers using virtual source seismic interferometry to measure inter-well seismic velocities and anisotropic properties in real time, allowing for the assessment of changes induced by oil field operations like hydraulic fracturing and steam flooding, while minimizing interference with field activities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional surface and borehole 3D seismic imaging is used, then information on acoustic and shear impedance contrast is obtained, but spatial and vertical resolution is limited and real-time monitoring is not achieved
Solution Approach 1:
The patent replaces conventional 3D seismic imaging methods with a new approach using surface seismic sources combined with downhole receivers and virtual source seismic interferometry. This substitution enables direct measurement of seismic velocities with high spatial and vertical resolution while achieving real-time monitoring capability, eliminating the weeks or months of processing time required by conventional methods
Solution Approach 2:
The patent introduces downhole receivers as an intermediary component between surface seismic sources and the reservoir formation. These receivers are deployed in observation boreholes and work in conjunction with virtual source interferometry to directly measure seismic velocities, providing high-resolution data in real-time without the processing bottlenecks of conventional surface-only seismic imaging
2Reliability
If time-lapsed conventional surface 4D seismic imaging is used, then changes in geomechanical properties can be monitored, but processing takes weeks or months and interferes with ongoing field operations
Solution Approach 1:
The patent replaces time-lapsed conventional surface 4D seismic imaging with a system using surface seismic sources and downhole receivers. This substitution reduces processing time from weeks or months to near real-time, eliminating interference with ongoing field operations while maintaining reliable monitoring of geomechanical property changes
Solution Approach 2:
The patent performs preliminary deployment of downhole receivers in observation boreholes before field operations begin. This preliminary action enables continuous real-time monitoring of geomechanical changes without requiring subsequent surface seismic acquisitions that would interfere with ongoing operations, allowing immediate detection and response to reservoir changes
3Measurement precision
If core measurements are used, then geomechanical properties can be measured, but in situ conditions are not preserved due to coring and retrieval operations
Solution Approach 1:
The patent replaces physical core measurements with a non-invasive seismic measurement system using surface sources and downhole receivers. This substitution measures seismic velocities in the reservoir formation in situ without requiring core extraction, thereby preserving in situ conditions while obtaining accurate geomechanical property data
Solution Approach 2:
The patent uses downhole receivers as intermediaries to measure seismic velocities directly in the reservoir formation. This approach eliminates the need to extract core samples, preserving in situ conditions while providing accurate geomechanical property measurements through virtual source interferometry and travel time analysis
4Measurement precision
If standard sonic logging tools are used, then seismic velocities can be measured, but measurement depth is limited to a few inches to a foot from the borehole
Solution Approach 1:
The patent replaces standard sonic logging tools with a system using surface seismic sources and downhole receivers. This substitution extends measurement depth from a few inches to a foot to several thousand feet into the reservoir formation, while maintaining accurate seismic velocity measurements through virtual source interferometry
Solution Approach 2:
The patent transitions from near-borehole measurements to far-field measurements by using surface seismic sources and downhole receivers. This dimensional change allows seismic waves to propagate through the entire reservoir formation, enabling velocity measurements at depths of thousands of feet rather than limited to the immediate borehole vicinity
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
Enables real-time monitoring of geomechanical changes, allowing for quick adjustments to oil field operations and improving the effectiveness of production techniques by providing accurate and timely data on reservoir properties.
Implementation Method 1
As the velocities of seismic waves are related to in situ geomechanical properties via rock mechanic relationships, real time measurement and monitoring of local changes in seismic velocities can yield valuable information on the geomechanical state of the reservoirs
Implementation Method 2
The seismic signals detected at the receivers in the observation wells are recorded and processed in real time on a computer using the virtual source method in seismic interferometry to obtain emulated cross-well seismic signals
Data Source
AI summary
Methods for measuring seismic velocities and for monitoring local changes in inter-well seismic velocities in real time are described. Two or more spaced-apart observation wells are provided. Seismic receiver arrays are placed in the observation wells, and a seismic source array is provided at surface locations away from the well bores and producing areas. Compression (P), vertical shear (Sv) and/or horizontal shear (Sh) seismic wave signals are generated from each element of the seismic source array, and the seismic signals arriving at the receivers in the observation wells are recorded. The virtual source method is then applied to the recorded data to compute emulated cross-well seismic signals of the virtual sources at receiver locations in one observation well propagating toward the receivers at other observation wells. Analysis of direct arrivals of emulated cross-well seismic signals can be completed to extract travel times, inter-well seismic velocities, and rock properties.