Two-Way Check Shot Seismic Measurement Without Clock Sync
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Solution Overview
Problem
Current borehole seismic measurements are inaccurate at depth, leading to distorted oil reservoir mapping and costly drilling errors, due to limitations in traditional wireline-based methods that require synchronized clocks and face bandwidth constraints, resulting in operational difficulties and high costs.
Innovation Solution
A method that uses a surface seismic source and downhole receivers to measure seismic energy, with a downhole seismic source activated after detecting the surface source, allowing for independent time measurements and eliminating the need for clock synchronization, and utilizing mud pulse telemetry to transmit delay intervals, enabling accurate velocity measurements without interfering with drilling processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wireline-based borehole seismic measurements are used, then seismic velocity measurement is possible, but the method requires synchronized clocks and faces bandwidth constraints, resulting in operational difficulties and high costs
Solution Approach 1:
The patent extracts the clock synchronization requirement from the measurement system by using independent clocks at surface and downhole that do not need to be synchronized. The system measures two-way travel time without requiring the clocks to be synchronized, thereby eliminating the complex synchronization infrastructure while maintaining measurement capability
Solution Approach 2:
The patent inverts the traditional one-way measurement approach by implementing a two-way measurement system where seismic energy travels from surface to downhole and back. This inversion allows independent clock operation because the measurement captures the round-trip time directly, eliminating the need for synchronized timing references
2Measurement precision
If traditional wireline-based borehole seismic measurements are used, then velocity measurement can be obtained, but it requires significant rig time and interferes with drilling processes
Solution Approach 1:
The patent implements a dynamic measurement system that can be performed quickly during drilling operations without requiring the drill to stop. The system adapts to the drilling process by using the existing drill string as the measurement conduit, allowing continuous operation and eliminating the need for separate wireline intervention trips
Solution Approach 2:
The patent makes the drill string serve multiple functions: both as the drilling tool and as the conduit for seismic energy transmission and telemetry. This multi-functionality eliminates the need for separate wireline equipment and operations, allowing velocity measurements to be obtained during normal drilling without additional rig time or interference
3Measurement precision
If highly accurate clocks are used for synchronization, then timing precision is improved, but the clocks are expensive to build and maintain
Solution Approach 1:
The patent replaces expensive, highly accurate synchronized clocks with inexpensive independent clocks at surface and downhole. The system accepts that these clocks may drift but compensates through the two-way measurement approach, thereby eliminating the need for costly precision timing equipment while maintaining sufficient measurement accuracy
4Measurement precision
If downhole receivers are used with surface seismic source, then velocity measurement is possible, but the limited bandwidth of communication from borehole to surface makes data transmission challenging
Solution Approach 1:
The patent inverts the communication direction by transmitting telemetry data from surface to downhole rather than from downhole to surface. The downhole receiver records the time of receiving the seismic signal and stores it locally, then transmits the pre-recorded data upward when the opportunity arises, thereby bypassing the limited downhole-to-surface bandwidth constraint
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 accurate seismic velocity measurements at depth, reduces operational complexities, and allows for flexible data acquisition, improving the accuracy and efficiency of oil exploration by refining seismic maps and reducing capital waste.
Implementation Method 1
Seismic energy is transmitted into the earth using a surface seismic source located on the surface of the earth. The seismic energy from the surface seismic source is received with one or more downhole receivers located in a borehole.
Implementation Method 2
In response to the received seismic energy from the surface seismic source, seismic energy is transmitted into the earth using a downhole seismic source located in a borehole. The seismic energy from the downhole seismic source is then received with one or more surface receivers located on the surface of the earth.
Implementation Method 3
The measured delay interval is transmitted to the surface
Data Source
AI summary
Methods and related systems are described making seismic measurements. Seismic energy is transmitted into the earth using a surface seismic source. The seismic energy is received with one or more downhole receivers located in a borehole. In response to the received seismic energy from the surface seismic source, seismic energy is transmitted into the earth using a downhole seismic source. The seismic energy from the downhole seismic source is then received with one or more surface receivers located on the surface of the earth. A delay interval is measured downhole between the first arrival of the seismic energy from the surface seismic source and the transmission from the downhole seismic source. A surface interval is measured between the transmitting of seismic energy from the surface seismic source and first arrival of the seismic energy from the downhole seismic source using the one or more surface receivers. Travel time can be calculated by subtracting the delay interval from the surface interval.