Downhole Acoustic Imaging Ahead of Drill Bit
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Solution Overview
Problem
Current drilling technologies face challenges in accurately controlling the direction of drilling due to the inability to effectively 'see ahead' of the drill bit, relying on unreliable seismic data and requiring methods to process acoustic data for real-time guidance.
Innovation Solution
A method and apparatus that utilize guided acoustic waves to determine the distance to an interface in an earth formation by conveying a logging instrument into a borehole, activating transmitters to produce guided waves, and using receivers to filter and estimate the distance based on downward and upward propagating wave signals, employing dip filtering to separate and process the signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If seismic data is used to determine the area to drill and approximate depth of pay zone, then drilling can proceed without stopping, but the reliability of the data deteriorates at great depths
Solution Approach 1:
The patent replaces seismic data (which relies on surface-based mechanical wave propagation) with acoustic wave propagation through the borehole. The acoustic waves travel through the formation material directly, providing more reliable real-time data at great depths while allowing continuous drilling operations without stopping.
Solution Approach 2:
The patent introduces acoustic waves as an intermediary medium between the drill bit and the formation interfaces. These waves propagate through the borehole and formation, carrying information about the subsurface structure back to the drilling equipment, enabling real-time imaging without requiring surface seismic data.
2Loss of information
If logging is performed on an unfinished hole prior to setting casing, then formation information can be obtained, but washouts occur that damage the drilling work already done
Solution Approach 1:
The patent replaces traditional mechanical logging methods (which require physical contact and can cause washouts) with acoustic wave propagation. The acoustic waves travel through the formation without requiring mechanical intervention, obtaining formation information while preserving the integrity of the drilling work and preventing washouts.
Solution Approach 2:
The acoustic imaging method allows continuous acquisition of formation information during the drilling process without interrupting the drilling operation or requiring subsequent re-drilling after washouts. The system provides real-time imaging data that guides drilling decisions continuously.
3Ease of operation
If acoustic waves are used to image formation structures, then real-time directional control is enabled, but the complexity of signal processing increases
Solution Approach 1:
The patent segments the signal processing into distinct functional components: wave generation, wave propagation, signal reception, dip filtering, and distance estimation. This segmentation allows each component to be optimized independently and simplifies the overall system architecture while enabling real-time directional control.
Solution Approach 2:
The patent uses dip filtering that exploits changes in wave parameters (specifically the dip angle) to separate and identify acoustic waves from other signals. By transforming the signal into the dip domain, the complex task of signal separation is simplified into a parameter-based filtering process that enables real-time operation.
4Measurement precision
If multiple receivers are used to capture downward and upward propagating waves, then measurement precision improves, but the quantity of signals to process increases
Solution Approach 1:
The patent employs asymmetric dip filtering that exploits the asymmetric propagation characteristics of downward and upward waves. By applying dip filters with specific angular ranges, the system can distinguish between waves traveling in different directions, allowing precise measurement using multiple receivers without overwhelming complexity in signal processing.
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 accurate estimation of the distance to formations ahead of the drill bit, enhancing directional control during drilling by providing reliable real-time acoustic data, reducing the need for repetitive measurements and improving drilling efficiency.
Implementation Method 1
activating at least one transmitter on the logging instrument to produce a guided acoustic wave which propagates downward to the bottom of the borehole and produces an acoustic wave in the earth formation
Implementation Method 2
receive a second signal responsive to an upward propagating guided acoustic wave resulting from reflection of the acoustic wave in the formation at an interface therein
Data Source
AI summary
The present disclosure is related to apparatuses and methods for downhole acoustic logging. The tool may be used for generating a guided borehole wave that propagates into the formation as a body wave, reflects from an interface, and is converted back into a guided borehole wave. Guided borehole waves resulting from reflection of the body wave are used to image a reflector. Methods may include processing of acoustic logging signals including: wavefield separation, auto-correlation of wavefield components, filtering using a dip filter, and estimating a distance to the reflective interface.