Pixelated Resistivity Inversion for Formation Boundary Identification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional resistivity logging tools face challenges in accurately determining formation boundaries and characterizing subsurface formations due to computational complexity and ambiguity in inversion algorithm solutions, especially in formations with high contrast between resistive and conductive layers, which affects geosteering and hydrocarbon resource extraction.
Innovation Solution
The implementation of a distance-to-bed-boundary (DTBB) inversion algorithm and ensemble statistics analysis to filter convergent solutions, pixelate data, and generate composite resistivity statistics, allowing for improved boundary identification and formation modeling, enabling more accurate geosteering and hydrocarbon resource extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a layered model-based inversion algorithm is used to identify formation boundaries, then the detection capability is improved, but computational complexity increases and solution ambiguity occurs in high contrast formations
Solution Approach 1:
The patent segments the continuous resistivity log data into discrete pixelated representations. By dividing the formation data into discrete depth intervals and radial zones, the complex continuous inversion problem is transformed into a manageable discrete pixel grid, reducing computational complexity while preserving boundary identification capability
Solution Approach 2:
The patent changes the parameter representation from continuous resistivity values to discrete pixelated solutions with associated probabilities. This parameter transformation allows the use of statistical methods (ensemble statistics, standard deviation) to quantify solution ambiguity and select the most probable formation model, resolving the contradiction between accuracy and computational complexity
2Ease of operation
If conventional resistivity logging tools are used, then the operational simplicity is maintained, but the detection range is limited to 5-10 feet with maximum 18 feet
Solution Approach 1:
The patent extends the detection capability by utilizing multiple receiver antennas at different radial distances from the wellbore. This dimensional extension from single-point to multi-radial measurement allows ultra-deep resistivity logging to detect boundaries up to 200 feet away, while the pixelated inversion methodology maintains operational simplicity by providing a unified analysis framework
3Adaptability or versatility
If multiple strata are present within detection range, then the formation complexity increases, but qualitative methods such as correlation method fail due to computational complexity
Solution Approach 1:
The patent introduces pixelated solutions as an intermediary representation between the raw resistivity data and the final formation model. This intermediate pixel grid serves as a mediator that simplifies the mathematical operations required to handle multiple strata, enabling the processing of complex multi-layer formations without excessive computational burden
Solution Approach 2:
The patent employs ensemble statistics and standard deviation calculations as feedback mechanisms to evaluate the quality and reliability of inversion solutions. By computing statistical measures across multiple candidate solutions, the system can identify the most probable formation model and detect boundaries with confidence, even in complex multi-strata environments
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 formation boundary identification and resistivity modeling, improving the ability to direct drilling operations towards hydrocarbon-rich zones by reducing ambiguity in inversion algorithm solutions and providing a more precise resistivity profile.
Implementation Method 1
one or more antennae for transmitting an electromagnetic signal into the formation. When operated at low frequencies, the resistivity tool may be called an induction tool
Data Source
AI summary
A system and method for evaluating a subterranean formation includes a logging tool that includes transmitter and receiver antennae. The transmitter antenna transmits a first electromagnetic signal into the formation at a plurality of depths. The receiver antenna receives a plurality of second electromagnetic signals emitted by the formation in response to the first signal. The system and method also include a processor configured to calculate resistivity values for the second signals, calculate solutions to an inversion algorithm of the formation, filter the solutions into a plurality of convergent solutions, pixilate the convergent solutions into pixilated solutions, calculate ensemble statistics for the pixilated solutions, calculate a difference in resistivity value between successive pixels, identify presumptive layer boundaries based on the differences in resistivity values, calculate composite resistivity statistics from the pixilated solutions based on the presumptive layer boundaries and the ensemble statistics, and generate a formation model.