MWD Transient EM Data Inversion Using Arbitrary Pulse Lookup Tables
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Solution Overview
Problem
Existing methods for estimating subsurface formation properties using resistivity measurements from induced electrical pulses are limited by reliance on step-function excitation pulses and heuristic relationships, which are not always valid, leading to inaccurate or unreasonable inference models.
Innovation Solution
A method and system employing a lookup table-based inversion algorithm that uses a step-function excitation pulse shape to estimate formation properties by calculating a residual norm, with the ability to correct for non-step pulse shapes and incorporate prior knowledge to reject unreasonable models, thereby improving accuracy and robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If step-function excitation pulses are used for inversion, then the inversion process is simplified, but the accuracy of formation property estimation deteriorates when the actual pulse shape differs from step-function
Solution Approach 1:
The patent transforms the inversion problem by changing the parameter representation - instead of inverting for formation properties directly from arbitrary pulse data, it inverts using step-function lookup tables and then applies pulse shape correction factors. This allows the use of simplified step-function-based inversion algorithms while maintaining accuracy for arbitrary pulse shapes through the correction step.
Solution Approach 2:
The patent introduces an intermediary approach by using step-function excitation lookup tables as a intermediate step. The actual arbitrary pulse shape inversion is mediated through the step-function inversion process, which is then corrected to account for the difference between step-function and actual pulse shapes. This intermediary method simplifies the overall process while maintaining accuracy.
2Productivity
If heuristic relationships are used to infer formation properties, then the inversion process is faster, but the reliability of the inferred models deteriorates when heuristics are not valid
Solution Approach 1:
The patent changes the inversion approach from heuristic parameter relationships to a systematic lookup table-based method. Instead of relying on heuristic relationships between parameters, it uses pre-computed lookup tables from step-function inversions and applies correction factors, providing a more reliable and systematic approach that maintains processing efficiency.
Solution Approach 2:
The patent performs preliminary action by pre-computing the step-function excitation lookup tables before the actual inversion process. This pre-computation stores the results of complex inversions in advance, allowing the actual field inversion to proceed quickly by simply looking up pre-computed values and applying corrections, rather than performing full inversions in real-time.
3Measurement precision
If lookup tables based on step-function pulses are used, then inversion accuracy for arbitrary pulse shapes improves, but the need for pulse shape correction increases computational complexity
Solution Approach 1:
The patent manages the computational complexity by changing the approach to pulse shape correction - rather than performing full re-inversions for arbitrary pulse shapes, it applies correction factors to the step-function inversion results. This parameter change in the correction methodology maintains accuracy while controlling computational requirements.
Solution Approach 2:
The patent applies partial action by using only the necessary correction step rather than performing complete re-inversions. The correction approach applies just enough additional processing to account for pulse shape differences without repeating the entire inversion process, achieving accuracy improvement with minimal additional computational burden.
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
The approach provides more accurate and robust estimation of subsurface formation properties by using a lookup table-based inversion method that corrects for non-step pulse shapes and incorporates prior knowledge, reducing uncertainties and improving the reliability of the results.
Implementation Method 1
transmitting an excitation current pulse into the formation; receiving an induced pulse
Data Source
AI summary
A system and method of estimating properties of a subsurface formation are described. The method includes transmitting an excitation current pulse into the formation, receiving an induced pulse used to generate input data, and performing an inversion on the input data using a lookup table based on a shape of the excitation current pulse to estimate the properties of the subsurface formation.