Anisotropic Formation Resistivity Inversion for Saturation Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for determining resistivity and dielectric constant in subterranean formations, particularly anisotropic sedimentary formations, yield unstable and erroneous results due to insufficient consideration of the sensitivity difference between horizontal and vertical conductivities, leading to errors in water/hydrocarbon saturation calculations.
Innovation Solution
A method utilizing full-wave pixel inversion with a one-dimensional formation model and regularization techniques to simultaneously determine vertical and horizontal resistivity and dielectric constant values, accounting for anisotropy and layering in electromagnetic propagation measurements, using electromagnetic propagation tools with triaxial antenna configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electromagnetic propagation measurements are processed using isotropic formation models, then processing simplicity is maintained, but measurement precision deteriorates due to inability to accurately determine resistivity and dielectric constant in anisotropic formations
Solution Approach 1:
The patent transforms the formation model from a simple isotropic single-parameter model to an anisotropic multi-parameter model that accounts for different horizontal and vertical resistivity and dielectric constant values. This parameter expansion enables accurate characterization of clay-bearing sedimentary formations while maintaining processing feasibility through systematic inversion algorithms.
Solution Approach 2:
The patent introduces an additional dimension of anisotropy by treating horizontal and vertical conductivities as distinct parameters rather than assuming uniform conductivity in all directions. This dimensional expansion in the formation model allows accurate representation of layered sedimentary structures and improves measurement precision for anisotropic formations.
2Reliability
If isotropic formation models are used for processing, then processing ease is maintained, but reliability deteriorates due to unstable and erroneous dielectric constant values in anisotropic formations
Solution Approach 1:
The patent changes the fundamental parameters of the formation model to include separate horizontal and vertical dielectric constant values, enabling reliable determination of dielectric properties in anisotropic formations. This parameter differentiation resolves the instability and errors associated with isotropic model assumptions.
Solution Approach 2:
The patent implements an iterative inversion process that uses feedback from measured electromagnetic propagation data to continuously refine the estimated formation parameters. This feedback mechanism ensures convergence to stable and reliable solutions while accounting for the complexity of anisotropic formation structures.
3Measurement precision
If electromagnetic propagation measurements are made in clay bearing sedimentary formations, then comprehensive formation information is obtained, but measurement precision deteriorates due to large dielectric constant effects that interfere with resistivity determination
Solution Approach 1:
The patent merges the determination of resistivity and dielectric constant into a unified inversion process that simultaneously solves for both parameters. By combining these measurements and processing them together using the anisotropic formation model, the harmful interference of large dielectric constant effects is eliminated, and accurate resistivity values are obtained even in clay-bearing formations.
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
Provides accurate and robust estimates of anisotropic resistivity and dielectric constant values, free from bed boundary and dipping effects, enabling precise water/hydrocarbon saturation estimation and reducing measurement noise, applicable to both wireline and logging while drilling operations.
Implementation Method 1
transmitting electromagnetic energy into the surrounding environment (including the formation)
Implementation Method 2
Electromagnetic propagation measurements are primarily used to determine resistivity and resistivity anisotropy of subterranean reservoirs
Data Source
AI summary
A method for estimating vertical and horizontal resistivity values and vertical and horizontal dielectric constant values of a multi-layer, anisotropic subterranean formation includes acquiring electromagnetic propagation measurements of the subterranean formation and inverting the measurements using a one-dimensional formation model to compute the anisotropic resistivity and anisotropic dielectric constant values. The model includes a plurality of formation layers in which each of the formation layers has corresponding vertical and horizontal real conductivity and vertical and horizontal imaginary conductivity values.