Joint Induction Pressure Inversion for Reservoir Characterization
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Solution Overview
Problem
Current methods for reservoir characterization in geological formations, particularly in complex configurations like horizontal or deviated wells, face challenges due to the complexity of invasion profiles and the dynamic nature of mud-filtrate invasion, which affects the accuracy of induction logging and formation testing interpretations.
Innovation Solution
A method that directly inverts average mud-filtrate invasion rates using electromagnetic survey data and fluid flow characteristics, allowing for a joint inversion technique that provides a more reliable interpretation of formation tests and estimates porosity and permeability without relying on complex mud-cake growth models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple invasion model (step-profile three-parameter model) is used for inversion, then the inversion process is simplified and computation is faster, but the accuracy deteriorates in complex reservoir configurations like horizontal or deviated wells
Solution Approach 1:
The patent applies dynamics by transitioning from a static, simplified invasion model to a dynamic, physics-based multi-phase fluid flow model that adapts to complex reservoir configurations. The model dynamically simulates mud-filtrate invasion processes including capillary pressure effects and relative permeability, allowing accurate representation of invasion profiles in horizontal and deviated wells without requiring overly complex empirical parameters.
Solution Approach 2:
The patent introduces a physics-based fluid flow simulator as an intermediary between the induction logging measurements and the inversion process. This simulator acts as a mediator that translates petrophysical parameters (permeability, porosity, capillary pressure, relative permeability) into predicted invasion profiles, which then constrain the inversion of electromagnetic data to produce accurate formation resistivity and saturation distributions.
2Adaptability or versatility
If pixel-based inversion method is used to handle complex reservoir configurations, then the inversion can accommodate complex geometries, but the number of unknowns increases significantly requiring inversion of a large number of model parameters
Solution Approach 1:
The patent applies segmentation by dividing the formation into discrete depth intervals or zones, with each zone characterized by a small set of petrophysical parameters (permeability, porosity, capillary pressure, relative permeability) rather than inverting for resistivity at every pixel location. This segmentation reduces the number of unknowns while maintaining the ability to handle complex geometries through the physics-based fluid flow simulator that operates on these segmented zones.
3Device complexity
If conventional single-phase fluid flow model is used for formation test interpretation, then the interpretation process is simpler, but the accuracy deteriorates when mud-filtrate invasion is present
Solution Approach 1:
The patent applies parameter changes by transitioning from a single-phase fluid flow model to a multi-phase model that incorporates additional critical parameters: capillary pressure and relative permeability. These parameter changes enable the model to accurately represent mud-filtrate invasion processes, where multiple fluid phases (mud-filtrate, formation water, hydrocarbons) coexist and interact, thereby improving formation test interpretation accuracy in invaded zones.
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 enables accurate estimation of fluid invasion rates and porosity with improved reliability and efficiency, suitable for complex well configurations, and reduces the need for time-consuming mud-cake simulation, enhancing the accuracy of reservoir characterization.
Implementation Method 1
Induction logging measurements are sensitive to water saturation and brine concentration in the rock pores
Implementation Method 2
the temporal and spatial distribution of water saturation and salt concentration, which in turn can be transformed into the distribution of formation conductivity
Data Source
AI summary
Methods and related systems are described relating to an inversion approach for interpreting the geophysical electromagnetic data. The inversion can be constrained by using a multiphase fluid flow simulator (incorporating pressure data if available) which simulates the fluid flow process and calculates the spatial distribution of the water saturation and the salt concentration, which are in turn transformed into the formation conductivity using a resistivity-saturation formula. In this way, the inverted invasion profile is consistent with the fluid flow physics and moreover accounts for gravity segregation effects. Jointly with the pressure data, the inversion estimates a parametric one-dimensional distribution of permeability and porosity. The fluid flow volume is directly inverted from the fluid-flow-constrained inversion of the electromagnetic data.