Petroleum Fluid Characterization via Exponential Weight Distribution
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Solution Overview
Problem
Current methods for characterizing petroleum fluids, particularly heavier hydrocarbon components, are inadequate for accurate EOS modeling due to limitations in delumping C3-C5 alkane groups and converting weight fractions to mole fractions, leading to inaccurate phase behavior predictions in reservoir simulations.
Innovation Solution
A method and apparatus that utilize a PVT database to derive empirical relations for characterizing alkane components, employing downhole sampling and analysis to estimate properties like weight percentages and molecular weights, which are then used to generate an equation of state model for predicting PVT properties and compositional gradients, including gas hydrate formation, wax precipitation, and asphaltene precipitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional delumping methods are used for C3-C5 alkane groups, then the characterization process is simplified, but the accuracy of EOS modeling deteriorates due to inability to properly convert weight fractions to mole fractions
Solution Approach 1:
The patent transforms the characterization approach by changing from direct delumping of C3-C5 groups to a sequential method: first determining C6+ distribution using exponential functions, then deriving C3-C5 compositions through material balance and equilibrium relationships. This parameter transformation enables accurate conversion between weight and mole fractions while maintaining EOS modeling accuracy.
Solution Approach 2:
The patent segments the hydrocarbon mixture into distinct compositional ranges (C1-C2, C3-C5, C6+) and applies different characterization methods to each segment. The C6+ fraction is characterized using exponential distribution functions, while C3-C5 is determined through equilibrium relationships, allowing each segment to be optimized independently for accurate overall characterization.
2Adaptability or versatility
If exponential distribution is assumed for mole fractions of C7+ components, then the characterization follows conventional approaches, but the accuracy deteriorates due to incorrect assumptions about weight fraction distributions
Solution Approach 1:
The patent inverts the conventional approach by assuming exponential distribution for weight fractions rather than mole fractions. This inversion is based on the observation that weight fraction distributions of heavy hydrocarbons in reservoir fluids follow exponential patterns more consistently than mole fractions, leading to more accurate component concentration predictions when converted to mole fractions for EOS modeling.
3Loss of time
If downhole fluid analysis is performed, then real-time compositional data is obtained, but the complexity of simultaneous phase behavior analysis increases
Solution Approach 1:
The patent performs preliminary characterization of the C6+ fraction using exponential distribution functions before analyzing the complete phase behavior. This preliminary action establishes a reliable foundation for the subsequent determination of C3-C5 compositions through equilibrium relationships, simplifying the overall analysis complexity while maintaining real-time capability.
Solution Approach 2:
The patent uses material balance equations and equilibrium relationships as intermediary tools to connect the measured downhole compositional data with the EOS model requirements. These intermediaries transform the complex simultaneous phase behavior problem into a sequence of manageable calculations, reducing analysis complexity while preserving real-time decision-making capability.
Data Source
AI summary
An improved method and system for characterizing the compositional components of a hydrocarbon reservoir of interest and analyzing fluid properties of the reservoir of interest based upon its compositional components.