Release updates
As part of our ongoing commitment to excellence, we continuously innovate to enhance our product. This latest version brings multiple improvements, updates, and bug-fixes to benefit our users. The most important improvements are mentioned in this document below. Please read the release notes for the full overview.
Update of Symmetry Library
The latest Symmetry™ fluid engine release brings major stability and accuracy improvements for Olga compositional tracking and Symmetry flashes. Key highlights include:
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Masked floating-point exceptions and corrected phase identification for gas–aqueous systems.
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Enhanced pressure-enthalpy (P-H)-flash handling with consistent schemes for pressure-temperature (P–T) and PH flashes, ensuring stable density derivatives.
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Fixes for internal flashes in inert and simplified three-phase cases when fluids are pure water or aqueous compounds.
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Improved vapor-liquid equilibrium (VLE) predictions for CO₂–natural gas mixtures and better P-H-flash solutions for low-boiling-point fluids.
Update of Multiflash Library
The KBC Multiflash library has been upgraded from 7.5 to 7.6, delivering improved accuracy and robustness for compositional tracking simulations. Highlights include:
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Enhanced advanced cubic EOS model with updated binary interaction parameters (BIPs) and component properties for better accuracy.
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More robust extrapolation near the critical point for continuous property predictions (notably heat capacity and enthalpy).
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Faster model initialization and updated EOS-CG (Combustion Gas) to the latest 2021 publication.
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Improved handling outside validity ranges with a fallback cubic EOS method, while high-accuracy aqueous EOS remains active for tracking.
Additional improvements:
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Better viscosity tuning with Pedersen and LBC models.
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Updated mercury model. Licenses will be available through SLB.
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Added THF and carbon monoxide as hydrate formers.
Update of PVTSim Library
The latest PVTSim Nova 7.2 release introduces key enhancements for Olga simulator integration:
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Compositional tracking with PH Flash is now supported.
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New option in the Olga tab file interface lets users control liquid–liquid splits. When two non-aqueous liquid phases occur (e.g. two hydrocarbons or a hydrocarbon and CO₂-rich phase), you can choose to merge them into one liquid or treat the lighter phase as gas in the tab file.
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Ability to generate Olga PH tab files in both PVTSim Nova and PVTSim Nova CCS.
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Directional leak functionality
The new directional leak feature improves depressurization simulations for stratified flow regimes, where gas sits above liquid in the pipeline. Unlike the default model (which assumes a well-mixed fluid), this functionality calculates leaked gas and liquid fractions based on:
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Leak angle (position around the pipe circumference)
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Leak diameter
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Liquid level
This allows more realistic modeling of leaks dominated by either gas or liquid, depending on their position. Directional leak is only compatible with Olga new solver (CCS) in Olga 2026.1.
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Equilibrium fluid model for pumps and compressors
Olga simulator now supports a new FLUIDMODEL key for centrifugal pumps and compressors, with two options:
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IDEAL (default in Olga 2025.2 and earlier): assumes ideal gas and incompressible liquid.
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• EQUILIBRIUM: uses the specified equation of state for more accurate calculations of pump head/torque and compressor compression ratio, without idealized assumptions.
CO₂ flow model
A dedicated CO₂ flow model is now available when the solver option is set to Olga new solver (CCS) and the flow model is set to Olga. It is designed for CO₂-dominated gas–liquid two-phase flow and ensures accurate simulation for these conditions. Compared to the Olga friction factor model, the pressure drop error is reduced by 51%, the hold-up error is decreased by approximately 31%, and the accuracy of flow regime prediction is increased by 34%.
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Error on the pressure drop
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Error on the hold up
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Flow regime prediction accuracy
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CO2 model improvement
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Reduced by 51%
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Reduced by 31%
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Increased by 34%
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Table 1 - Improvements for the CO2 model compared to the Olga friction factor flow model
Security enhancements
As part of SLB’s Software Lifecycle Management process, SLB will conduct tests to ensure that the software is free from security vulnerabilities and malicious codes, including viruses, trapdoors, trojan horses, or ransomware that could render the software inoperable or prevent its use as documented. If SLB becomes aware of such a threat, it will use commercially reasonable efforts to provide a patch or updated version of the software to eliminate or mitigate the issue, making it available for download or installation by the customer. SLB is not responsible for viruses introduced at the customer’s site or those that did not originate from the software.
With increased focus on security from both customers and internal initiatives, three scanning tools have been introduced for Olga simulator: Mend, Spectra Assure and FlexNet from Flexera. These tools scan for vulnerabilities and enable updates or replacement of outdated libraries.
Additionally, a penetration test was conducted on Olga simulator by a third-party company, which was successfully completed from the project’s perspective.
New output variables
Two new reservoir output variables have been added:
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DPRES – Draw-down pressure
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TMRES – Reservoir temperature
These variables provide enhanced monitoring and analysis capabilities for reservoir performance.
Additional variables have been added to capture and locate the minimum and maximum inner wall surface temperature (TWS) in branches.
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MAXTWSBR – Maximum inner wall surface temperature in branch since start
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MAXTWSPOS – Distance from branch inlet where maximum inner wall surface temperature since start occurs
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MAXTWSBRCT – Maximum inner wall surface temperature in branch at current time
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MINTWSBR – Minimum inner wall surface temperature in branch since start
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MINTWSPOS – Distance from branch inlet where minimum inner wall surface temperature since start occurs
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MINTWSBRCT – Minimum inner wall surface temperature in branch at current time
Node function improvements
Several updates have been made to node functionality:
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INTERNAL node type renamed to MANIFOLD for clearer terminology.
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Sources (mass flow, pressure-driven, or tracer) can now be added to manifold, separator, and phase split nodes, with the same capabilities as sources in flowpaths.
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MASSFLOW node is obsolete and replaced by the manifold node.
Olga simulator cases created in version 2025.2 or earlier that include mass or internal nodes are automatically converted to manifold nodes when opened in the current Olga UI. Cases using manifold nodes are not backward compatible with older versions.
Steady-state preprocessor enhancements
The steady-state preprocessor (SSPP) now includes support for injection wells and negative pressure-driven sources, enabling more accurate modeling of CCS injection and drilling scenarios.
New options have been added to the steady-state preprocessor for RESREVOIRCONTACT through a new key INIWELLFLOW under BRANCH keyword. The following options are available:
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Limit the solution to production only (PRODUCTION).
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Limit the solution to injection only (INJECTION).
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No limit on the solution. The steady-state preprocessor starts with a guessed production rate (INITPRODUCTION).
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No limit on the solution. The steady-state preprocessor starts with a guessed injection rate (INITINJECTION).
Performance improvements
Computational speed in the Olga simulator has been significantly increased through enhanced parallel processing.
Parallel processing has been optimized, providing additional benefits for running parallel simulations across most computer architectures. This improvement typically reduces simulation time by a factor of two to three (case-dependent) compared to Olga 2025.2. running simulations on four threads.
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