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arxiv: 2604.20731 · v1 · submitted 2026-04-22 · 🧮 math.NA · cs.NA· cs.NE

CO₂ sequestration hybrid solver using isogeometric alternating-directions and collocation-based robust variational physics informed neural networks (IGA-ADS-CRVPINN)

Pith reviewed 2026-05-09 23:31 UTC · model grok-4.3

classification 🧮 math.NA cs.NAcs.NE
keywords CO2 sequestrationhybrid solverisogeometric analysisphysics-informed neural networksDarcy's lawporous media flowalternating directionsvariational methods
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The pith

A hybrid solver pairs an isogeometric alternating-directions method for saturation with a pretrained neural network for pressure to simulate CO2 flow more than three times faster than a direct solver baseline.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper establishes a hybrid numerical approach for tracking the physical movement of CO2 through porous rock structures using only Darcy's law and no chemical reactions. An explicit isogeometric alternating-directions solver advances the saturation field at each time step while a collocation-based robust variational physics-informed neural network, pretrained once on the starting pressure, computes each new pressure field in just 100 Adam iterations. On a single compute node this combination finishes the full run in less than one-third the time required by the same geometric solver paired with a standard direct linear solver. Readers would care because the speed gain makes repeated, longer, or larger-scale forecasts of underground carbon storage practical on modest hardware.

Core claim

The central claim is that the IGA-ADS-CRVPINN hybrid solver produces accurate time-dependent saturation and pressure fields for the two-phase Darcy flow problem while delivering more than a threefold reduction in wall-clock time relative to the IGA-ADS-MUMPS baseline; the reduction is obtained by performing a single pretraining of the neural network on the initial pressure configuration and then limiting each subsequent pressure update to 100 Adam steps.

What carries the argument

The CRVPINN component, a collocation-based robust variational physics-informed neural network that approximates the pressure scalar field after one-time pretraining and requires only a fixed small number of optimization steps at every new time level.

If this is right

  • The complete simulation finishes in less than one-third the wall-clock time of the baseline direct-solver run on identical hardware.
  • Saturation is advanced explicitly by the alternating-directions isogeometric method without reported stability loss in the presented cases.
  • Pressure accuracy is preserved across many time steps by the lightweight neural updates rather than full retraining or direct solves.
  • The formulation deliberately excludes chemical reactions so that the same splitting can be reused for related storage problems such as hydrogen.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the fixed-iteration neural updates prove stable, the method could support ensembles of simulations over varied porous geometries to quantify storage reliability.
  • The same explicit-plus-neural split could accelerate other multiphase porous-media models in which pressure solves dominate runtime.
  • Faster forward runs would make repeated solution of inverse problems, such as inferring rock properties from observed CO2 plumes, computationally affordable.

Load-bearing premise

The neural-network pressure updates remain accurate and do not accumulate unacceptable error over the full duration of the simulation when limited to 100 Adam iterations after the initial pretraining.

What would settle it

A side-by-side run in which the hybrid solver's pressure and saturation fields after several hundred time steps are compared against a reference solution from the direct solver, checking whether mass-conservation error or plume-front location begins to diverge beyond a chosen tolerance.

Figures

Figures reproduced from arXiv: 2604.20731 by Askold Vilkha, Maciej Paszy\'nski, Marcin {\L}o\'s, Tomasz S{\l}u\.zalec.

Figure 1
Figure 1. Figure 1: Porosity distributions for three different reservoir configurations. The values range from 0 [PITH_FULL_IMAGE:figures/full_fig_p012_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Permeability distributions for three different reservoir configurations. The units are in [PITH_FULL_IMAGE:figures/full_fig_p012_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: CO2 saturation evolution for configuration K1 with uniform permeability at different time [PITH_FULL_IMAGE:figures/full_fig_p014_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: CO2 saturation evolution for configuration K2 with uniform permeability at different time [PITH_FULL_IMAGE:figures/full_fig_p015_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: CO2 saturation evolution for configuration K3 with uniform permeability at different time [PITH_FULL_IMAGE:figures/full_fig_p016_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: CO2 saturation evolution for configuration K1 with non-uniform permeability at different [PITH_FULL_IMAGE:figures/full_fig_p017_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: CO2 saturation evolution for configuration K2 with non-uniform permeability at different [PITH_FULL_IMAGE:figures/full_fig_p018_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: CO2 saturation evolution for configuration K3 with non-uniform permeability at different [PITH_FULL_IMAGE:figures/full_fig_p019_8.png] view at source ↗
Figure 9
Figure 9. Figure 9: CRVPINN pressure solution comparison with IGA-ADS solver for configuration K1 with [PITH_FULL_IMAGE:figures/full_fig_p020_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: CRVPINN pressure solution comparison with IGA-ADS solver for configuration K2 with [PITH_FULL_IMAGE:figures/full_fig_p021_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: CRVPINN pressure solution comparison with IGA-ADS solver for configuration K3 with [PITH_FULL_IMAGE:figures/full_fig_p022_11.png] view at source ↗
Figure 12
Figure 12. Figure 12: CRVPINN pressure solution comparison with IGA-ADS solver for configuration K1 with [PITH_FULL_IMAGE:figures/full_fig_p023_12.png] view at source ↗
Figure 13
Figure 13. Figure 13: CRVPINN pressure solution comparison with IGA-ADS solver for configuration K2 with [PITH_FULL_IMAGE:figures/full_fig_p024_13.png] view at source ↗
Figure 14
Figure 14. Figure 14: CRVPINN pressure solution comparison with IGA-ADS solver for configuration K3 with [PITH_FULL_IMAGE:figures/full_fig_p025_14.png] view at source ↗
Figure 16
Figure 16. Figure 16: CRVPINN loss for uniform permeabil￾ity field (a) Configuration K1 (b) Configuration K2 (c) Configuration K3 [PITH_FULL_IMAGE:figures/full_fig_p031_16.png] view at source ↗
Figure 18
Figure 18. Figure 18: Execution times for IGA-ADS solver for saturation coupled with MUMPS solver executed [PITH_FULL_IMAGE:figures/full_fig_p032_18.png] view at source ↗
Figure 19
Figure 19. Figure 19: Execution times for IGA-ADS solver for saturation coupled with CVPINN solver executed [PITH_FULL_IMAGE:figures/full_fig_p033_19.png] view at source ↗
read the original abstract

This paper presents the hybrid solver for a $CO_2$ sequestration problem. The solver uses the IGA-ADS (IsoGeometric Analysis Alternating Directions solver) to compute the saturation scalar field update using the explicit method, and CRVPINN (Collocation-based Robust Variational Physics Informed Neural Networks solver) to compute the pressure scalar field. The study focuses on simulating the physical behavior of $CO_2$ in porous structures, excluding chemical reactions. The mathematical model is based on Darcy's Law. The CRVPINN is pretrained on the initial pressure configuration, and the time step pressure updates require only 100 iterations of the Adam method per time step. We compare our hybrid IGA-ADS solver, coupled with the CRVPINN method, with a baseline of the IGA-ADS solver coupled with the MUMPS direct solver. Our hybrid solver is over 3 times faster on a single computational node from the ARES cluster of ACK CYFRONET. Future work includes extensive testing, inverse problem solving, and potential application to $H_2$ storage problems.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript presents a hybrid solver for CO2 sequestration in porous media using Darcy's law, where IGA-ADS handles explicit saturation updates and CRVPINN computes the pressure field after initial pretraining with only 100 Adam iterations per time step. The central claim is that this IGA-ADS-CRVPINN hybrid is over 3 times faster than the baseline IGA-ADS coupled with the MUMPS direct solver on a single node of the ARES cluster.

Significance. If the CRVPINN pressure solutions remain accurate and stable under the limited per-step optimization budget, the hybrid approach could offer meaningful efficiency gains for time-dependent porous media simulations, enabling larger-scale or parametric studies in geoscience applications. The combination of isogeometric alternating-directions methods with collocation-based variational PINNs is a novel hybrid strategy that merits further exploration if properly validated.

major comments (2)
  1. [Abstract] Abstract: The claim that the hybrid solver 'is over 3 times faster' is presented without any error metrics, L2 norms, pointwise field comparisons, or convergence histories between the CRVPINN pressure and the MUMPS reference solution. This omission makes it impossible to verify that the speedup preserves numerical accuracy over the simulation horizon.
  2. [Numerical results] Numerical results: No quantitative evidence (e.g., error histories, conservation checks, or final-time field comparisons) is supplied to show that the pressure field produced by CRVPINN after pretraining plus 100 Adam iterations per step remains sufficiently close to the direct solver solution, preventing error accumulation that would invalidate the saturation updates.
minor comments (1)
  1. [Abstract] Abstract: Adding a brief statement of the total simulation duration or number of time steps would help readers assess the practical significance of the reported wall-clock improvement.

Simulated Author's Rebuttal

2 responses · 0 unresolved

Thank you for the opportunity to respond to the referee's report. We value the feedback and will revise the manuscript to address the concerns regarding the presentation of accuracy metrics alongside the performance claims.

read point-by-point responses
  1. Referee: [Abstract] Abstract: The claim that the hybrid solver 'is over 3 times faster' is presented without any error metrics, L2 norms, pointwise field comparisons, or convergence histories between the CRVPINN pressure and the MUMPS reference solution. This omission makes it impossible to verify that the speedup preserves numerical accuracy over the simulation horizon.

    Authors: We agree that the abstract should be supported by evidence of maintained accuracy. In the revised version, we will augment the abstract and the results section with L2 error norms, pointwise comparisons, and convergence histories demonstrating that the CRVPINN pressure solutions, after pretraining and 100 Adam iterations, closely match the MUMPS solutions throughout the time steps. This will substantiate that the reported speedup preserves the required numerical fidelity. revision: yes

  2. Referee: [Numerical results] Numerical results: No quantitative evidence (e.g., error histories, conservation checks, or final-time field comparisons) is supplied to show that the pressure field produced by CRVPINN after pretraining plus 100 Adam iterations per step remains sufficiently close to the direct solver solution, preventing error accumulation that would invalidate the saturation updates.

    Authors: The referee correctly identifies a gap in the current manuscript. We will include in the numerical results section detailed error histories (L2 and pointwise), checks for conservation properties where applicable, and comparisons at final time to confirm that the pressure fields from CRVPINN do not deviate significantly from the reference, ensuring no invalidating error accumulation in the coupled saturation updates. These additions will be based on the simulations already performed. revision: yes

Circularity Check

0 steps flagged

No circularity: empirical timing comparison of hybrid solver

full rationale

The manuscript presents an engineering implementation of a hybrid solver (IGA-ADS explicit saturation updates + CRVPINN pressure solves with pretraining plus 100 Adam steps per timestep) and reports wall-clock speedup versus IGA-ADS+MUMPS on a single node. No derivation chain exists; the 3x speedup is stated as a measured outcome of the implementation, not a mathematical prediction or first-principles result. No equation reduces to its own inputs by construction, no fitted parameter is relabeled as a prediction, and no self-citation supplies a uniqueness theorem or ansatz that the central claim depends upon. The CRVPINN iteration budget is an empirical design choice whose long-term accuracy is an assumption (as noted by the skeptic), but that assumption is not smuggled in via circular definition or self-referential citation. The paper is therefore self-contained against external benchmarks and receives the default non-circularity finding.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Insufficient information in the abstract to enumerate free parameters, axioms, or invented entities; the method relies on standard Darcy-law assumptions and neural-network training but no explicit list is supplied.

pith-pipeline@v0.9.0 · 5533 in / 1053 out tokens · 15311 ms · 2026-05-09T23:31:01.824817+00:00 · methodology

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Reference graph

Works this paper leans on

25 extracted references · 25 canonical work pages

  1. [1]

    Klaus S. Lackner. A Guide to CO2 Sequestration.Science, 300(5626):1677–1678, June 2003. Publisher: American Association for the Advancement of Science

  2. [2]

    Storage of fossil fuel-derived carbon dioxide beneath the surface of the Earth.Annual Review of Environment and Resources, 26(Volume 26, 2001):145–166, November 2001

    Sam Holloway. Storage of fossil fuel-derived carbon dioxide beneath the surface of the Earth.Annual Review of Environment and Resources, 26(Volume 26, 2001):145–166, November 2001. Publisher: Annual Reviews

  3. [3]

    Multiphase flow dynamics during CO2 disposal into saline aquifers.Environmental Geology, 42(2):282–295, June 2002

    Karsten Pruess and Julio García. Multiphase flow dynamics during CO2 disposal into saline aquifers.Environmental Geology, 42(2):282–295, June 2002

  4. [4]

    Abushaikha

    Osama Massarweh and Ahmad S. Abushaikha. CO2 sequestration in subsur- face geological formations: A review of trapping mechanisms and monitoring techniques.Earth-Science Reviews, 253:104793, June 2024

  5. [5]

    Number 155 in Mitteilungen / Institut für Wasserbau, Universität Stuttgart

    Andreas Bielinski.Numerical simulation of CO 2 sequestration in geological formations. Number 155 in Mitteilungen / Institut für Wasserbau, Universität Stuttgart. Inst. f. Wasserbau, Stuttgart, 2007. 28

  6. [6]

    Łoś, Maciej Woźniak, Maciej Paszyński, Andrew Lenharth, Muhamm Amber Hassaan, and Keshav Pingali

    Marcin M. Łoś, Maciej Woźniak, Maciej Paszyński, Andrew Lenharth, Muhamm Amber Hassaan, and Keshav Pingali. IGA-ADS: Isogeometric analysis FEM using ADS solver.Computer Physics Communications, 217:99–116, August 2017

  7. [7]

    Fast parallel IGA-ADS solver for time-dependent Maxwell’s equations.Computers & Mathematics with Applications, 151:36–49, December 2023

    Marcin Łoś, Maciej Woźniak, Keshav Pingali, Luis Emilio Garcia Castillo, Julen Alvarez-Aramberri, David Pardo, and Maciej Paszyński. Fast parallel IGA-ADS solver for time-dependent Maxwell’s equations.Computers & Mathematics with Applications, 151:36–49, December 2023

  8. [8]

    Tuning Two-Dimensional Tumor Growth Simulations

    Leszek Siwik, Marcin Łoś, Adrian Kłusek, Witold Dzwinel, and Maciej Paszyński. Tuning Two-Dimensional Tumor Growth Simulations. InProceedings of the 50th Computer Simulation Conference, University of Bordeaux, Bordeaux, France,

  9. [9]

    Society for Modeling and Simulation International (SCS)

  10. [10]

    Collocation-based robust variational physics-informed neural networks (CRVPINNs).Computers & Structures, 316:107839, September 2025

    Marcin Łoś, Tomasz Służalec, Paweł Maczuga, Askold Vilkha, Carlos Uriarte, and Maciej Paszyński. Collocation-based robust variational physics-informed neural networks (CRVPINNs).Computers & Structures, 316:107839, September 2025

  11. [11]

    Robust variational physics-informed neural networks.Computer Methods in Applied Mechanics and Engineering, 425:116904, 2024

    Sergio Rojas, Paweł Maczuga, Judit Muñoz-Matute, David Pardo, and Maciej Paszyński. Robust variational physics-informed neural networks.Computer Methods in Applied Mechanics and Engineering, 425:116904, 2024

  12. [12]

    Karniadakis

    Ehsan Kharazmi, Zhongqiang Zhang, and George E.M. Karniadakis. hp-vpinns: Variational physics-informed neural networks with domain decomposition.Com- puter Methods in Applied Mechanics and Engineering, 374:113547, 2021

  13. [13]

    Kevrekidis, Lu Lu, Paris Perdikaris, Sifan Wang, and Liu Yang

    George Em Karniadakis, Ioannis G. Kevrekidis, Lu Lu, Paris Perdikaris, Sifan Wang, and Liu Yang. Physics-informed machine learning.Nature Reviews Physics, 3(6):422–440, June 2021. Publisher: Nature Publishing Group

  14. [14]

    Amestoy, I

    P.R. Amestoy, I. S. Duff, J. Koster, and J.-Y. L’Excellent. A fully asynchronous multifrontal solver using distributed dynamic scheduling.SIAM Journal on Matrix Analysis and Applications, 23(1):15–41, 2001

  15. [15]

    Amestoy, A

    P.R. Amestoy, A. Buttari, J.-Y. L’Excellent, and T. Mary. Performance and Scalability of the Block Low-Rank Multifrontal Factorization on Multicore Architectures.ACM Transactions on Mathematical Software, 45:2:1–2:26, 2019. 29

  16. [16]

    CO2 leakage through an abandoned well: problem-oriented benchmarks.Computational Geosciences, 11(2):103–115, June 2007

    Anozie Ebigbo, Holger Class, and Rainer Helmig. CO2 leakage through an abandoned well: problem-oriented benchmarks.Computational Geosciences, 11(2):103–115, June 2007

  17. [17]

    Hosseini, Clyde Lee Giles, and Daniel Kifer

    Parisa Shokouhi, Vikas Kumar, Sumedha Prathipati, Seyyed A. Hosseini, Clyde Lee Giles, and Daniel Kifer. Physics-informed deep learning for prediction ofCO2 storage site response.Journal of Contaminant Hydrology, 241:103835, August 2021

  18. [18]

    Nathan Collier, David Pardo, Lisandro Dalcin, Maciej Paszynski, and V.M. Calo. The cost of continuity: A study of the performance of isogeometric finite elements using direct solvers.Computer Methods in Applied Mechanics and Engineering, 213-216:353–361, 2012

  19. [19]

    Kingma and Jimmy Ba

    Diederik P. Kingma and Jimmy Ba. Adam: A method for stochastic optimization. In Yoshua Bengio and Yann LeCun, editors,ICLR (Poster), 2015

  20. [20]

    Ares cluster, https://docs.cyfronet.pl/spaces/˜plgpawlik/pages/110728307/ares

  21. [21]

    e-Science on distributed computing infrastructure

    Kazimierz Wiatr Marian Bubak, Jacek Kitowski. e-Science on distributed computing infrastructure. Achievements of plgrid plus domain-specific services and tools.Lecture Notes in Computer Science, (8500), 2014

  22. [22]

    On the parallelization of self-adaptive hp-finite element methods part i

    Maciej Paszyński. On the parallelization of self-adaptive hp-finite element methods part i. composite programmable graph grammar model.Fundamenta Informaticae, 93(4):411–434, 2009

  23. [23]

    On the parallelization of self-adaptive hp-finite element methods part ii

    Maciej Paszyński. On the parallelization of self-adaptive hp-finite element methods part ii. partitioning communication agglomeration mapping (pcam) analysis.Fundamenta Informaticae, 93(4):435–457, 2009

  24. [24]

    Multi-deme, twin adaptive strategy hp-hgs.Inverse Problems in Science and Engineering, 19(1):3–16, 2011

    Barbara Barabasz, Stanisław Migórski, Robert Schaefer, and Maciej Paszyński. Multi-deme, twin adaptive strategy hp-hgs.Inverse Problems in Science and Engineering, 19(1):3–16, 2011

  25. [25]

    A hybrid method for inversion of 3d dc resistivity logging mea- surements.Natural computing, 14(3):355–374

    Ewa Gajda-Zagórska, Robert Schaefer, Maciej Smołka, Maciej Paszyński, and David Pardo. A hybrid method for inversion of 3d dc resistivity logging mea- surements.Natural computing, 14(3):355–374. 30 (a) Configuration K1 (b) Configuration K2 (c) Configuration K3 Figure 16: CRVPINN loss for uniform permeabil- ity field (a) Configuration K1 (b) Configuration ...