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Technical implications of neglecting compositional grading effects in petroleum reservoir simulation models

Technical implications of neglecting compositional grading effects in petroleum reservoir simulation models
Technical implications of neglecting compositional grading effects in petroleum reservoir simulation models
Most compositional reservoir simulation practices assume that the compositions of various fluid components are the same at all locations within the reservoir system. This constant composition assumption is incorrect and unrealistic as it grossly ignores the occurrences of some less obvious physical processes in the reservoir. Gravitational force, temperature gradient, and thermal diffusion, among other factors, contribute to distribution and gradation of hydrocarbon fluid compositions in the reservoir. Therefore, incorporating compositional grading models that adequately account for the individual and combined effects of gravity force, temperature gradient, and thermal diffusion is crucial when initializing reservoir simulation models. This research seeks to elucidate the technical implications of compositional grading on improved reserve estimation and reservoir performance prediction. The mathematical framework for the compositional grading modeling is based on one-dimensional zero-mass-flow stationary state assumption. The Computer Modeling Group’s equation of state multiphase equilibrium property simulator, WinProp, was used for the fluid modeling, while the Computer Modeling Group’s compositional reservoir simulator, GEM, was used for the reservoir modeling and simulation. In the absence of historical production data, Computer Modeling Group’s CMOST was used to perform uncertainty assessment for the validation of the initialized reservoir models. The research results show that initialized reservoir models that neglected or inadequately accounted for compositional grading effects overestimated oil in-place and underestimated gas in-place. The constant composition (without compositional grading) initialized reservoir model overestimates ultimate cumulative oil production by 14.271 MMbbl more than the isothermal compositional grading model and 24.088 MMbbl more than Kempers’ thermal diffusion compositional grading initialized reservoir model. It underestimated ultimate cumulative gas production by 30.133 Bft3 less than the isothermal compositional grading and 50.408 Bft3 less than Kempers’ thermal diffusion compositional grading initialized reservoir model. These figures suggest that neglecting compositional grading or an inadequate account of compositional grading effects in reservoir simulation initialization has detrimental technical consequences.
0887-0624
1467-1481
Igwe, Ikechi
be9f2d4a-c741-4aa0-96e3-d653bb2fbd25
Gholinezhad, Jebraeel
79d96efe-2057-4b95-8be1-4d83162c937a
Hassan Sayed, Mohamed Galal
ce323212-f178-4d72-85cf-23cd30605cd8
Ogbuagu, Frank
59fbe6c7-08be-4f3e-bd1c-1b54e9fca7aa
Igwe, Ikechi
be9f2d4a-c741-4aa0-96e3-d653bb2fbd25
Gholinezhad, Jebraeel
79d96efe-2057-4b95-8be1-4d83162c937a
Hassan Sayed, Mohamed Galal
ce323212-f178-4d72-85cf-23cd30605cd8
Ogbuagu, Frank
59fbe6c7-08be-4f3e-bd1c-1b54e9fca7aa

Igwe, Ikechi, Gholinezhad, Jebraeel, Hassan Sayed, Mohamed Galal and Ogbuagu, Frank (2020) Technical implications of neglecting compositional grading effects in petroleum reservoir simulation models. Energy & Fuels, 34 (2), 1467-1481. (doi:10.1021/acs.energyfuels.9b03528).

Record type: Article

Abstract

Most compositional reservoir simulation practices assume that the compositions of various fluid components are the same at all locations within the reservoir system. This constant composition assumption is incorrect and unrealistic as it grossly ignores the occurrences of some less obvious physical processes in the reservoir. Gravitational force, temperature gradient, and thermal diffusion, among other factors, contribute to distribution and gradation of hydrocarbon fluid compositions in the reservoir. Therefore, incorporating compositional grading models that adequately account for the individual and combined effects of gravity force, temperature gradient, and thermal diffusion is crucial when initializing reservoir simulation models. This research seeks to elucidate the technical implications of compositional grading on improved reserve estimation and reservoir performance prediction. The mathematical framework for the compositional grading modeling is based on one-dimensional zero-mass-flow stationary state assumption. The Computer Modeling Group’s equation of state multiphase equilibrium property simulator, WinProp, was used for the fluid modeling, while the Computer Modeling Group’s compositional reservoir simulator, GEM, was used for the reservoir modeling and simulation. In the absence of historical production data, Computer Modeling Group’s CMOST was used to perform uncertainty assessment for the validation of the initialized reservoir models. The research results show that initialized reservoir models that neglected or inadequately accounted for compositional grading effects overestimated oil in-place and underestimated gas in-place. The constant composition (without compositional grading) initialized reservoir model overestimates ultimate cumulative oil production by 14.271 MMbbl more than the isothermal compositional grading model and 24.088 MMbbl more than Kempers’ thermal diffusion compositional grading initialized reservoir model. It underestimated ultimate cumulative gas production by 30.133 Bft3 less than the isothermal compositional grading and 50.408 Bft3 less than Kempers’ thermal diffusion compositional grading initialized reservoir model. These figures suggest that neglecting compositional grading or an inadequate account of compositional grading effects in reservoir simulation initialization has detrimental technical consequences.

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More information

e-pub ahead of print date: 21 January 2020
Published date: 20 February 2020
Additional Information: doi: 10.1021/acs.energyfuels.9b03528

Identifiers

Local EPrints ID: 438290
URI: http://eprints.soton.ac.uk/id/eprint/438290
ISSN: 0887-0624
PURE UUID: d45229e6-cff3-4c8e-ba99-589acfa75604
ORCID for Mohamed Galal Hassan Sayed: ORCID iD orcid.org/0000-0003-3729-4543

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Date deposited: 04 Mar 2020 17:33
Last modified: 18 Feb 2021 17:41

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Contributors

Author: Ikechi Igwe
Author: Jebraeel Gholinezhad
Author: Mohamed Galal Hassan Sayed ORCID iD
Author: Frank Ogbuagu

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