Research Article | | Peer-Reviewed

Simplified Neural Network-Based Models for Oil Flow Rate Prediction

Received: 2 August 2024     Accepted: 9 September 2024     Published: 23 September 2024
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Abstract

Available neural network-based models for predicting the oil flow rate (qo) in the Niger Delta are not simplified and are developed from limited data sources. The reproducibility of these models is not feasible as the models’ details are not published. This study developed simplified and reproducible three, five, and six-input variables neural-based models for estimating qo using 283 datasets from 21 wells across fields in the Niger Delta. The neural-based models were developed using maximum-minimum (max.-min.) normalized and clip-normalized datasets. The performances and the generalizability of the developed models with published datasets were determined using some statistical indices: coefficient of determination (R2), mean square error (MSE), root mean square error (RMSE), average relative error (ARE) and average absolute relative error (AARE). The results indicate that the 3-input-based neural models had overall R2, MSE, and RMSE values of 0.9689, 9.6185x10-4 and 0.0310, respectively, for the max.-min. normalizing method and R2 of 0.9663, MSE of 5.7986x10-3 and RMSE of 0.0762 for the clip scaling approach. The 5-input-based models resulted in R2 of 0.9865, MSE of 5.7790×10-4 and RMSE of 0.0240 for the max.-min. scaling method and R2 of 0.9720, MSE of 3.7243x10-3 and RMSE of 0.0610 for the clip scaling approach. Also, the 6-input-based models had R2 of 0.9809, MSE of 8.7520x10-4 and RMSE of 0.0296 for the max.-min. normalizing approach and R2 of 0.9791, MSE of 3.8859 x 10-3 and RMSE of 0.0623 for the clip scaling method. Furthermore, the generality performance of the simplified neural-based models resulted in R2, RMSE, ARE, and AAPRE of 0.9644, 205.78, 0.0248, and 0.1275, respectively, for the 3-input-based neural model and R2 of 0.9264, RMSE of 2089.93, ARE of 0.1656 and AARE of 0.2267 for the 6-input-based neural model. The neural-based models predicted qo were more comparable to the test datasets than some existing correlations, as the predicted qo result was the lowest error indices. Besides, the overall relative importance of the neural-based models’ input variables on qo prediction is S>GLR>Pwh>T/Tsco>BS&W>γg. The simplified neural-based models performed better than some empirical correlations from the assessment indicators. Therefore, the models should apply as tools for oil flow rate prediction in the Niger Delta fields, as the necessary details to implement the models are made visible.

Published in Petroleum Science and Engineering (Volume 8, Issue 2)
DOI 10.11648/j.pse.20240802.12
Page(s) 70-99
Creative Commons

This is an Open Access article, distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution and reproduction in any medium or format, provided the original work is properly cited.

Copyright

Copyright © The Author(s), 2024. Published by Science Publishing Group

Keywords

Neural Network, Normalization Methods, Simplified Neural-Based Models, Oil Flow Rate, Niger Delta

References
[1] Bikmukhametov T, Jäschke J (2020) First principles and machine learning virtual flow metering: A literature review. J Pet Sci Eng, 184: 106487-106592.
[2] Al-Jawad MS, Ottba DJS (2006) Well performance analysis based on flow calculations and IPR. J Eng, 13(3): 822-841.
[3] Agwu OE, Alkouh A, Alatefi S, Azim RA, Ferhadi R (2024) Utilization of machine learning for the estimation of production rates in wells operated by electrical submersible pumps. J Pet Explor Prod Technol, 14: 1205–1233.
[4] Beiranvand MS, Mohammadmoradi P, Aminshahidy B, Fazelabdolabadi B, Aghahoseini S (2012) New multiphase choke correlations for a high flow rate Iranian Oil Field. J Mech Sci, 3: 43-47.
[5] Okon AN, Appah D (2018) Water coning prediction: An evaluation of horizontal well correlations. Eng and Applied Sci J, 3(1): 21-28.
[6] Ejoh E (2017) How Nigeria ‘lost N2 trillion to poor metering of oil wells’ in two years. Vanguard Online.
[7] Brill JP (2010) Modeling multiphase flow in pipes. Soc Pet Eng.: The Way Ahead, 6(2): 16-17.
[8] Lak A, Azin R, Osfouri S, Fatehi R (2017) Modelling critical flow through choke for a gas-condensate reservoir based on drill stem test data. Iranian J Oil & Gas Sci and Technol, 6(3): 29-40.
[9] Nasriani HR, Kalantariasl A (2011) Two-phase flow choke performance in high-rate gas condensate wells. Paper presented at the Society of Petroleum Engineers Asia Pacific Oil and Gas Conference and Exhibition, Jakarta, Indonesia, 20-22 Sept. 2011.
[10] Hong KC, Griston S (1997) Best practice for the distribution and metering of two-phase steam. Soc Pet Eng. Production Facility, 12(3): 173-80.
[11] Sadatshojaei E, Jamialahmadi M, Esmaeilzadeh F, Ghazanfari MH (2016) Effects of low-salinity water coupled with silica nanoparticles on wettability alteration of dolomite at reservoir temperature. J Pet Sci Technol, 34(15): 1345-1351.
[12] Choubineh A, Ghorbani H, Wood DA, Moosavi SR, Khalafi E, Sadatshojaei E (2017) Improved predictions of wellhead choke liquid critical-flow rates: Modelling based on hybrid neural network training learning-based optimization. Fuel, 207: 547-560.
[13] Al-Attar HH (2009) New correlations for critical and subcritical two-phase flow through surface chokes in high-rate oil wells. Paper presented at the Latin American and Caribbean Petroleum Engineering Conference, Cartagena de Indias, Colombia, 31 May-30 June 2009.
[14] Gilbert WE (1954) Flowing and gas-lift well performance. American Petroleum Institute Drilling & Production Practice, Dallas, Texas, 20: 126-157.
[15] Baxendell PB (1957) Bean Performance-Lake Wells. Shell Internal Report, October 1957.
[16] Ros NCJ (1960) An analysis of critical simultaneous gas/liquid flow through a restriction and its application to flow metering. Applied Sci Res, 9: 374-389.
[17] Achong I (1961) Revised bean performance formula for Lake Maracaibo wells. Shell Internal Report, Oct. 1961.
[18] Omana R, Houssier C, Brown KE, Brill JP, Thompson RE (1968) Multiphase flow through chokes. Paper presented at the Society of Petroleum Engineers Annual Meeting, Denver Colorado, 28 Sept. - 1 Oct. 1968.
[19] Pilehvari AA (1981) Experimental study of critical two-phase flow through wellhead chokes. University of Tulsa Fluid Flow Project Report, Tulsa, USA.
[20] Owolabi OO, Dune KK, Ajienka JA (1991) Producing the multiphase flow performance through wellhead chokes for the Niger Delta oil wells. Paper presented at the International Conference of the Society of Petroleum Engineers Nigeria Section Annual Proceeding, August 1991.
[21] Al-Towailib A, Al-Marhoun MA (1994) A new correlation for two-phase flow through chokes. J Can Pet Technol, 33(5): 40-43.
[22] Khorzoughi MB, Beiranvand M, Rasaei MR (2013) Investigation of a new multiphase flow choke correlation by linear and non-linear optimization methods and Monte Carlo sampling. J Pet Explor Prod Technol, 3: 279-285.
[23] Okon AN, Udoh FD, Appah D (2015) Empirical wellhead pressure production rate correlations for Niger Delta oil wells. Paper presented at the Society of Petroleum Engineers (SPE), Nigeria Council 39th Nigeria Annual International Conference and Exhibition, Eko Hotel and Suite, Lagos, 4-6 Aug. 2015.
[24] Ghorbani H, Wood DA, Choubineh A, Tatar A, Abarghoy PG, Madani M, Mohamadian N (2018) Prediction of oil flow rate through an orifice flow meter: artificial intelligence alternatives compared. Petroleum 6 (4): 404-414.
[25] Alrumah M, Alenezi RA (2019) New universal two-phase choke correlations developed using non-linear multivariable optimization technique. J Eng Res, 7(3): 320-329.
[26] Joshua SK, Oshokosikeshishi LP, Sylvester O (2020) New production rate model of wellhead choke for Niger Delta oil wells. J Pet Sci Tech, 10: 41-49.
[27] Alarifi SA (2022). Workflow to predict wellhead choke performance during multiphase flow using machine learning. J Pet Sci Eng, 214 (2022)110563.
[28] Berneti SM, Shahbazian M (2011) An imperialist competitive algorithm artificial neural network method to predict oil flow rate of the wells. Int. J. Comput. Appl. 26(10): 47-50.
[29] Mirzaei-Paiaman A, Salavati S (2012) The application of artificial neural networks for the prediction of oil production flow rate. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 34(19): 1834-1843.
[30] Al-Khalifa MA, Al-Marhoun MA (2013) Application of neural network for two-phase flow through chokes. Paper presented at the Society of Petroleum Engineers Saudi Arabia section Annual Technical Symposium and Exhibition, Khobar, Saudi Arabia, 19-22 May 2013.
[31] Zangl G, Hermann R, Schweiger C (2014) Comparison of methods for stochastic multiphase flow rate estimation. Paper presented at the Society of Petroleum Engineers Annual Technical Conference and Exhibition, Amsterdam, The Netherlands, 27-29 Oct. 2014.
[32] Al-Ajmi MD, Alarifi SA, Mahsoon AH (2015) Improving multiphase choke performance prediction and well production test validation using artificial intelligence: A new milestone. Paper presented at the Society of Petroleum Engineers Digital Energy Conference and Exhibition, Woodlands, Texas, USA, 3-5 Mar. 2015.
[33] Okon AN, Appah D (2016) Neural network models for predicting wellhead pressure-flow rate relationship for Niger Delta oil wells. J Scientific Res Reports, 12(1): 1-14.
[34] Al-Qutami TA, Ibrahim R, Ismail I, Ishak MA (2018) Virtual multiphase flow metering using diverse neural network ensemble and adaptive simulated annealing. Expert Syst. Appl. 93(1): 72-85.
[35] Al-Kadem M, Al Dabbous M, Al Mashhad A, Al Sadah H (2019) Utilization of artificial neural networking for real-time oil production rate estimation. Paper presented at the Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, UAE, 11-14 Nov. 2019.
[36] Khan MR, Tariq Z, Abdulraheem A (2020) Application of artificial intelligence to estimate oil flow rate in gas-lift wells. Natural Resources Research, 29: 4017-4029.
[37] Ibrahim NM, Alharbi AA, Alzahrani TA, Abdulkarim AM, Alessa IA, Hameed AM, Albabtain AS, Alqahtani DA, Alsawwaf MK, Almuqhim AA (2022) Well performance classification and prediction: deep learning and machine learning long term regression experiments on oil, gas, and water production. Sensors, 22, 5326.
[38] Okorugbo O, Dune KK, Wami EN (2021) Application of neural network-particle swarm modelling for predicting wellhead choke performance in the Niger Delta. Int J Pet Petrochem Eng, 7(1): 21-29.
[39] Park YS, Lek S (2016) Artificial neural networks: multilayer perceptron for ecological modelling. In S. E. Jørgensen (Ed.), Developments in environmental modelling, 28: 123-140). Elsevier.
[40] Behnoud P, Hosseini P (2017) Estimation of lost circulation amount occurs during under balanced drilling using drilling data and neural network. Egyptian J Pet, 26(3): 627-634.
[41] Mekanik F, Imteaz M, Gato-Trinidad S, Elmahdi A (2013) Multiple regression and artificial neural network for long term rainfall forecasting using large scale climate modes. J. Hydrol, 503(2): 11-21.
[42] Demuth, H., Beale, M., Martin, H. (2009). Neural network toolbox users guide. The Mathworks, Inc, p. 906, Version 6.
[43] Haykin S (1999) Neural networks, a comprehensive foundation, Second ed. Prentice Hall Inc., Upper Saddle River.
[44] Aalst WMP, Rubin V, Verbeek HMW, Van Dongen BF, Kindler E, Günther CW (2010) Process mining: a two-step approach to balance between underfitting and overfitting. Software Syst. Model, 9(1): 87-111.
[45] Anifowose F, Ewenla A, Eludiora S (2012) Prediction of oil and gas reservoir properties using support vector machines. Paper presented at the International Petroleum Technical Conference, Bangkok, Thailand, 7-9 Feb. 2012.
[46] Okon AN, Ansa IB (2021) Artificial neural network models for reservoir aquifer dimensionless variables: influx and pressure prediction for water influx calculation. J Pet Explor Prod Technol, 11(4): 1885-1904.
[47] Perkins TK (1993) Critical and subcritical flow of multiphase mixtures through chokes. Society of Petroleum Engineering Drilling and Completion, 8(4): 271-276.
[48] Ibrahim AF, Al-Dhaif R, Elkatatny S, Al Shehri D (2021) Applications of artificial intelligence to predict oil rate for high gas-oil ratio and water-cut wells. ACS Omega, 6: 19484-19493.
[49] Barjouei HS, Ghorbani H, Mohamadian N, Wood DA, Davoodi S, Moghadasi J, Saberi H (2021) Prediction performance advantages of deep machine learning algorithms for two‑phase flow rates through wellhead chokes. J Pet Explor Prod, 11: 1233–1261.
[50] Ahmadi MA, Ebadi M, Shokrollahi A, Majidic SMJ (2013) Evolving artificial neural network and imperialist competitive algorithm for prediction oil flow rate of the reservoir. Appl. Soft Comput. 13 (2), 1085-1098.
[51] Gorjaei RG, Songolzadeh R, Torkaman M, Safari M, Zargar G (2015) A novel PSO-LSSVM model for predicting liquid rate of two-phase flow through wellhead chokes. J Nat Gas Sci Eng, 24: 228-237.
[52] Hasanvand M, Berneti SM (2015) Predicting oil flow rate due to multiphase flow meter by using an artificial neural network. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 37(8): 840-845.
[53] Baghban A, Abbasi P, Rostami P, Bahadori M, Ahmad Z, Kashiwao T, Bahadori A (2016) Estimation of oil and gas properties in petroleum production and processing operations using rigorous model. J Pet Sci Tech, 34(13): 1129-1136.
[54] Buhulaigah A, Al-Mashhad AS, Al-Arifi SA, Al-Kadem MS, Al-Dabbous MS (2017) Multilateral wells evaluation utilizing artificial intelligence. Paper presented at the Society of Petroleum Engineers Middle East Oil & Gas Show and Conference, Manama, Kingdom of Bahrain, 6-9 Mar. 2017.
[55] Khan MR, Alnuaim S, Tari Z, Abdulraheem A (2019) Machine learning application for oil rate prediction in artificial gas lift wells. Paper presented at the Society of Petroleum Engineers Middle East Oil and Gas Show and Conference, Manama, Bahrain, 18-21 Mar. 2019.
[56] Ghorbani H, Wood, DA, Moghadasi J, Choubineh A, Abdizadeh P, Mohamadian, N (2019) Predicting liquid flow-rate performance through wellhead chokes with genetic and solver optimizers: an oil field case study. J Pet Explor Prod Technol, 9: 1355-1373.
[57] Al-Rumah M, Aladwani F, Alatefi S (2020) Toward the development of a universal choke correlation - global optimization and rigorous computational techniques. J Eng Res, 8(3): 240-254.
[58] Marfo SA, Kporxah C (2020) Predicting oil production rate using artificial neural network and decline curve analytical methods. Proceedings of 6th UMaT Biennial International Mining and Mineral Conference, Tarkwa, Ghana, 43-50.
[59] Azim RA (2022) A new correlation for calculating wellhead oil flow rate using artificial neural network. J Artificial Intelligence in Geosciences, 3: 1-7.
[60] Okon AN, Effiong AJ, Daniel DD (2023) Explicit neural network-based models for bubble point pressure and oil formation volume factor prediction. Arabian J Sci Eng, 48: 9221-9257.
[61] Mahmoudi S, Mahmoudi A (2014) Water saturation and porosity prediction using back-propagation artificial neural network (BPANN) from well log data. J Eng & Technol 5(2): 1-8.
[62] Okon AN, Adewole SE, Uguma EM (2020) Artificial neural network model for reservoir petrophysical properties: porosity, permeability and water saturation prediction. J Model Earth Syst and Environ, 7: 2373-2390.
[63] Abuh FA, Akpabio JU, Okon AN (2023) Machine learning-based models for basic sediment & water and sand-cut prediction in matured Niger Delta fields. J Energy Res Reviews 15(2): 70-93.
[64] Al-Bulushi N, King PR, Blunt MJ, Kraaijveld M (2009) Development of artificial neural network models for predicting water saturation and fluid distribution. J Pet Sci Eng 68: 197-208.
[65] Sircar A, Yadav K, Rayavarapu K, Bist N, Oza H (2021) Application of machine learning and artificial intelligence in oil and industry. Pet Res, 6: 379-391.
[66] Effiong AJ, Etim JO, Okon AN (2021) Artificial intelligence model for predicting formation damage in oil and gas wells. Paper presented at the Society of Petroleum Engineers (SPE), Nigeria Council 45th Nigeria Annual International Conference and Exhibition, 2-4 Aug. 2021.
[67] George A (2021) Predicting oil production flow rate using artificial neural networks – the Volve field case. Paper presented at the Nigeria Annual International Conference and Exhibition, Logas, Nigeria, 2-4 August 2021.
[68] Citakoglu H, Coskun O (2022) Comparison of hybrid machine learning methods for the prediction of short-term meteorological droughts of Sakarga Meterological Station in Turkey. Environ Sci Poll Res.
[69] Demir V (2022) Enhancing monthly lake levels forecasting using heuristic regression techniques with periodicity data component: application of Lake Michigan. Theor Appl Climatol 148: 915-929.
[70] Alexander D, Tropsha A, Winkler D (2015) Beware of R2: simple, unambiguous assessment of the prediction accuracy of QSAR and QSPR Models. J Chem Info Model, 55(7): 1316-1322.
Cite This Article
  • APA Style

    Umana, U. K., Okon, A. N., Agwu, O. E. (2024). Simplified Neural Network-Based Models for Oil Flow Rate Prediction. Petroleum Science and Engineering, 8(2), 70-99. https://doi.org/10.11648/j.pse.20240802.12

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    ACS Style

    Umana, U. K.; Okon, A. N.; Agwu, O. E. Simplified Neural Network-Based Models for Oil Flow Rate Prediction. Pet. Sci. Eng. 2024, 8(2), 70-99. doi: 10.11648/j.pse.20240802.12

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    AMA Style

    Umana UK, Okon AN, Agwu OE. Simplified Neural Network-Based Models for Oil Flow Rate Prediction. Pet Sci Eng. 2024;8(2):70-99. doi: 10.11648/j.pse.20240802.12

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  • @article{10.11648/j.pse.20240802.12,
      author = {Uduak Koffi Umana and Anietie Ndarake Okon and Okorie Ekwe Agwu},
      title = {Simplified Neural Network-Based Models for Oil Flow Rate Prediction
    },
      journal = {Petroleum Science and Engineering},
      volume = {8},
      number = {2},
      pages = {70-99},
      doi = {10.11648/j.pse.20240802.12},
      url = {https://doi.org/10.11648/j.pse.20240802.12},
      eprint = {https://article.sciencepublishinggroup.com/pdf/10.11648.j.pse.20240802.12},
      abstract = {Available neural network-based models for predicting the oil flow rate (qo) in the Niger Delta are not simplified and are developed from limited data sources. The reproducibility of these models is not feasible as the models’ details are not published. This study developed simplified and reproducible three, five, and six-input variables neural-based models for estimating qo using 283 datasets from 21 wells across fields in the Niger Delta. The neural-based models were developed using maximum-minimum (max.-min.) normalized and clip-normalized datasets. The performances and the generalizability of the developed models with published datasets were determined using some statistical indices: coefficient of determination (R2), mean square error (MSE), root mean square error (RMSE), average relative error (ARE) and average absolute relative error (AARE). The results indicate that the 3-input-based neural models had overall R2, MSE, and RMSE values of 0.9689, 9.6185x10-4 and 0.0310, respectively, for the max.-min. normalizing method and R2 of 0.9663, MSE of 5.7986x10-3 and RMSE of 0.0762 for the clip scaling approach. The 5-input-based models resulted in R2 of 0.9865, MSE of 5.7790×10-4 and RMSE of 0.0240 for the max.-min. scaling method and R2 of 0.9720, MSE of 3.7243x10-3 and RMSE of 0.0610 for the clip scaling approach. Also, the 6-input-based models had R2 of 0.9809, MSE of 8.7520x10-4 and RMSE of 0.0296 for the max.-min. normalizing approach and R2 of 0.9791, MSE of 3.8859 x 10-3 and RMSE of 0.0623 for the clip scaling method. Furthermore, the generality performance of the simplified neural-based models resulted in R2, RMSE, ARE, and AAPRE of 0.9644, 205.78, 0.0248, and 0.1275, respectively, for the 3-input-based neural model and R2 of 0.9264, RMSE of 2089.93, ARE of 0.1656 and AARE of 0.2267 for the 6-input-based neural model. The neural-based models predicted qo were more comparable to the test datasets than some existing correlations, as the predicted qo result was the lowest error indices. Besides, the overall relative importance of the neural-based models’ input variables on qo prediction is S>GLR>Pwh>T/Tsc>γo>BS&W>γg. The simplified neural-based models performed better than some empirical correlations from the assessment indicators. Therefore, the models should apply as tools for oil flow rate prediction in the Niger Delta fields, as the necessary details to implement the models are made visible.
    },
     year = {2024}
    }
    

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  • TY  - JOUR
    T1  - Simplified Neural Network-Based Models for Oil Flow Rate Prediction
    
    AU  - Uduak Koffi Umana
    AU  - Anietie Ndarake Okon
    AU  - Okorie Ekwe Agwu
    Y1  - 2024/09/23
    PY  - 2024
    N1  - https://doi.org/10.11648/j.pse.20240802.12
    DO  - 10.11648/j.pse.20240802.12
    T2  - Petroleum Science and Engineering
    JF  - Petroleum Science and Engineering
    JO  - Petroleum Science and Engineering
    SP  - 70
    EP  - 99
    PB  - Science Publishing Group
    SN  - 2640-4516
    UR  - https://doi.org/10.11648/j.pse.20240802.12
    AB  - Available neural network-based models for predicting the oil flow rate (qo) in the Niger Delta are not simplified and are developed from limited data sources. The reproducibility of these models is not feasible as the models’ details are not published. This study developed simplified and reproducible three, five, and six-input variables neural-based models for estimating qo using 283 datasets from 21 wells across fields in the Niger Delta. The neural-based models were developed using maximum-minimum (max.-min.) normalized and clip-normalized datasets. The performances and the generalizability of the developed models with published datasets were determined using some statistical indices: coefficient of determination (R2), mean square error (MSE), root mean square error (RMSE), average relative error (ARE) and average absolute relative error (AARE). The results indicate that the 3-input-based neural models had overall R2, MSE, and RMSE values of 0.9689, 9.6185x10-4 and 0.0310, respectively, for the max.-min. normalizing method and R2 of 0.9663, MSE of 5.7986x10-3 and RMSE of 0.0762 for the clip scaling approach. The 5-input-based models resulted in R2 of 0.9865, MSE of 5.7790×10-4 and RMSE of 0.0240 for the max.-min. scaling method and R2 of 0.9720, MSE of 3.7243x10-3 and RMSE of 0.0610 for the clip scaling approach. Also, the 6-input-based models had R2 of 0.9809, MSE of 8.7520x10-4 and RMSE of 0.0296 for the max.-min. normalizing approach and R2 of 0.9791, MSE of 3.8859 x 10-3 and RMSE of 0.0623 for the clip scaling method. Furthermore, the generality performance of the simplified neural-based models resulted in R2, RMSE, ARE, and AAPRE of 0.9644, 205.78, 0.0248, and 0.1275, respectively, for the 3-input-based neural model and R2 of 0.9264, RMSE of 2089.93, ARE of 0.1656 and AARE of 0.2267 for the 6-input-based neural model. The neural-based models predicted qo were more comparable to the test datasets than some existing correlations, as the predicted qo result was the lowest error indices. Besides, the overall relative importance of the neural-based models’ input variables on qo prediction is S>GLR>Pwh>T/Tsc>γo>BS&W>γg. The simplified neural-based models performed better than some empirical correlations from the assessment indicators. Therefore, the models should apply as tools for oil flow rate prediction in the Niger Delta fields, as the necessary details to implement the models are made visible.
    
    VL  - 8
    IS  - 2
    ER  - 

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