Application of Artificial Intelligence to Estimate Oil Flow Rate in Gas-Lift Wells

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Original Paper

Application of Artificial Intelligence to Estimate Oil Flow Rate in Gas-Lift Wells Mohammad Rasheed Khan ,1,3 Zeeshan Tariq ,2 and Abdulazeez Abdulraheem2 Received 1 August 2019; accepted 30 March 2020

Optimization and monitoring schemes for oil well and reservoir system require accurate estimation of production rate. Real-time monitoring is conducted typically using flow transmitters that contain their own inherent uncertainties due to flow of multiple fluids. Because of these limitations, industrial practices involve the usage of wellhead conditions and intermittent well test data to estimate well flow rates through certain established correlations such as GilbertÕs empirical model. These correlations, however, have become ineffective due to inadequate well test data and associated operational and cost-intensive commitments. The main objective of this work was to utilize artificial intelligence (AI) techniques to develop robust correlation to predict oil rates in gas-lift wells. The AI techniques implemented in this study are artificial neural network (ANN), artificial neuro-fuzzy inference systems, support vector machines, and functional networks. In addition, ANN was used to develop physical equation to predict oil flow rate. Separator test dataset from multiple wells of an oil field operating on continuous gas lift was collected. Extensive data analytics were performed before feeding it in the algorithms. The inputs consisted of only the easily available surface parameters. All the developed AI models were compared among themselves as well as with conventionally used empirical models. The comparison was conducted based on average absolute error percentage and coefficient of determination. The newly developed AI model can predict oil rates with accuracy exceeding 98% that is extremely efficient, and examples of such results have not been reported previously. KEY WORDS: Artificial neural network, Artificial intelligence, Machine learning, Petroleum engineering.

INTRODUCTION Multiphase flow occurs in mostly all oil wells at some point in time in the life of a field (Lannom and Hatzignatiou 1994). The main problems associated

1

Software Integrated Solutions, Schlumberger, Islamabad, Pakistan. 2 Department of Petroleum Engineering, College of Petroleum and Geosciences, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia. 3 To whom correspondence should be addressed; e-mail: [email protected]

with this flow regime are the accurate determination of: (a) liquid flow rate; (b) wellhead pressure; and (c) choke diameter. However, the pressure is usually accurately known through well-calibrated pressure gauges and transmitters; in addition, the choke sizes are also easily determined. Nevertheless, determining the accurate production rate is of utmost importance when it comes to field development, downstream equipment designing, preventing gas/ water coning, and sand production. Consequently, this is achieved by regulating the flow from the well through use of wellhead chok