Unsupervised machine learning model for predicting anomalies in subsurface safety valves and application in offshore wells during oil production

Abstract

Predicting oil well behavior regarding the integrity of its equipment during production and anticipating behavioral changes and anomalies are among the main challenges in oil production. In this context, this study focuses on the development of predictive models for real-time monitoring of well behavior using sensor data from production wells. An unsupervised Novelty and Outlier Detection model has been introduced with a specific focus on predicting instances of unexpected subsurface safety valve closures in subsea wells. This model effectively classifies anomalies observed in these systems by leveraging real-world pressure and temperature data sourced from published literature. The methodology involves the implementation of a floating window for assembling training and test sets. Additionally, a comprehensive investigation is conducted into the impact of hyperparameters and the model’s threshold value (cp threshold). The results highlight the effectiveness of the developed model, observed through the accuracy achieved around 99.9% in predicting spurious closure events of the Downhole Safety Valve. On the same dataset, previous works reported 99.9% accuracy by using long short-term memory (LSTM) autoencoder, 87.1% by using random forest, and 60% with the Decision Tree method. Looking at F1-SCORE values, the developed model performs the best, followed by the LSTM model, both of which are significantly superior to the Decision Tree and random forest models. Furthermore, the model’s applicability is validated through testing in ultradeep water subsea wells within the pre-salt area of the Santos Basin. The significance lies in the potential for this research to enhance anomaly prediction in offshore wells, consequently reducing the costly interventions due to equipment malfunctions. Timely detection and corrective actions, facilitated by the model, can mitigate production loss and safeguard well integrity, addressing critical concerns in the oil and gas industry.