Experimental Investigation of Early Leak Detection in Offshore Multiphase Flow Pipelines Using Non-Invasive Electrical Resistance Tomography

Abstract

Prompt and reliable detection of pipeline leaks is vital for human safety, the economy, the environment, and corporate reputation. The objective of the current analysis is to investigate the effectiveness of noninvasive Electric Resistance Tomography (ERT) in detecting and locating leaks in offshore oil and gas pipelines under various multiphase flow scenarios and compare it with real-time visualization data. A flow loop apparatus with a diameter of 0.0508 m and a length of 6.9 m is used for conducting experiments. Water is employed as a representative Newtonian fluid, while air is utilized to simulate the gas phase in different scenarios. The experiments were conducted on different flow rates of liquid (150-383.50 kg/min) and gas (10-50 g/min). The three distinct leak sizes (3, 2, 5 and 1.8 mm) are introduced together to replicate offshore leak scenarios in this study. For the same gas input scenario (10 g/min), increasing the liquid mass flow rate from 150 to 383.50 kg/min reduces the system's gas phase composition in ERT from 4.16% to 1.44% which is about 65.3% less, highlighting the influence of liquid flow rate. Furthermore, the ERT measurement revealed that when increasing the gas phase quantities (10 to 50 g/min) under constant liquid conditions (173.5 and 244.8 kg/min), more gas pockets were identified in ERT observations, resulting in higher gas phase compositions. Moreover, in the case of leak conditions, it provides relatively fewer quantities of air voids in the pipeline when compared to no leak cases, indicating the applicability of ERT in leak scenarios. The correlation between liquid flow rate and gas phase composition indicates the potential for optimizing pipeline operations by adjusting flow rates to minimize gas phase presence. The applicability of ERT in detecting leaks, especially in offshore scenarios, is promising for water (Newtonian fluid), however, further experimentation is needed to assess its performance for non-Newtonian fluids, multiple leak sizes and leak locations which are often encountered in real-world pipelines.