New Monoethylene-Glycol Sensor Validated by Flow Loop Under Hydrate-Forming Conditions
Authors: Carpenter Chris 
Published: September 2021

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 202375, “Validation of a Novel MEG Sensor Employing a Pilot-Scale Subsea Jumper,” by Asheesh Kumar, The University of Western Australia; Mauricio Di Lorenzo, SPE, CSIRO Energy; and Bruce W.E. Norris, SPE, The University of Western Australia, et al., prepared for the 2020 SPE Asia Pacific Oil and Gas Conference and Exhibition, originally scheduled to be held in Perth, Australia, 20–22 October. The paper has not been peer reviewed.

Online pipeline-management systems provide real-time and look-ahead functionality for production networks. They are limited, however, by a dearth of data with which to inform their predictions. This represents a barrier to a true, high-fidelity digital twin. Greater integration with new sensor technologies is needed to bound model predictions and improve their reliability. In this work, the authors present a novel monoethylene-glycol (MEG) sensing system and validate it in a specially constructed flow loop.

Introduction

Subsea jumpers experience a high probability of hydrate blockages. The most common practice used to avoid hydrate formation in subsea wellhead jumpers essentially is based on the injection of thermodynamic hydrate inhibitors such as MEG and methanol at high flow rates to flush out and inhibit the water pooled in the low spots of the jumper spools. Such hydrate management operations in deep water require adequate planning to minimize unproductive time and may not be feasible in unplanned well shutdowns.

To improve the models implemented in current sensing technologies and explore their potential for new functionalities to detect hydrate formation, measurements under realistic field conditions in a controlled environment are vital. In this work, a flow loop that replicates the geometry of industrial subsea jumpers was deployed to investigate the performance of a new MEG sensor for subsea applications under hydrate-forming conditions. Preliminary baseline experiments were performed at steady state and during gas-restart operations in the absence of any hydrates in the jumper flow loop. Experiments were performed at 64.4°F with nitrogen (N2) gas at 1,200 psig and superficial gas velocity ranges from 0.82 to 2.88 ft/s. The MEG-sensing system’s performance was investigated under hydrate-forming conditions with and without MEG (10–30 wt% in water) in the jumper test section. These experiments were performed at temperatures ranging from 25.2 to 35.6°F.

Experimental Flow Loop

The flow loop consists of a test section connected to independent gas and liquid injection equipment at the inlet and gas-separation facilities at the outlet, which allows for continuous recirculation of gas and a once-through pass of the liquid. The test section has a complex geometry, with three identical low points (LPs) and two high points. The horizontal length of each low and high points is 12 ft, 10 in., and 7 ft, 7 in., respectively, and total height is 13 ft, 2 in. The test section is equipped with 12 pressure and temperature sensors distributed at regular intervals, a MEG sensor at the second LP, a throttling valve downstream of the first high point to mimic a wellhead choke, and a viewing window at the outlet.