Paper Number
FC3
Session
Flow Assurance of Crude Oil & Derivatives
Title
Controlled formation and aggregation of hydrate suspensions
Presentation Date and Time
October 15, 2018 (Monday) 10:40
Track / Room
Track 2 / Plaza I
Authors
- Geri, Michela (MIT, Mechanical Engineering)
- Sambath, Krishnaraj (Chevron ETC)
- Venkatesan, Ramachandran (Chevron ETC)
- McKinley, Gareth H. (Massachusetts Institute of Technology)
Author and Affiliation Lines
Michela Geri1, Krishnaraj Sambath2, Ramachandran Venkatesan2, and Gareth H. McKinley1
1Massachusetts Institute of Technology, Cambridge, MA 02139; 2Chevron ETC, Houston, TX
Speaker / Presenter
McKinley, Gareth H.
Text of Abstract
Clathrate hydrates are crystalline cage-like compounds that form when a lattice of hydrogen-bonded water molecules is filled by guest molecules sequestered from an adjacent gas or liquid phase. Understanding hydrate formation and agglomeration is of great importance for flow assurance as hydrate plugs pose a major risk to deepwater production. Being able to easily produce and transport synthetic hydrates is also of great interest given their significant potential as clean energy source and safe option for gas storage. Conventionally, hydrate suspensions are produced from water-in-oil emulsions seeded with few ice/hydrate particles to promote hydrate nucleation&growth. This method often results in long and variable nucleation induction times without guaranteeing conversion of all water droplets. Here we describe a new method to rapidly produce hydrate suspensions at ambient pressure by taking advantage of the Rayleigh-Plateau instability to form a monodisperse stream of droplets during the controlled breakup of a water jet. These small drops are immediately quenched into ice particles via immersion in a deeply subcooled reservoir and can be subsequently converted into hydrates with a dramatic reduction in the induction time. By measuring the evolution of the shear viscosity with time, we monitor the process of hydrate formation for different water volume fractions and imposed shear rates. We show that the observed viscosity increase is initially dominated by a change in effective volume fraction that is independent of both water content and applied deformation rate. We also show that the main mechanism underlying this thixotropic response is related to agglomeration of hydrate particles, which can be controlled and tuned by the addition of surfactants and anti-agglomerants. A theoretical analysis based on an existing model for the rheology of attractive suspensions complements our experimental study in understanding the key mediating role of surfactants and the surprising universality of the agglomeration process.