Path-dependent morphology of CH4 hydrates and their dissociation studied with high-pressure microfluidics

Jidong Zhang; Zhenyuan Yin; Saif A Khan; Shuxia Li; Qingping Li; Xiaohui Liu; Praveen Linga

doi:10.1039/d3lc00950e

Path-dependent morphology of CH₄ hydrates and their dissociation studied with high-pressure microfluidics

Lab Chip. 2024 Mar 12;24(6):1602-1615. doi: 10.1039/d3lc00950e.

Authors

Jidong Zhang¹, Zhenyuan Yin¹, Saif A Khan², Shuxia Li³, Qingping Li⁴, Xiaohui Liu¹, Praveen Linga²

Affiliations

¹ Institute for Ocean Engineering, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China. zyyin@sz.tsinghua.edu.cn.
² Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117582, Singapore.
³ School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China.
⁴ State Key Laboratory of Natural Gas Hydrates, Technology Research Department CNOOC Research, Beijing 100192, China.

PMID: 38323341
DOI: 10.1039/d3lc00950e

Abstract

Methane hydrates (MHs) have been considered a promising future energy source due to their vast resource volume and high energy density. Understanding the behavior of MH formation and dissociation at the pore-scale and the effect of MH distribution on the gas-liquid two phase flow is of critical importance for designing effective production strategies from natural gas hydrate (NGH) reservoirs. In this study, we devised a novel high-pressure microfluidic chip apparatus that is capable of direct observation of MH formation and dissociation behavior at the pore-scale. MH nucleation and growth behavior at 10.0 MPa and dissociation via thermal stimulation with gas bubble generation and evolution were examined. Our experimental results reveal that two different MH formation mechanisms co-exist in pores: (a) porous-type MH with a rough surface formed from CH₄ gas bubbles at the gas-liquid interface and (b) crystal-type MH formed from dissolved CH₄ gas. The growth and movement of crystal-type MH can trigger the sudden nucleation of porous-type MH. Spatially, MHs preferentially grow along the gas-liquid interface in pores. MH dissociation under thermal stimulation practically generates gas bubbles with diameters of 20.0-200.0 μm. Based on a custom-designed image analysis technique, three distinct stages of gas bubble evolution were identified during MH dissociation via thermal stimulation: (a) single gas bubble growth with an expanding water layer at an initial slow dissociation rate, (b) rapid generation of clusters of gas bubbles at a fast dissociation rate, and (c) gas bubble coalescence with uniform distribution in the pore space. The novel apparatus designed and the image analysis technique developed in this study allow us to directly capture the dynamic evolution of the gas-liquid interface during MH formation and dissociation at the pore-scale. The results provide direct first-hand visual evidence of the growth of MHs in pores and valuable insights into gas-liquid two-phase flow behavior during fluid production from NGHs.