Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Prediction of Permeability for Hydrate-bearing Sediments with Coexisting Hydrate Growth Habits
Yunwei Shi1, Xianqi Luo1, *, Jin Xu1, 2
1 School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University

Shanghai, China
2 Department of Arms Training, Officers College of PAP

Guangzhou, Guangdong, China

capacity through the porous medium, which is determined by theconnectivity of the medium and the size of the pores. The effect ofdifferent hydrate saturation and growth habits on the pore-scalepermeability of HBS can be expressed in terms of the normalized
permeability, defined by the ratio of the permeability of a porous
medium containing hydrates to the permeability of a hydrate-freemedium. The normalized permeability can be estimated in thefollowing ways: (i) laboratory experiments based on synthetic HBS(Masuda et al., 1997; Kumar et al., 2010; Seol and Kneafsey, 2011; Aiet al., 2017; Choi et al., 2020); (ii) in situ experiments using remodeled
hydrate-bearing samples (Nimblett and Ruppel, 2003; Johnson et al.,2011; Santamarina et al., 2010); (iii) in situ field investigations(Kleinberg, 2003; Collett et al., 2011; Song et al., 2013); (iv) numericalsimulations using synthesized or conceptual porous media (Sakamoto etal., 2010; Dai and Seol, 2014; Wang et al., 2015; Kang et al., 2016;
Chen et al., 2018; Hou et al., 2018; Ji et al., 2019). In the absence of
reliable experimental data and equipment for in situ measurements,
numerical methods are more often used to study the permeability
properties during hydrate generation and decomposition.
The aforementioned studies analyzed the permeability of HBS under
the influence of a single hydrate growth habit and reservoir mode, using
theoretical models, indoor tests or numerical simulations. However,most of the numerical models are based on theoretical models of
microscopic pore structure and simplified pore network models of HBS,
and actual reservoirs have been scarcely studied in research, whichcannot fully reflect the natural complex pore structure characteristics
under the influence of hydrates. The main factors considered arehydrate-related properties, which are only applicable to a certain typeof porous media. In addition, most studies focus on the influence ofpore-filled hydrate and coating hydrate separately, while thecoexistence of multiple hydrate growth habits is observed during thetest. Therefore, it is necessary to study the influence of porecharacteristics, hydrate saturation and microscopic mode of hydrateassignment on the permeability of HBS, based on the three-dimensional
pore structure of various hydrate-bearing layers.
This paper establishes the 3D conceptual model of porous media andthe reconstruction model of natural HBS to analyze the permeability
characteristics of HBS by considering the influence of different

ABSTRACT
Natural gas hydrate is considered to be a huge, efficient and clean
energy. Understanding the mechanism of fluid flow in hydrate-bearing
sediments (HBS) plays an important role in guiding hydrate production.
This paper constructs the 3D pore structure of HBS considering theinfluencing factors such as porosity, particle size and pore throat ratio,
including theoretical model and natural sediments. The multi-point
geostatistical method is used to duplicate the proportion and spatial
distribution relationship between phases, and the porous media of HBS
under different hydrate growth habits and hydrate saturation isestablished. Finally, the Lattice Boltzmann Method (LBM) is used tosimulate the pore scale seepage.

KEY WORDS: Natural gas hydrate; Lattice Boltzmann Method;
porous medium; permeability; multi-point geostatistical method.

INTRODUCTION
Natural gas hydrate (gas hydrate for short) is an ice and crystalline cagecompound formed by water and natural gas under high pressure andlow temperature (Sloan and Carolyn, 2008), which is mainly distributedin marine sediments and permafrost area. The growth habit of gas
hydrate in the pore space has the following four modes: coating, porefilling, skeleton-supported, and particle-contact (Qin et al., 2015;
Boswell and Collett, 2011; Lee and Collett, 2009). According toresearchers' estimation, the total resources of gas hydrate in the world
converted into methane gas are about 1.8×1016~2.1×1016 m3, withorganic carbon reserves equivalent to twice of the world's fossil fuels
discovered (coal, oil and natural gas, etc.) (Paull and Dillon, 2001). The
amount of marine gas hydrate is very huge, more than 100 times that ofterrestrial permafrost (Paull and Dillon, 2001). Therefore, gas hydrate,
especially marine gas hydrate, is considered to be a promising energy inthe 21st century.
During hydrate extraction, the permeability of HBS is not only
influenced by hydrate growth habits and saturation, but also related tothe size, shape and distribution of particles and pores, as well as
porosity. Absolute permeability is used to measure the fluid flow583