MRI insight on multiphase flow in hydrate-bearing sediment and development mechanism of hydrate seal

作     者：Guo-Jun Zhao Ming-Jun Yang Xin Lv Jia-Nan Zheng Yong-Chen Song 

作者机构：Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of EducationDalian University of TechnologyDalian 116024LiaoningChina CNOOC Research Institute Co.LtdBeijing100027China Shanghai Institute for Advanced StudyZhejiang UniversityShanghai201203China 

出 版 物：《Petroleum Science》 (石油科学（英文版）)

年 卷 期：2023年第20卷第6期

页      面：3854-3864页

核心收录：

学科分类：0820[工学-石油与天然气工程] 08[工学] 0817[工学-化学工程与技术] 0818[工学-地质资源与地质工程] 082002[工学-油气田开发工程] 0702[理学-物理学] 

基　　金：supported by the National Key Research and Development Plan of China(2021YFC2800902) the National Natural Science Foundation of China(52206076,U19B2005) the Fundamental Research Funds for the Central Universities of China(DUT21ZD103) the Opening Fund of MOE Key Laboratory of Ocean Energy Utilization and Energy Conservation(LOEC-202204). 

主　　题：Gas hydrate Gas-water migration Underlying gas Hydrate seal Pore difference MRI 

摘      要：Gas and water migration through the hydrate-bearing sediment are characteristic features in marine gas hydrate reservoirs worldwide.However,there are few experimental investigations on the effect of water-gas flow on the gas hydrate reservoir.In this study,gas-water migration in gas hydrate stability zone(GHSZ)was investigated visually employing a high-resolution magnetic resonance imaging(MRI)apparatus,and the formation of hydrate seal was experimentally investigated.Results revealed that normal flow of gas-water at the low flow rate of 1–0.25 mL/min will induce the hydrate reformation.Conversely,higher gas-water flow rates(at 2–0.5 and 4–1 mL/min)need higher reservoir pressure to induce the hydrate reformation.In addition,the hydrate reformation during the gas-water flow process produced the hydrate seal,which can withstand an over 9.0 MPa overpressure.This high overpressure provides the development condition for the underlying gas and/or water reservoir.A composite MRI image of the whole hydrate seal was obtained through the MRI.The pore difference between hydrate zone and coexistence zone produces a capillary sealing effect for hydrate seal.The hydrate saturation of hydrate seal was more than 51.6%,and the water saturation was more than 19.3%.However,the hydrate seal can be broken through when the overpressure exceeded the capillary pressure of the hydrate seal,which induced the sudden drop of reservoir pressure.This study provides a scientific explanation for the existence of high-pressure underlying gas below the hydrate layer and is significant for the safe exploitation of these common typical marine hydrate reservoirs.