This project seeks to bring new understanding of the coupled hydrologic, thermodynamic, and geomechanical processes that control the outcome of applying production technologies to natural gas hydrate bearing reservoirs for the purpose of recovering methane economically and at commercial scales. 

Pacific Northwest National Laboratory (PNNL), Richland, WA

Hydrate systems in geologic media are multiple phase systems, in which the potential for both mobile and immobile phases occupy the same pore space, with the potential mobile phases being aqueous, gas, and nonaqueous liquid, and the potential immobile phases being ice and hydrate. Gas hydrates form at high pressures and low temperatures, and the stability envelope for natural gas hydrates span the triple-point of water, complicating the thermodynamics of hydrate systems via phase transitions, appearances, and disappearances. For example, a hydrate bearing formation, stable at temperatures above freezing, could yield ice formations with strong depressurization, resulting in hydrate dissociation and cooling. Hydrate structures vary across their host geologic settings, from large concretions in suboceanic muds to connected, pore-filling bodies in subarctic sandstones. The geomechanical reaction of a hydrate-bearing formation to the dissociation process depends on the contribution of the hydrate structure to the mechanical properties of the formation. Production of natural gas hydrates from geologic reservoirs is controlled by coupled processes, each with inherent complexities. 

This project will investigate the numerically and experimentally coupled hydrologic, thermodynamic, and geomechanical processes that dominate the production of natural gas hydrates from geologic accumulations. Production technologies will include both conventional (such as depressurization, thermal stimulation, and inhibitor injection) and unconventional (such as nitrogen injection, air injection, and former swapping). Production of natural gas hydrates from geologic reservoirs is controlled by coupled processes, each with inherent complexities.

This project will bring new understanding of the coupled hydrologic, thermodynamic, and geomechanical processes that control the outcome of applying production technologies to natural gas hydrate bearing reservoirs for the purpose of recovering methane economically and at commercial scales. Numerical simulation provides scientists and engineers with analytical tools for investigating the behavior of hydrate systems, incorporating coupled processes in the governing and constitutive equations.

Budget Period (BP) 5

•  Initiation of activities under BP 5 have been delayed.

BP 4

• Completed and verified performance of the parallel version of the Geomechanics (GEOMECH) module responsible for poro-elastic geomechanics. 
• Completed the development and verification of STOMPX-HYDT-KE which is a parallel version of the STOMP hydrate code.

BP 3

• Completed initial simulations of production from Unit B via depressurization for the proposed Alaska Hydrate Production Test site using core and nuclear magnetic resonance (NMR) based permeabilities. 
• Completed efforts to enable the the execution of the STOMP-HYDT-KE simulator with injection and production wells.

BP 2

• Led the conclusion of the 2nd International Gas Hydrate Code Comparison Study (IGHCCS2) with the submission of a manuscript to the Journal of Marine and Petroleum Geology (White et al., 2020). This study focused on the modeling of coupling thermal-hydrological-thermodynamic processes with geomechanical processes.
• Continued collaborative research with KIGAM in support of its objectives of developing gas hydrate production technologies for reservoirs in the Ulleung Basin of the Korea East Sea.

BP 1 

• Continued development of CH4-O2-N2 gas hydrate modeling capabilities.
• Lead the 2nd International Gas Hydrate Code Comparison Study (IGHCCS2) participants through a series of benchmark problems involving coupled flow, transport, thermodynamics, and geomechanics and contributed PNNL solutions to four of the five problems.
• Initiated development of a publication to capture results of the IGHCCS2.

Please see the project page for FWP 65213 to view accomplishments from previous related efforts.

Efforts remaining under BP 4 include completing the coupled well model for injection and production which will allow 3D domain simulations of the Alaska North Slope production testing. At the completion of BP 4, researchers will initiate efforts for BP 5, focused on new fundamental research for numerically investigating schemes for creating stable CO2 gas hydrate in subsurface reservoirs at a commercial scale.  

All DOE Funding
Total Funding to Date: $540,000

NETL – NETL Federal Project Manager – Kyle Clark (kyle.clark@netl.doe.gov)
PNNL – Mark White (mark.white@pnnl.gov)