The objective of this work is to measure physical, chemical, mechanical, and hydrologic property changes in sediments containing hydrate, water, and gas subjected to varying stimuli (such as injection of non-methane gases) and conditions like the effects of sediment layering and the effects of relevant gradients (thermal, chemical [salinity or gas chemistry], and capillary pressure) on hydrate behavior and address unknowns in the behavior of hydrate-bearing sediments subjected to dissociation relevant to a planned DOE gas hydrate production test to be conducted on the Alaska North Slope. Tests will evaluate the mechanical properties of hydrate-bearing sediments (HBS) under controlled conditions to provide data sets for comparisons to numerical models. Measurements performed in this project are designed to supplement and support field and numerical simulation investigations to provide benchmark measurements and reality checks. 

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720

Hydrate systems are complex, and simplification is required for laboratory studies to generate conceptual models that can be expressed numerically in order to aid in predicting gas production and mechanical changes of the sediments. A number of recent studies have been performed regarding measuring and interpreting mechanical properties in HBS. Those studies and their results will be considered in test designs for this study.

The purpose of this project is to gain a better understanding of the effects of the behavior of hydrate-bearing systems under some of the conditions that could be expected in the field, particularly under gas production conditions. During gas production, hydrate systems will be subject to thermal (from the endothermal dissociation), capillary (from the multiple phases) chemical (from water freshening and varying gas chemistries), and mechanical (from stress redistribution) influences, and each of these is likely to affect gas production. 

The planned set of tests will evaluate the mechanical properties of  HBS under controlled conditions to provide data sets for comparison to numerical models. Results will be shared with those analyzing the test data and the scientific community, and communication is planned with those analyzing the field test to ensure that tests are on track to answer key questions. The investigated  HBS are intended to model potential energy targets.
 

This lab-based research will help meet the program goals for hydrates by improving the understanding of the processes associated with 1) quantifying relevant processes and influences, 2) aiding in understanding gas production from sediments having a variety of properties, 3) providing a better understanding of hydrate behavior in systems having a natural or imposed gradient, and 4) aiding in understanding mechanical property changes. The results will provide important information for interpreting other laboratory and field tests; quantifying the importance of natural and imposed thermal, chemical, or capillary pressure gradients; and impacts on the hydrological and mechanical behavior of  HBS. Questions asked and answered during this project will be from a reservoir perspective, with the understanding that many nonideal conditions exist.

• Completed designed and initiated testing of lab apparatus for CO₂ hydrate formation
• Initiated investigation of the kinetics of pure CO₂ hydrate formation in sediments and in engineered media
• Developed, and initiated testing of a new CO₂-hydrate simulation capabilities (leveraging LBNL internal software development funding)
• Completed experimental evaluation of Alaska relevant hydrate systems at 60% initial water saturation. Experiments conducted on both the layered Alaska relevant sediment, as well as a mixed one-layer sediment to try to understand the effect of layering
• Improved data analysis methods for all sample types to allow better resolution in results interpretation
• Completed fixes to bring CT scanner back to operational status
• Completed tests examining compaction throughout a sand column (synthetic sample representative of anticipated Alaska test site sediments) 
• Researchers have developed a better understanding of the geomechanical modeling of gas  HBS from the 2nd International Gas Hydrate Code Comparison Study (IGHCC2) and designed lab tests — with aid from the international participants — to provide benchmark data.
• LBNL has built a new apparatus that works within their current gas hydrate lab test systems to quantify geomechanical effects on HBS under a wide range of conditions and hydrate habits.
• The research team has devised a novel technique allowing X-ray computed tomography (CT) measurements by sub-voxel quantification of sample length changes. New approaches to image registration and length quantification were formulated.

Please see the project page for ESD12-011 to view accomplishments from past, related efforts.

Efforts under Budget Period (BP) 4 have been largely completed with initiation of fundamental experiments focused on improving understanding of the diffusion of gas through hydrate systems. BP5 activities initiated in October of 2022 and are focused on experiments to determine and maximize the efficiency of CO₂ hydrate formation. Experiments will include surface-area effect on hydrate formation, and the potential for continuous or cyclical-batch processes to form hydrate for separation processes.

$700,000

$0 

NETL – Kyle Clark (Kyle.Clark@netl.doe.gov)
LBNL – Matthew Reagan (mtreagan@lbl.gov)

Topical Report – Design Information and Description of Measurements [PDF] July, 2019