The objective of this work is to measure physical, chemical, mechanical, and hydrologic property changes in sediments containing methane 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. This set of 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.
Please see the project page for ESD12-011 to view accomplishments from past, related efforts.
Efforts under Budget Period (BP) 3 are ongoing and are focused on the finalization of some BP2 activities addressing unknowns in the behavior of HBS subjected to dissociation relevant to a planned DOE gas hydrate production test to be conducted on the Alaska North Slope. These activities were significantly delayed due to power outages resulting from California fires, and laboratory curtailment from the Covid-19 in 2020. Following the completion of those tests, researchers have included geomechanical compaction tests of layered samples and will be developing a series of tests based on the information gained as the test sequence continues using a range of hydrate saturations and a limited number of representative sediment compositions.
Topical Report – Design Information and Description of Measurements [PDF] July, 2019