Nav: Home

Natural gas hydrate in the foraminifera

October 11, 2016

Natural gas hydrates are clathrate hydrates that consist of water molecules and natural gas molecules (major constituent: methane). They are mainly distributed along continental slopes of the oceans or permafrost regions on land. Highly saturated hydrate reservoirs may be ideal alternative energy resources, which makes them an important target area for the exploitation and utilization of natural gas hydrates. Generally, influenced and restricted by the grain size of the sediments, natural gas hydrates are mainly found in the coarse sands, while in fine-grained sediments, the hydrate occurrence is rarely occurs, or the saturation of the gas hydrates would be relatively low. However, among drilling projects in 2007 in the Shenhu area, South China Sea (SCS), the average sand content in the hydrate reservoir was only around 1.4%-4.24%, the hydrate saturation was as high as 20%-40%. While related to the supply of gas source and the tectonic activities, this result may also be attributed to the abundant foraminifera shells in the SCS sediments

The samples used in this study were obtained from Shenhu area, SCS, and provided by Guangzhou Marine Geological Survey during voyage HY-2006-3. It was located in E 115°12.52363?N 19°48.40299? where the water depth is 1,554 meters. The seafloor sediments were collected with gravity piston core. Although these samples did not contain natural hydrates, they were obtained near the location where hydrate samples were drilled in 2007 (Figure 1). Because the geological backgrounds between these two kinds of samples were basically the same, so the samples analyzed in this study are considered as representative of sediments of the hydrate reservoir.

About 10 g SCS samples were dispersed in water, the foraminifera shells in the samples were selected and divided into three groups by size (>150μm, 63-150μm, <63μm). The abundance of foraminifera in the SCS sediments was relatively high, and almost all the foraminifera were planktonic. In addition, most of the foraminifera is coarse-grained (>150 μm).

Surface and inner structures of the foraminifera shells selected from the SCS sediments were studied by SEM and X-ray CT. The foraminifera shells displayed as a single sphere or multi-chamber structure. The surfaces of the shells showed numerous micro-pores (6-8 μm), among which, some pores were filled with sediments, while most of them connected the chambers of the shells to the outside space. most foraminifera shells are still effective pore space providing an ideal place for hydrate growth and accumulation. It can also partially explain the high saturation of hydrate in the fine-grained SCS sediments. By statistically analyzing the number of voxels within the grayscale range that represented the inner pores of the foraminifera in the region, the effective volume of pores inside the foraminifera was up to 18.5% of the total volume, which indicates that the presence of foraminifera shells increases the porosity of the SCS sediments effectively.

The SCS sediments consisted primarily of silt and sand, and the pores between different grains were tiny and filled with clays. Because of the limited image resolution, only the hydrate distribution in the foraminifera chambers (pores inside the grains) could be observed; in turn, so it was difficult to identify tiny hydrate crystals dispersed between fine grains of the sediments in CT images. The hydrates grew inside the foraminifera and occupied partial spaces of the gas and liquid. The volume of the hydrates was greater than the corresponding liquid volume. Before the formation of hydrates, only a small amount of water was present inside some foraminifera shells. With hydrates accumulating over time, the liquid and methane gas mitigated towards the inner space of the foraminifera shells via the mouth and the micro-pores in the shell walls. Except in some of the foraminifera shells filled with other materials, hydrates contacted with the inner walls of the foraminifera shells directly.
See the article: Li C F, Hu G W, Zhang W, Ye Y G, Liu C L, Li Q, Sun J Y. 2016. Influence of foraminifera on formation and occurrence characteristics of natural gas hydrates in fine-grained sediments from shenhu area, South China Sea. Science China Earth Sciences, doi:10.1007/s11430-016-5005-3

Science China Press

Related Water Articles:

Water, water, nowhere
Researchers at the University of Pittsburgh's Swanson School of Engineering have found that the unusual properties of graphane -- a two-dimensional polymer of carbon and hydrogen -- could form a type of anhydrous 'bucket brigade' that transports protons without the need for water, potentially leading to the development of more efficient hydrogen fuel cells for vehicles and other energy systems.
Advantage: Water
When water comes in for a landing on the common catalyst titanium oxide, it splits into hydroxyls just under half the time.
What's really in the water
Through a five-year, $500,000 CAREEER Award from the National Science Foundation, a civil and environmental engineering research group at the University of Pittsburgh's Swanson School of Engineering will be developing new DNA sequencing methods to directly measure viral loads in water and better indicate potential threats to human health.
Jumping water striders know how to avoid breaking of the water surface
When escaping from attacking predators, different water strider species adjust their jump performance to their mass and morphology in order to jump off the water as fast and soon as possible without breaking of the water surface.
Water, water -- the two types of liquid water
There are two types of liquid water, according to research carried out by an international scientific collaboration.
Just add water? New MRI technique shows what drinking water does to your appetite, stomach and brain
Stomach MRI images combined with functional fMRI of the brain activity have provided scientists new insight into how the brain listens to the stomach during eating.
UM researchers found shallow-water corals are not related to their deep-water counterparts
A new study led by scientists at the University of Miami Rosenstiel School of Marine and Atmospheric Science found that shallow-reef corals are more closely related to their shallow-water counterparts over a thousand miles away than they are to deep-water corals on the same reef.
Saline water better than soap and water for cleaning wounds, researchers find
Researchers found that very low water pressure was an acceptable, low-cost alternative for washing out open fractures, and that the reoperation rate was higher in the group that used soap.
UTA research predicting lake levels, moving water to yield better data for water providers
A University of Texas at Arlington environmental engineer is creating an integrated decision support tool for optimal operation of water supply systems that will allow water providers to make better decisions about when to turn on pumps to transfer water from one reservoir system to another and when to release water downstream from the reservoirs.
Surfing water molecules could hold the key to fast and controllable water transport
Scientists at UCL have identified a new and potentially faster way of moving molecules across the surfaces of certain materials.

Related Water Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...