The super-saturation condition has to be provided to form gas hydrates. Consequently, the prediction of the guest molecule fraction in the aqueous phase is crucial in the study of the gas hydrate kinetics. In the present work, several experiments were carried out in a semi-batch reactor in order to determine the mole fraction of methane and ethane during gas hydrates formation (growth stage...

Gas hydrates in sub-seabed sediments is an unexploited source of energy with estimated reserves larger than those of conventional oil. One of the methods for recovering methane from gas hydrates involves injection of Carbon Dioxide (CO2), causing the dissociation of methane and storing CO2. The occurrence of gas hydrates offshore Portugal is well known associated to mud volcanoes in the Gulf of...

In this work and in order to consider theoretically the effect of gas hydrates on the mechanical properties of their host sediments, hydrate fraction was introduced as a state variable in the framework of a Critical State model. For the proposed model, the process of de-structuration and softening of natural clay was considered as a proxy for the gas-hydrate-bearing-sediments behaviour. The dev...

Seismic analyses of methane hydrate data from the Blake Outer Ridge indicate high Pwave velocity and anomalously low S-wave velocity in sediments containing methane hydrates. In an attempt to explain this observed P-wave and S-wave velocity structure at the transition from gas to hydrates, the effect of different hydrate models on elastic moduli and velocities are explored. After construction o...

margins contain vast reserves of gas hydrate, a frozen form of natural gas that is embedded in cold, near-seafloor strata. Published estimates suggest that the energy represented by gas hydrate may exceed the energy available from conventional fossil fuel by a factor of 2 or more. Understanding marine hydrate systems has become critical for long-term worldwide energy planning. Groups in several...

Natural gas hydrate, also known as combustible ice, and mainly composed of methane, is identified as a potential clean energy for the 21st century. Due to its large reserves, gas hydrate can ease problems caused by energy resource shortage and has gained attention around the world. In this paper, we focus on the exploration and development of gas hydrate as well as discussing its status and fut...

Gas Hydrates are widely distributed in the near surface at high latitudes and many ocean bottoms. Our laboratory measurements help calibrate the seismic and well log data that are used to ascertain the in situ distribution of hydrates. Ultrasonic velocities are measured in unconsolidated sand specimen under thermobaric conditions comparable to those found in shallow oceanic or permafrost region...

Gas hydrates are crystalline ice-like solid materials enclosing gas molecules inside. The possibility of the presence of gas hydrates with amino acids in the universe is of interest when revealing the potential existence of life as they are evidence of a source of water and organic precursors, respectively. However, little is known about how they can naturally coexist, and their crystallization...

For almost 30 years. serious interest has been directed toward natural gas hydrate, a crystalline solid composed of water and methane, as a potential (i) energy resource, (ii) factor in global climate change, and (iii) submarine geohazard. Although each of these issues can affect human welfare, only (iii) is considered to be of immediate importance. Assessments of gas hydrate as an energy resou...

[1] Huge quantities of CH4 are stored in marine sediment in the form of methane hydrate, bubbles, and dissolved CH4 in pore water. Here I discuss the various pathways for methane to enter the ocean and atmosphere, including: (i) Methane hydrate dissolution or dissociation as it rises through seawater. The dissociation rate can be 2 to 3 orders of magnitude greater than the dissolution rate. (ii...