Jitendra Sangwai

Energy is an essential commodity for the survival and socioeconomic development of the human race. The energy supply sector primarily comprises of industrial, commercial, and domestic applications. The foremost challenges faced by the energy supply sector are growing consumption levels, limited accessibility, environmental concerns, viz-a-viz, climate change, and pollution of water and air resources. As conventional resources of energy have started to decline and are expected to get exhausted by 2040, the main focus has been shifted to unconventional sources [1]. In this category, natural gas resources such as gas hydrate, shale gas, coal bed methane will provide tremendous potential for meeting the demand. Gas hydrates are ice-like crystalline substance formed by a framework of water and natural gas molecules. Recent exploration programs by various agencies such as United States Geological Survey (USGS), National Gas Hydrate Program (India), Japanese Methane Gas Hydrate R&D have proved that massive amount of gas hydrate deposits lying across marine settings and permafrost environments. Hydrate deposits are currently estimated to be 5 × 1015 m3 of methane gas [2]. If this untapped resource of energy becomes feasible for the economic production, it could increase natural gas reserves to multifold. Moreover, this would be considerably greater than the total amount of all fossil fuels together. As reported by USGS, gas hydrates hold more than 50% of the entire world’s carbon. It has been estimated that commercial production of methane from 15% of natural gas hydrate can fulfill the energy requirement of the entire world for next 200 years [3]. Hence, natural gas hydrates are considered to be the vital sustainable energy resource. Many pilot production tests have been completed and are underway to recover methane from gas hydrate deposit across the world [4]. Preliminary studies and pilot tests have shown promising results in terms of methane recovery from natural gas hydrates by employing methods such as thermal stimulation, depressurization, inhibitor injection. Ongoing gas hydrate research programs throughout the world and advances in technology will certainly help to cater any technical challenges in order to potentially harness the huge amount of energy stored in the form of natural gas hydrates.

Understanding the formation and dissociation behavior of methane gas hydrate in marine sediments is one of the important precursors for methane gas production from the hydrate deposits. The phase behavior of gas hydrates is influenced by the presence of sediments, composition of salts and water present in it. Krishna–Godavari (KG) Basin in India is one such reservoir which has a huge potential of methane gas hydrates. Here, we have investigated the phase equilibria, and the kinetics of methane hydrate formation, and dissociation in the presence of pure water, and in aqueous solution of 10 wt% (KG) basin sediment. We observed that the phase equilibrium conditions of methane hydrate in presence of 10 wt% sediment solution got shifted to slightly higher pressures at given temperature as compared to that in the bulk phase. It has also been observed that more number of methane gas molecules are consumed in 10 wt% sediment solution in the initial 30 minutes of time than in the pure water system, revealing the promotion effect of sediment surface. The number of moles of methane gas released during the dissociation of hydrate has found to be lesser in sediment solution than in pure water at any given time after initial 55 min of the start of dissociation.