• Energy Research

The depressurization approach of methane production from a natural gas hydrate reservoir has been identified as the most energy-efficient production approach. However, some of the field-scale studies involving constant pressure depressurization (CPD) did not yield significant success. To address this, the constant rate gas release (CRD) depressurization approach was used to overcome the drawbacks of the CPD approach. The experimental investigations of these methods with and without thermal stimulation (TS) have not yet been investigated in detail for marine clayey hydrate reservoirs formed in seawater to understand their comparative effectiveness for methane gas recovery. Although common production approaches have been studied by many researchers on hydrate-bearing sand sediments, energy recovery from hydrate-rich clayey sediments has not yet been investigated in detail, which form the major dominant hydrate reservoirs of the hydrate resource pyramid across the globe. This work investigates in detail the ...

Understanding the kinetics of carbon dioxide (CO2) hydrate formation in pure water, seawater and porous media aids in developing technologies for CO2 gas storage, carbon capture and sequestration (CCS) and potentially for methane production from methane hydrates. The present work is focused on understanding the kinetics of CO2 hydrate formation in pure water and seawater at an initial formation pressure of 6 MPa (providing a driving force of about 4.0 MPa) and a formation temperature of 276.15 K with 75% water saturation in three silica sand particle sizes (0.16 mm, 0.46 mm and 0.92 mm). The seawater (3.3 wt% salinity) used in the present study is obtained from sea coast of Chennai (India). It is observed that the gas consumption of CO2 in hydrate is more for smaller silica sand particle and decreases as the size of the sand increases. The total gas consumed at the end of the seawater experiment is found to be less than the gas consumed at the end of the pure water experiment. This is due to the fact that salts in seawater act as a thermodynamic inhibitor resulting in lower gas consumption of CO2 in hydrate. The average rate of hydrate formation observed is optimum in 0.46 mm particles and is observed to be higher as compared to 0.16 and 0.92 mm particles over 10 h experimental time. This indicates that 0.46 mm silica sand provides an optimum environment for efficient hydrate formation. The study can be useful to understand the suitability of potential sandstone reservoir for CO2 sequestration in the form of hydrate in the presence of saline formation water.

Abstract Natural gas hydrate is a potential source of methane which needs to be extracted from under the sea bed. For the economic recovery of methane from natural gas hydrates, production approaches such as depressurization, thermal stimulation, and inhibitor injection are being investigated. However, studies involving hydrate-bearing clayey sediments and recovery of methane from such reservoirs are rare. This work investigates in detail the potency of hydrate dissociation methods such as depressurization by constant rate gas release, thermal stimulation and the combination of two for energy recovery from hydrate bearing clayey sediments underlying a free gas zone. Pure water and two different mud samples containing 3 and 5 wt% of bentonite were used for methane hydrate formation and dissociation studies. Thermodynamic study of methane hydrate in the presence of bentonite clay was also conducted for the above two concentrations. No considerable effect of clay on the inhibition or promotion of methane hydrate formation was observed. Initially, methane hydrate formation has been investigated using pure water, 3 and 5 wt% bentonite mud at an initial hydrate formation pressure of 8 MPa and at a temperature of 278.15 K. Subsequently, methane hydrate dissociation experiments were carried out using depressurization, thermal stimulation and their combination. The effect of the rate of gas release on hydrate dissociation by depressurization was investigated using two different rates of 10 mL/min and 20 mL/min. Thermal stimulation experiments were carried out for ΔT = 15 K at the rate of 7.5 K/hr and the results on methane recovery were recorded. The detailed investigation shows that the combination of the two methods is more efficient for methane production than the standalone method in clayey hydrate reservoir. This study provides important insights into the hydrate production methodology from clayey hydrate reservoirs.

A fundamental study on hydrate formation from an equimolar CO2–CH4 gas mixture has been carried out with two focal points: accelerating the kinetics of hydrate formation and enhancing the gas separ...

Surfactants such as sodium dodecyl sulfate (SDS), which are used as kinetic hydrate promoters in various hydrate based technological applications, are facing a serious roadblock toward their commercial utilization as a result of the excessive amount of foam generation, particularly during hydrate dissociation. One of the approaches to alleviate this foam formation is the use of various antifoaming agents which may be employed in combination with surfactants. The possibility of using one such antifoaming agent, a silicone based polymeric surfactant, for hydrate based methane storage, has been explored in the current work through a detailed morphological study. Investigations on the morphology of hydrate formation and dissociation reveal the strong antifoaming activity of the silicone based compound and the optimal ratio in which it should be mixed with a surfactant, specifically SDS, in order to effectively alleviate unwanted foam formation. Further, kinetic data reveal that the generally observed kinetic ...

Abstract Solidified natural gas (SNG) in the form of clathrate hydrates has been considered one of the most promising technologies for natural gas storage and transportation because it is safe and economically feasible compared to liquefied natural gas (LNG) and compressed natural gas (CNG). In this direction, we recently observed that mixed methane tetrahydrofuran hydrates had the ability to store a significant amount of methane gas close to ambient temperature conditions. To further improve the economic feasibility of methane gas storage and transportation process, utilization of saline water was recommended. In the present work, we investigate the morphology of mixed CH4/THF hydrate formation and dissociation in presence of NaCl for the first time. Morphology changes observed during the nucleation, hydrate growth and dissociation of mixed hydrates at two different operating conditions are presented. All the experiments were performed with a stoichiometric concentration of THF (5.56 mol% THF). More over, the gas uptake was also measured and compared with non-salt experiments.

Low-salinity water injection emerges to be a cost-effective and environmentally friendly enhanced oil recovery technique. Furthermore, additives, such as the surfactant and nanoparticles in combina...