The Gas Hydrate Potential of the Eastern Mediterranean Basin

Gas hydrate exploration studies have increased substantially since last decade. Gas hydrate reservoirs are commonly found in the marine environment and permafrost. Studies related to natural gas hydrates in the Mediterranean Basin are rare compared to those released on the continental margins of the United States of America, Japan, India, China and Korea. This study provides an evaluation of the gas hydrate potential of the Mediterranean Basin using available literature data such as scientific drilling data (Ocean Drilling Program Leg 160 and Leg 161), sediment data, geothermal data, geochemical data, gas seepage data, mud volcano data etc., It is shown that there is a high producible gas hydrate potential (~ 98.16 standard trillion cubic meter) in the Mediterranean Basin. The Eastern Mediterranean basins have the highest gas hydrate potential due to its high amount of source gas potential and lower geothermal gradient compared to those in the Western Mediterranean.Publisher's Versio

Scale-Up Operations for Biogas Production:Analysis on Critical Factors Governing Large-Scale Operations

Anaerobic digestion (AD) is a unique process where different microbial species decompose organic materials in the absence of oxygen and has been widely practiced in full-scale facilities all over the world. Several AD techniques have been applied to convert livestock manures, wastewaters, and solid lignocellulosic waste into biogas. Despite the progress on the engineering of AD systems, several challenges exist for the economically and environmentally efficient way to recover carbon in the form of renewable biogas fuel. The complexity of the challenges poses constraints into the understanding of the factors associated to the scale-up of the AD operations. This study aims to review the critical factors of biogas plant project development

ADVANCES IN CRYOGENIC FRACTURING OF COALBED METHANE RESERVOIRS WITH LN2

Coalbed methane (CBM) is a significant unconventional natural gas resource existing in matrix pores and fractures of coal seams and is a cleaner energy resource compared to coal and crude oil. To produce CBM, stimulation operations are required, given that the coal permeability is generally too low. Hydraulic fracturing is the most widely used technology for reservoir stimulation; however, there are a few challenging issues associated with it, e.g., huge water consumption. In the past decade, the use of liquid nitrogen (LN2) as a fracturing fluid has been intensively studied for stimulating CBM reservoirs, achieving considerable progress in understanding fracturing mechanisms and optimizing fracturing techniques. This paper presents a thorough review of experimental design and observations, modeling procedures and results, field applications, and published patents. Existing studies are divided into five different groups for discussion and comparison, including immersion tests, injection tests, jet drilling tests, numerical modeling, and field applications. Based on the comprehensive evaluation of the outcomes, it is obvious that cryogenic fracturing using LN2 is a promising eco-friendly fracturing technique that can effectively enhance coal rock permeability to increase the production of CBM

KINETIC ANALYSIS OF METHANE HYDRATE FORMATION WITH BUTTERFLY TURBINE IMPELLERS

Heat generation during gas hydrate formation is an important problem because it reduces the amount of water and gas that become gas hydrates. In this research work, we present a new design of an impeller to be used for hydrate formation and to overcome this concern by following the hydrodynamic literature. CH4 hydrate formation experiments were performed in a 5.7 L continuously stirred tank reactor using a butterfly turbine (BT) impeller with no baffle (NB), full baffle (FB), half baffle (HB), and surface baffle (SB) under mixed flow conditions. Four experiments were conducted separately using single and dual impellers. In addition to the estimated induction time, the rate of hydrate formation, hydrate productivity and hydrate formation rate, constant for a maximum of 3 h, were calculated. The induction time was less for both single and dual-impeller experiments that used full baffle for less than 3 min and more than 1 h for all other experiments. In an experiment with a single impeller, a surface baffle yielded higher hydrate growth with a value of 42 108 mol/s, while in an experiment with dual impellers, a half baffle generated higher hydrate growth with a value of 28.8 108 mol/s. Both single and dual impellers achieved the highest values for the hydrate formation rates that were constant in the full-baffle experiments

Deneysel koşulların doğal gaz hidrat oluşumuna etkileri.

Natural gas hydrates (NGH) are proposed as gas storage and transportation media owing to their high gas content and long-term stability of hydrate crystal structure at common refrigeration temperatures and atmospheric pressure. Technically feasible, cost efficient hydrate production is one of the crucial items of the whole chain of storage and transportation of gas by means of NGH technology. This study investigated the effects of types of impellers and baffles, and the use of promoters on natural gas hydrate formation. Up-pumping pitched blade turbine (PBTU) and Rushton turbine (RT) were the two types of impellers tested. The reactor was equipped with different designs of baffles: full, half and surface baffles, or no baffles. In total 48 experiments were completed with different impeller – baffle combinations. Single (PBTU or RT), dual (PBTU/PBTU or RT/RT) and dual-mixed (PBTU/RT or RT/PBTU) use of impellers with full (FB), half (HB), surface (SB) and no baffle (NB) combinations formed two sets of 24 experiments. The first set was completed with the use of pure methane as hydrate forming gas and in the second set methane – propane mixture (95% - 5%) was used. Experimental data was analyzed in terms of induction time, hydrate formation rate, overall power consumption, hydrate productivity and conversion of water to hydrate. In addition, split fraction of methane and propane in free gas and solid hydrate during hydrate formation from mixture gas is determined. The reactor was operated in batch mode in all the experiments. Single impeller experiments with methane showed that Rushton turbine has better performance than up-pumping pitched blade turbine, for all kind of baffles. Use of dual impellers, either the same type or mixed, produced similar results of single impeller. The initial hydrate formation rate is generally higher with the use of Rushton turbine, but the decline rate of hydrate formation was also high compared to up-pumping pitched blade turbine (PBTU). The higher amount of hydrate formed at the gas-water interface initially restricts the mass transfer between gas and water phases and results in a higher decline in the formation rate of hydrate. The other fact causing the decline in hydrate formation rate is the exothermic nature of hydrate formation. Hydrate formation process by gas mixtures become more complex because of different partition of gas components in free gas and solid hydrate phases. Propane is consumed more if hydrate is formed from a gas mixture of methane – propane. This fact brings another complexity of varying hydrate equilibrium curve during hydrate formation. As propane is consumed, hydrate equilibrium pressure gets higher for the given process temperature. Aqueous solutions of amino acids tested in this study showed shorter induction time and generally higher hydrate formation rates compared to distilled water. This indicates a potential of finding hydrate promoters among these amino acids.Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Petroleum and Natural Gas Engineering

Examination of methane hydrate formation by the use of dual impeller combinations

© 2021, Akadémiai Kiadó, Budapest, Hungary.The kinetics of methane gas hydrates formation was obtained by different dual impeller (DI) experiments with full baffle (FB) at 42.5 bar pressure and 2 °C temperature. There were 18 (dual and dual mixed) experiments by the use of pitched blade turbine upward trending (PBTU), pitched blade turbine downward trending (PBTD), rushton turbine (RT) and new impeller design trapezoid turbine in upward trending and down ward trending, TTU and TTD respectively. There were estimations of induction time, duration of hydrate formation, rate of hydrate formation, hydrate formation rate constant, hydrate yield and power consumption. The experiments with radial flow in the upper part of shaft showed better outcomes compared to other combinations for dual impellers in hydrate yield, rate of hydrate formation and hydrate formation rate constant

Examination of behavior of lysine on methane (95%)-propane (5%) hydrate formation by the use of different impellers

Hydrate formation characteristics and hydrodynamic behavior have been investigated for mixture of methane-propane hydrate formation with pure water and with the amino acid of lysine 1.5 wt% at 24.5 bars and 2 degrees C. There were total 12 experiments with full and no baffle estimating the induction time, rate of hydrate formation, hydrate productivity and power consumption. The outcomes showed that radial flow experiments with radial flow have better behavior compared to mixed flow ones due to better interaction between gas and liquid. Furthermore, lysine experiments formed hydrates more quickly compared to pure water experiments showing that lysine functions as promoter and not as inhibitor. RT experiments consume more energy compared to PBT ones, while induction time is always smaller in RT experiments compared to PBT ones

Investigation of gas seepages in Thessaloniki mud volcano in the Mediterranean Sea

Gas seepages are commonly observed in marine environment. Especially, gas seepages due to anthropogenic gas hydrate dissociation are big concerns recently. In the Eastern Mediterranean Sea, Thessaloniki mud volcano was detected. Gas hydrate stability conditions in this mud volcano is very fragile. For this reason, in this study, gas seepages were predicted by using HydrateResSim at different seafloor temperature increments varying from 1 to 5 degrees C and different sediment permeability values varying from 0.1 mD to 5mD in Thessaloniki mud volcano. Both the effect of temperature increment (above 1 degrees C increment) and the increase in permeability cause faster gas hydrate dissociation. The gas seepages on the seafloor of Thessaloniki mud volcano was investigated in this study by using the bubble rise theory. It was found that the effect of gas bubble diameter is high on the height of gas flare in the study area. The effect of permeability and lithology near seafloor on gas release after gas hydrate dissociation is huge. Generally, in Thessaloniki MV, clays are dominant so it is advantageous for environment because even if gas hydrate dissociates, free gas reaches to the seafloor slowly. Moreover, since the next 100 years, it is expected that temperature will increase by +2 degrees C on the seafloor of Thessaloniki MV. It was indicated that gas release will be obvious if temperature increment is above 1 degrees C in this area according to the numerical simulations with HydrateResSim

The Effect of Experimental Conditions on Methane (95%)-Propane (5%) Hydrate Formation

In the present study, the effect of different kinds of impellers with different baffles or no baffle was investigated. Up-pumping pitched blade turbine (PBTU) and Rushton turbine (RT) were the two types of impellers tested. The reactor was equipped with different designs of baffles: full, half and surface baffles or no baffles. Single (PBTU or RT) and dual (PBTU/PBTU or RT/RT) use of impellers with full (FB), half (HB), surface (SB) and no baffle (NB) combinations formed two sets of 16 experiments. There was estimation of rate of hydrate formation, induction time, hydrate productivity, overall power consumption, split fraction and separation factor. In both single and dual impellers, the results showed that RT experiments are better compared to PBTU in rate of hydrate formation. The induction time is almost the same since we are deep in the equilibrium line while hydrate productivity values are higher in PBTU compared to RT experiments. As general view RT experiments consume more energy compared to PBTU experiments

Kinetic Analysis of Methane-Propane Hydrate Formation by the Use of Different Impellers

In the present study, the effect of different kinds of impellers with different baffles or no baffle was investigated. Up-pumping pitched blade turbine (PBTU) and Rushton turbine (RT) were the two types of impellers tested. The reactor was equipped with different designs of baffles: full, half and surface baffles, or no baffles. Single (PBTU or RT) and dual (PBTU/PBTU or RT/RT) use of impellers with full (FB), half (HB), surface (SB), and no baffle (NB) combinations formed two sets of 16 experiments. The first group of experiments was close to the equilibrium line (P = 26.5 bars and T = 8.5 6 C), and the second group was deep in the equilibrium line (P = 24.5 bars and T = 2 degrees C). There was estimation of rate of hydrate formation, induction time, hydrate productivity, overall power consumption, split fraction, and separation factor. In both single and dual impellers, the results showed that RT experiments are better compared to PBTU in the rate of hydrate formation. The induction time is almost the same because we are deep in the equilibrium line while, hydrate productivity values I are higher in PBTU compared to RT experiments. As a general view, RT experiments consume more energy compared to PBTU experiments