Mahmut Parlaktuna

Effect of an anionic surfactant on different type of hydrate structures

In this study, methane and gas mixture (including 88.17% propane) hydrates were produced from the anionic surfactant solutions of 0.00, 0.01 and 0.05 wt.% to investigate the effect of surfactant on the hydrate formation rate. Hydrate formation rate increases (promotion effect) with surfactant concentration, but the extent of the surfactant effect is closely related with the type of hydrate structure. The increase in the hydrate formation rate of sII type structure is relatively small compared to that obtained with structure sI.

Laboratory for Continuous Production of Natural Gas Hydrates

Abstract: Natural gas hydrate technology is an attractive alternative for storing and transporting natural gas. A high‐pressure laboratory has been built to provide experimental data for use in the design and development of hydrate‐based processes for the oil and gas industry. In the laboratory, hydrate is produced from liquid water‐and water‐in‐oil emulsions‐and injected natural gas mixtures. The hydrate reactor and circulation loop can operate at pressures up to 120 bar and constant temperatures in the range 0–20°C. The hydrate slurry produced can be circulated at up to 100 liter/minute through 4‐m long pipes equipped with differential pressure transducers and flow meters to determine their rheological characteristics under laminar and turbulent flow conditions. The laboratory can also be used for various flow assurance studies.

Effect of Surfactants on Hydrate Formation Rate

Natural gas hydrates exhibit two opposing properties. First, they are considered as a nuisance in oil industry since they plug pipelines requiring costly remedies. Second, there are several possible applications of hydrates such as storage and transportation of natural gas, desalinization of water, and recovery of rare gases. In addition, in situ hydrates are considered to be the commercial energy supply for the future. These two aspects of gas hydrates stimulated hydrate studies from two opposite directions. The studies related to the problematic side of hydrates are trying to find methods for hydrate inhibition. Other studies are exploring for ways to promote hydrate formation. The traditional hydrate inhibitors such as methanol and glycols have been in use for several decades, but as production platforms are becoming more remote within deeper water, use of these chemicals becomes more and more costly. Replacing these traditional thermodynamic inhibitors with a new generation of hydrate inhibitors can lead to very substantial cost savings. Kelland et al . 1 discuss the types and properties of these new generation gas hydrate inhibitors. Surfactants and polymers are classes of chemicals that affect the hydrate formation process and are considered new hydrate inhibitors (Kelland et al . 2 ). These chemicals affect hydrate formation through one of two processes, kinetic inhibition or anti-agglomeration. Although polymers are mainly considered kinetic inhibitors, surfactants exhibit diverse agglomeration characteristics. Kalogerakis et al . 3 investigated experimentally the effect of surfactants on the kinetics of methane hydrate. They reported that surfactants do not influence the thermodynamics; however, they have a strong influence on the kinetics of gas dissolution in the water phase as well as increasing the overall rate of hydrate formation. They also observed that the hydrate particles formed in the presence of the various surfactants exhibit diverse agglomeration characteristics. Urdahl et al . 4 developed an experimental set-up for characterizing of gas hydrate inhibitor efficiency with respect to flow properties and deposition. They reported that the chemicals used in their study are surfactants, polymers, and various patented chemicals. The surfactants among them are known to stabilize water in oil emulsions. These chemicals showed some positive effects, but at concentrations above 1 wt% of the aqueous phase. They did not prevent deposition of hydrates at the water

The use of chemical inhibitors for prevention of calcium carbonate scaling

Abstract An experimental study on calcium carbonate scaling and prevention by chemical inhibitors was carried out in a laboratory model. In order to study the inhibiting capacities of the chemicals, experiments were performed with four different inhibitors by flashing 350 cc of 0.1 M Ca++ solution to atmospheric pressure at a temperature of 144 °C. The partial pressure of C02 was 3.6 MPa. The performances of inhibitors with different concentrations were analyzed in terms of the amount of scale formed. The results showed that the amount of scale was reduced, but not totaly prevented and after a certain inhibitor concentration it increased again which was interpreted as the formation of a pseudo-scale. Then the process was tested with different calcium concentrations in solution and partial pressures of carbon dioxide. Amount of deposited calcite increased with the increase of these two parameters.

Production of l-aspartic acid by biotransformation and recovery using reverse micelle and gas hydrate methods

l-Aspartic acid (l-Asp) was produced using Escherichia coli (ATCC 11303), and its recovery from the reaction mixture was studied using reverse micelle and gas hydrate methods. The effect of initial substrate concentration on l-Asp production was also investigated, and inhibition was shown to occur above 0.75 mol L−1. The values of the kinetic constants were determined as rmax=2.33×10−4 mol L−1 min−1, KM=0.19 mol L−1, and Kss=3.98 mol L−1. The reverse micelle phase used for extraction contained Aliquat-336, 1-decanol and isooctane, and a micro-injection technique was used for extraction of l-Asp. The reverse micelle system is a useful technique for obtaining small particle sizes, which can be used for the synthesis of nanoparticle biomolecules. Recovery of l-Asp from reverse micelles using CO2 hydrates was carried out, giving a recovery of 55%. The formation of CO2 hydrate from the reverse micelle solution breaks the micelle by reducing the amount of water in the micelle structure, thus precipitating the l-Asp.

Natural Gas Hydrate Potential of the Black Sea

The Black Sea is among the regions that have been cited in the literature as having conditions suitable for natural gas hydrate reserves. Russian scientists confirmed by seismic studies that there are five regions in the Black Sea which are highly promising for hydrate formation. In this study, conventional petroleum engineering methods are utilized to estimate the possible amount of gas available in one of the Black Sea Basins.

A Cyclic Steam Injection Model for Gas Production from a Hydrate Reservoir

Thermally efficient production of natural gas from a hydrate reservoir by the use of cyclic steam injection process was modeled. The model was considered as a three-phase process: an injection phase, a soak phase, and a production phase. Using energy and mass balances, heat transfer equations, and steam properties, wellbore heat losses, heat losses to base and cap rock, and heat losses during dissociation were calculated. The radial advance of the hydrate front was tracked during each cycle. The produced gas volume and combustible energy of this gas were compared with the energy of the injected steam to compute energy efficiency of the process. To determine the best possible conditions for gas production from a hydrate reservoir by cyclic injection, the model was tested for a wide range of parameters. Overall thermal efficiency was calculated for different reservoir porosity, reservoir depth, hydrate zone thickness, heat injection rate, and steam injection temperature.

NATURAL GAS HYDRATES AS A CAUSE OF UNDERWATER LANDSLIDES: A REVIEW

Natural gas hydrates occur worldwide in polar regions, normally associated with onshore and offshore permafrost, and in sediment of outer continental margins. The total amount of methane in gas hydrates likely doubles the recoverable and non-recoverable fossil fuels. Three aspects of gas hydrates are important: their fossil fuel resource potential, their role as a submarine geohazard, and their effects on global climate change. Since gas hydrates represent huge amounts of methane within 2000 m of the Earth’s surface, they are considered to be an unconventional, unproven source of fossil fuel. Because gas hydrates are metastable, changes of pressure and temperature affect their stability. Destabilized gas hydrates beneath the seafloor lead to geologic hazards such as submarine slumps and slides. Destabilized gas hydrates may also affect climate through the release of methane, a “greenhouse” gas, which may enhance global warming.

Estimation of Silica Scaling Temperatures of Kizildere Geothermal Field Effluent, Turkey

A computer program, SPECIATION, was developed to determine the detailed composition of an aqueous solution and the concentrations and activities of all species. Once the detailed composition of an aqueous solution is known, it is possible to determine the saturation level of the solution with respect to any mineral, which is silica for this study. Three water samples from the Kizildere geothermal field of Turkey were collected and the chemical analyses of these samples were used as input data in SPECIA TION to determine their detailed composition for obtaining the silica scaling potential of the Kizildere field effluent. The analysis of the silica scaling studies indicate that the pH of the power plant effluent of the Kizildere field increases due to boiling and loss of acid gases (mainly CO 2 ). This increase in pH results with an increase in the solubility of amorphous silica. As a consequence, the silica scaling danger of effluent is carried to lower temperatures, which makes the problem-free temperature range wider.

Hydrate Inhibition with PEO (Poly 2-ethyl-2-oxazoline)

This study is aimed at investigating the effects of a poly 2-ethyl-2-oxazoline-type polymer on the prevention of methane hydrate formation. During the study, seven experiments with low concentrations of poly 2-ethyl-2-oxazoline (0 to 1 wt%) were run in a batch-type reactor. The analysis of the experimental study indicates that poly 2-ethyl-2-oxazoline can be considered as a potential kinetic inhibitor for hydrate formation.