Peculiarities of geological and thermobaric conditions for the gas hydrate deposits occurence in the Black Sea and the prospects for their development

The actuality has been revealed of the necessity to attract the gas hydrate deposits of the Black Sea into industrial development as an alternative to traditional gas fields. This should be preceded by the identification and synthesis of geological and thermobaric peculiarities of their existence. It was noted that the gas hydrates formation occurs under certain thermobaric conditions, with the availability of a gas hydrate-forming agent, which is capable of hydrate formation, as well as a sufficient amount of water necessary to start the crystallization process. The gas hydrate accumulation typically does not occur in free space – in sea water, but in the massif of the sea bed rocks. The important role in the process of natural gas hydrates formation is assigned to thermobaric parameters, as well as to the properties and features of the geological environment, in which, actually, the process of hydrate formation and further hydrate accumulation occurs. It was noted that the source of formation and accumulation of the Black Sea gas hydrates is mainly catagenetic (deep) gas, but diagenetic gas also takes part in the process of gas hydrate deposits formation. The main component of natural gas hydrate deposits is methane and its homologs – ethane, propane, isobutane. The analysis has been made of geological and geophysical data and literature materials devoted to the study of the offshore area and the bottom of the Black Sea, as well as to the identification of gas hydrate deposits. It was established that in the offshore area the gas hydrate deposits with a heterogeneous structure dominate, that is, which comprises a certain proportion of aluminosilicate inclusions. It was noted that the Black Sea bottom sediments, beginning with the depths of 500 – 600 m, are gassy with methane, and a large sea part is favourable for hydrate formation at temperatures of +8...+9ºC and pressures from 7 to 20 MPa at different depths. The characteristics of gas hydrate deposits are provided, as well as requirements and aspects with regard to their industrialization and development. It is recommended to use the method of thermal influence on gas hydrate deposits, since, from an ecological point of view, it is the safest method which does not require additional water resources for its implementation, because water intake is carried out directly from the upper sea layers. A new classification of gas hydrate deposits with a heterogeneous structure has been developed, which is based on the content of rocks inclusions in gas hydrate, the classification feature of which is the amount of heat spent on the dissociation process

3-D numerical modeling of methane hydrate deposits

Within the German gas hydrate initiative SUGAR, we have developed a new tool for predicting the formation of sub-seafloor gas hydrate deposits. For this purpose, a new 2D/3D module simulating the biogenic generation of methane from organic material and the formation of gas hydrates has been added to the petroleum systems modeling software package PetroMod®. T ypically, PetroMod® simulates the thermogenic generation of multiple hydrocarbon components including oil and gas, their migration through geological strata, and finally predicts the oil and gas accumulation in suitable reservoir formations. We have extended PetroMod® to simulate gas hydrate accumulations in marine and permafrost environments by the implementation of algorithms describing (1) the physical, thermodynamic, and kinetic properties of gas hydrates; and (2) a kinetic continuum model for the microbially mediated, low temperature degradation of particulate organic carbon in sediments. Additionally, the temporal and spatial resolutions of PetroMod® were increased in order to simulate processes on time scales of hundreds of years and within decimeters of spatial extension. As a first test case for validating and improving the abilities of the new hydrate module, the petroleum systems model of the Alaska North Slope developed by IES (currently Shlumberger) and the USGS has been chosen. In this area, gas hydrates have been drilled in several wells, and a field test for hydrate production is planned for 2011/2012. The results of the simulation runs in PetroMod® predicting the thickness of the gas hydrate stability field, the generation and migration of biogenic and thermogenic methane gas, and its accumulation as gas hydrates will be shown during the conference. The predicted distribution of gas hydrates will be discussed in comparison to recent gas hydrate findings in the Alaska North Slope region

Transport- reaction modeling of marine gas hydrate deposits- global results

We have developed a multi-1D numerical model of gas hydrate formation and dissolution processes in anoxic marine sediments and, by this model, we have estimated the new global gas hydrate inventory (BURWICZ E. B. et al., 2011). The reaction-transport model contains various chemical compounds (solid organic carbon, dissolved methane, inorganic carbon, and sulfates, gas hydrates, and free methane gas). The rates of POC degradation, anaerobic methane oxidation, sulfate reduction, and methanogenesis are kinetically controlled. Gas hydrate stability zone (GHSZ) is defined as a combination of pressure, temperature, and (to a smaller degree) salinity conditions. The lower boundary of the GHSZ is defined as the intersection of gas hydrate and methane gas solubilities. The diffusion equations are solved using a fully-implicit finite-differences method, while all transport processes are resolved by a Semi-Lagrangian scheme. Global input data sets (1°x1° resolution) were compiled from various oceanographic, geological and geophysical sources. The entire model was implemented in Matlab

Process pattern of heterogeneous gas hydrate deposits dissociation

Purpose. Justification of the effective dissociation process parameters of heterogeneous gas hydrate deposits and elaboration of their classification according to the thermal energy consumption. Methodology. The methodological basis of the conducted complex research is the analysis and synthesis of literary sources, devoted to studying the peculiarities and thermobaric properties of gas hydrates, analytical calculations and laboratory experiments on the thermal energy consumption for the efficient decomposition of gas hydrates, experimental studies of the hydrate formation process and gas hydrate deposits of the mottled structure dissociation. Findings. The parameters of formation and stable gas hydrate occurrence in natural environment, which should be taken into account when developing gas hydrate deposits, are substantiated. The existing classification of gas hydrate deposits in sedimentary rocks is analyzed. The regularities of the gas hydrate deposits dissociation process and methane gas production, depending on the percentage of rock intercalations content, are established. The volumes of analysis zones and gas output from heterogeneous gas hydrate deposits are determined. The amount of thermal energy that is necessary to be consumed to produce 1000 m3 of hydrated gas during the gas hydrate deposits development, is calculated. Originality. It is established that the thermal energy consumption on the dissociation process in order to obtain methane gas varies with a parabolic dependency with an increase in the rock intercalations proportion in the gas hydrate deposit. A new classification of gas hydrate deposits, based on the content of rock intercalations and the amount of spent thermal energy for gas hydrate dissociation, has been developed. Practical value. The results of studies with sufficient accuracy for practical application may be used in the development of the Black Sea gas hydrate deposits in order to obtain natural gas. The revealed dependencies of the methane gas output on the rock intercalation share are a tool for determining the effective application of technologies for the gas hydrate deposit development.Мета. Обґрунтування параметрів ефективного процесу дисоціації неоднорідних газогідратних покладів і розробка їх класифікації за затратами теплової енергії. Методика. Методичною основою проведених комплексних досліджень є аналіз і узагальнення літературних джерел, присвячених вивченню особливостей і термобаричних властивостей газових гідратів, аналітичні розрахунки й лабораторні екс- перименти щодо затрат теплової енергії для ефективного розкладання газогідратів, експериментальні дослідження процесу гідратоутворення й дисоціації газогідратних покладів неоднорідної структури. Результати. Обґрунтовані параметри формування й стабільного існування газогідратів у природних умовах, що необхідно враховувати при розробці газогідратних родовищ. Проаналізовані існуючі класифікації покладів газових гідратів в осадових породах. Встановлені закономірності процесу дисоціації газогідратних покладів і одержання газу метану в залежності від процентного вмісту породних включень. Визначені об’єми зон розкладання й вихід газу із неоднорідних газогідратних покладів. Розрахована кількість теплової енергії, що необхідно затратити для одержання 1000 м3 гідратного газу при розробці газогідратних родовищ. Наукова новизна. Встановлено, що затрати теплової енергії на протікання процесу дисоціації для одержання газу метану змінюються за параболічною залежністю зі збільшенням частки породних включень у газогідратному покладі. Розроблена нова класифікація газогідратних покладів за вмістом породних включень і кількістю затраченої теплової енергії на дисоціацію газогідрату. Практична значимість. Результати досліджень із достатньою для практичного застосування точністю можуть використовуватися при розробці газогідратних родовищ Чорного моря з метою отримання природного газу. Виявлені залежності виходу газу метану від частки породних включень є інструментарієм для визначення ефективної області застосування технологій розробки покладів газових гідратів. Ключові слова: газогідратний поклад, неоднорідність, класифікація, породні включення, дисоціація, затрати енергіїЦель. Обоснование параметров эффективного процесса диссоциации неоднородных газогидратных залежей и разработка их классификации по затратам тепловой энергии. Методика. Методической основой проведенных комплексных исследований является анализ и обобщение литературных источников, посвященных изучению особенностей и термобарических свойств газовых гидратов, аналитические расчеты и лабораторные эксперименты по затратам тепловой энергии для эффективного разложения газогидратов, экспериментальные исследования процесса гидратообразования и диссоциации газогидратных залежей неоднородной структуры. Результаты. Обоснованы параметры формирования и стабильного существования газогидратов в природных условиях, что необходимо учитывать при разработке газогидратных месторождений. Проанализированы существующие классификации залежей газовых гидратов в осадочных породах. Установлены закономерности процесса диссоциации газогидратных залежей и получения газа метана в зависимости от процентного содержания породных включений. Определены объемы зон разложения и выход газа из неоднородных газогидратных залежей. Рассчитано количество тепловой энергии, которую необходимо затратить для получения 1000 м3 гидратного газа при разработке газогидратных месторождений. Научная новизна. Установлено, что затраты тепловой энергии на протекание процесса диссоциации для получения газа метана изменяются по параболической зависимости с увеличением доли породных включений в газогидратной залежи. Разработана новая классификация газогидратных залежей по содержанию породных включений и количеству затраченной тепловой энергии на диссоциацию газогидрата. Практическая значимость. Результаты исследований с достаточной для практического применения точностью могут использоваться при разработке газогидратных залежей Черного моря с целью получения природного газа. Выявленные зависимости выхода газа метана от доли породных включений являются инструментарием для определения эффективной области применения технологий разработки залежей газовых гидратов.The presented results were obtained in the framework of the complex implementation of research papers GP-473 “Development of scientific principles of phase transformations of technogenic and natural gas hydrates and creation of the newest technologies of their extraction” (State registration No. 0115U002294) and GP-487 “Scientific substantiation and development of energy saving and low waste technologies of hydrocarbon and mineral raw materials extraction” (State registration No. 0116U008041)

Ab initio molecular dynamics simulations of Aluminum solvation

The solvation of Al and its hydrolyzed species in water clusters has been studied by means of ab initio molecular dynamics simulations. The hexa-hydrate aluminum ion formed a stable complex in the finite temperature cluster simulation of one aluminum ion and 16 waters. The average dipole moment of strongly polarized hydrated water molecules in the first solvation shell of the hexa-hydrate aluminum ion was found to be 5.02 Debye. The deprotonated hexa-hydrate complex evolves into a tetra-coordinated aluminate ion with two water molecules in the second solvation shell forming hydrogen bonds to the hydroxyl groups in agreement with the observed coordination.Comment: 12 pages in Elsevier LaTeX, 5 figures in Postscript, 2 last figures are in color, submitted to Chemical Physics Letter

Stability of Ca-montmorillonite hydrates: A computer simulation study

Classic simulations are used to study interlayer structure, swelling curves, and stability of Ca-montmorillonite hydrates. For this purpose, NPzzT$ and MuPzzT ensembles are sampled for ground level and given burial conditions. For ground level conditions, a double layer hydrate having 15.0 A of basal spacing is the predominant state for relative vapor pressures (p/po) ranging in 0.6-1.0. A triple hydrate counting on 17.9 A of interlaminar distance was also found stable for p/po=1.0. For low vapor pressures, the system may produce a less hydrated but still double layer state with 13.5 A or even a single layer hydrate with 12.2 A of interlaminar distance. This depends on the established initial conditions. On the other hand, the effect of burial conditions is two sided. It was found that it enhances dehydration for all vapor pressures except for saturation, where swelling is promoted.Comment: 8 pages, 9 figure

Dispersion forces stabilise ice coatings at certain gas hydrate interfaces which prevent water wetting

Gas hydrates formed in oceans and permafrost occur in vast quantities on Earth representing both a massive potential fuel source and a large threat in climate forecasts. They have been predicted to be important on other bodies in our solar systems such as Enceladus, a moon of Saturn. CO$_2$-hydrates likely drive the massive gas-rich water plumes seen and sampled by the spacecraft Cassini, and the source of these hydrates is thought to be due to buoyant gas hydrate particles. Dispersion forces cause gas hydrates to be coated in a 3-4 nm thick film of ice, or to contact water directly, depending on which gas they contain. These films are shown to significantly alter the properties of the gas hydrate clusters, for example, whether they float or sink. It is also expected to influence gas hydrate growth and gas leakage