There are numerous gas hydrate reserves all over the world, especially in permafrost regions and ocean environments. The abundance of gas hydrate reserves is estimated to be more than twice of the combined carbon of coal, conventional gas and petroleum reserves. These hydrate deposits hold significant amount of energy which can make hydrate a sustainable energy resource. The comprehensive research on the properties and formation of methane hydrates is paramount to ensure efficient and effective exploration and development of hydrate reserves. Natural gas is mostly distributed for different purposes through pipelines or pressure vessels such as dry gas, compressed gas or liquefied gas, which means transporting natural gas creates serious safety concerns because methane is highly flammable and almost impossible to detect any leak without using odorant. Alternatively, natural gas can be stored and transported as gas hydrate turns solid or slurry. Gas hydrate can be stored at equilibrium conditions with either saturation temperature or pressure. The equilibrium conditions are influenced by the cost and weight of storage vessel. Hydrate can be transported either as slurry or solid depending on the location of target or destination. The slurry form is usually a better option for distance of approximately 2500 mile or less while the solid form can be used for distances of roughly 3500 miles or more. The paper examines the properties, formation and benefits of gas hydrate. The suitability of gas hydrate as a sustainable energy resource and the possibility of using gas hydrate for the transportation and storage of natural gas (methane) are also stated. Natural gas transportation and storage as gas hydrate will create effectively and efficiently alternative bulk gas transportation and storage for future use of the gas.
Gas flaring is one of the major problems in the world. It consumes useful natural resources and produces harmful wastes, which have negative impacts on the society. It is one of the most tedious energy and environmental problems facing the world today. It is a multi-billion dollar waste, a local environmental catastrophe and environmental problem which has persisted for decades.From the year 1996-2010.25 million ft 3 of natural gas was flared (NNPC). This is equivalent to losing about 12,967.952 × 10 12 Btu of energy that would have been used to generate power or converted to other forms of energy. In 2015, the World Bank estimated that 140 billion cubic meters of natural gas produced with oil is flared annually, mostly in developing countries without gas processing infrastructures, or other means of utilizing the produced gas. It is widely known that flaring or even, venting of gas contributes significantly to greenhouse gas emissions, with negative impacts on the environment. Thus, alternative solutions to reduce or utilize the quantity of gas flared are crucial issues. Therefore, the need to study and provide detailed understanding of these alternative solutions to gas flaring is important. This paperoutlined the harmful effects of gas flaring and the different possible alternatives to gas flaring. The proposed alternative solutions are gas for secondary oil recovery, feedstock for petrochemical plants, domestic uses, LNG & CNG, as well as energy conservation by storing as gas hydrate for future use or other purposes. Gas hydrate is stable above the freezing point of water and sufficiently high pressure. It is relatively stable under its saturation temperature and pressure and also much denser than normal ice. This property of gas hydrate can be experimentally investigated and capitalized on, to effectively store natural gas as hydrate for energy conservation instead of flaring the gas wastefully. The alternative solutions will convincingly reduce and in the nearest future stop gas flaring globally.
The analysis of wellbore stability in deepwater gas wells is vital for effective drilling operations, especially in deepwater remote areas and for modern drilling technologies. Wellbore stability problems usually occur when drilling through hydrocarbon formations such as shale, unconsolidated sandstone, fractured carbonate formations and HPHT formations with narrow safety mud window. These problems can significantly affect drilling time, costs and the whole drilling operations. In deepwater gas wells, there is also the possible of gas hydrate problems because of the low temperature and high pressure conditions of the environment as well as the coexistence of gas and water inside the wellbore. These hydrates can block the mud line, surface choke line and even the BOP stack if no hydrate preventive measures are considered. In addition, the dissociation of these hydrates in the wellbore may gasify the drilling fluid and reduce drilling mud density, hydrostatic pressure, change mud rheology and cause wellbore instabilities. Traditional wellbore stability analysis considered the formation to be isotropic and assumed that the rock mechanical properties are independent of in-situ stress direction. This assumption is invalid for formations with layers or natural fractures because the presence of these geological features will influence rock anisotropic properties, wellbore stress concentration and failure behavior. This is a complicated phenomenon because the stress distribution around a wellbore is affected by factors such as rock properties, far-field principal stresses, wellbore trajectory, formation pore pressure, reservoir and drilling fluids properties and time. This research work reviews the major causes of wellbore stability problems in deepwater gas wells and outlines different preventive measures for effective drilling operation, because real-time monitoring of drilling process can provide necessary information for solving any wellbore stability problems in a short time.
Hydrate formation can cause serious problems in hydrocarbon exploration, production, and transportation, especially in deepwater environments. Hydrate‐related problems affects the integrity of the deepwater platforms, leads to equipment blockages, and also increases operational costs. In order to solve these problems, salts are used as thermodynamic inhibitors and also mixed with the drilling fluids in most drilling processes. A comprehensive understanding of hydrate formation in aqueous salt solutions is vital to overcome these problems. Statistical thermodynamic models are commonly used to predict hydrate formation conditions in different aqueous solutions. However, these models involve rigorous computations and are restricted to certain conditions. They give inaccurate predictions of hydrate equilibrium conditions for high‐temperature, high‐pressure, and high‐salinity systems. Therefore, it is paramount to develop a simple‐to‐use and reliable prediction tool. In this work, an empirical correlation is developed and successfully used to predict the equilibrium conditions of ethane, propane, and isobutane hydrates in pure water and aqueous solutions of sodium chloride, potassium chloride, calcium chloride, and magnesium chloride. Experimental data on hydrate formation conditions for these components are regressed and a generalized correlation is obtained. The predictions in this work show excellent agreement with all the experimental data in the literature.
Clathrate hydrates are non-stoichiometric compounds of water and gas molecules coexisting at relatively low temperatures and high pressures. The gas molecules are trapped in cage-like structures of the water molecules by hydrogen bonds. There are several hydrate deposits in permafrost and oceanic sediments with an enormous amount of energy. The energy content of methane in hydrate reservoirs is considered to be up to 50 times that of conventional petroleum resources, with about 2,500 to 20,000 trillion m3 of methane gas. More than 220 hydrate deposits in permafrost and oceanic sediments have been identified to date. The exploration and production of these deposits to recover the trapped methane gas could overcome the world energy challenges and create a sustainable energy future. Furthermore, global warming is a major issue facing the world at large and it is caused by greenhouse gas emissions such as carbon dioxide. As a result, researchers and organizations have proposed various methods of reducing the emission of carbon dioxide gas. One of the proposed methods is the geological storage of carbon dioxide in depleted oil and gas reservoirs, oceanic sediments, deep saline aquifers, and depleted hydrate deposits. Studies have shown that there is the possibility of methane gas production and carbon dioxide storage in hydrate reservoirs using the injection of carbon dioxide and nitrogen gas mixture. However, the conventional hydrocarbon production methods cannot be used for the hydrate reservoirs due to the nature of these reservoirs. In addition, thermal stimulation and depressurization are not effective methods for methane gas production and carbon sequestration in hydrate-bearing sediments. Therefore, the gas replacement method for methane production and carbon dioxide storage in clathrate hydrate is investigated in this paper. The research studies (experiments, modeling/simulation, and field tests) on CO2/N2 gas mixture injection for the optimization of methane gas recovery in hydrate reservoirs are reviewed. It was discovered that the injection of the gas mixture enhanced the recovery process by replacing methane gas in the small and large cages of the hydrate. Also, the presence of N2 molecules significantly increased fluid injectivity and methane recovery rate. In addition, a significant amount of free water was not released and the hydrate phase was stable during the replacement process. It is an effective method for permanent storage of carbon dioxide in the hydrate layer. However, further research studies on the effects of gas composition, particle size, and gas transport on the replacement process and swapping rate are required.
The dissociation conditions of methane hydrate in high concentration aqueous solutions of NaCl, KCl, and CaCl2 are reported in this work. A total of 80 sets of H–L–V equilibrium data of methane hydrate in aqueous solutions of NaCl (9.45–23.71 wt %), KCl (13.93–21.88 wt %), and CaCl2 (13.78–35.50 wt %) were measured at the temperature range of (273.65–291.85) K and the pressure range of (5.43–65.12) MPa. A modified step-heating method with high efficiency was employed in the measurements. Good agreements were recorded when the measured data were compared with the literature data and the predictions of well-known software. A generalized correlation was developed for the equilibrium conditions of methane hydrate in aqueous salt solutions. Excellent agreement was recorded in the comparison of the prediction and the experimental data in the literature and those measured in this work.
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