RU2198285C2 - Method of recovery and transportation of natural gas from flowers and bees gas and gas-hydrate offshore fields - Google Patents

Abstract

FIELD: gas production industry, particularly, methods of offshore recovery of natural gas and its transportation. SUBSTANCE: natural gas is recovered by wells. Recovery of natural gas by wells is carried out periodically with its simultaneous delivery to transportation means where gas is processed into hydrate state. Processing of gas is performed in one group of vessels. Simultaneously, in other group of vessels hydrates of carbon dioxide from wastes of industrial enterprises are decomposed. Produced gas is injected to sea depth to provide for its burial in hydrate state. Processing of recovered gas and decomposition of carbon dioxide hydrates are carried out with utilization of heat balance between them. Produced gas is transported by transportation means. EFFECT: reduced energy consumption, and combination of technologies of natural gas processing into hydrate state and utilization of carbon dioxide wastes of industrial enterprises. 1 dwg

Description

 The invention relates to the gas industry, and in particular to methods of marine production of natural gas and its transport.

 The closest technical solution to the present invention is a method of production and transportation of natural gas from gas and gas hydrate offshore fields [Gudmundsson J. S., Hveding F., Borrehaug A. Frozen Hydrate Compared to LNG. Trondheim, Norwegian Institute of Technology, 1995, p. 9-11, fig. 2-3], including the extraction of natural gas by wells, its processing in a hydrated state and transportation in a mobile vehicle. Gas is processed on an offshore production platform using a special installation, which includes a tank for preparing water for hydrate formation, a refrigerator for producing fine ice from this water, a reactor, a hydrate and water separator, a freezer and a hydrate loader on a mobile vehicle. A heating unit and a unit for preparing and supplying gas to the consumer were built ashore for the reverse process - decomposition of hydrates and drying of gas.

 The known method has the following disadvantages. For the implementation of the known method requires the installation of heavy equipment on the production platform, which makes it inactive and incapable of rapid movement as the depletion of the developed area. When processing natural gas into a hydrated state, it is first necessary to purify the gas, produce hydrate, remove a large amount of heat generated during hydrate formation, compress the hydrate, freeze it and immerse the hydrate frozen in a mobile vehicle, which leads to the loss of a large volume of gas during these operations .

 When creating the invention, the technical problem was solved: reducing energy costs and combining technologies for processing natural gas into a hydrated state and carbon dioxide utilization of industrial waste.

 The solution to this problem is achieved by the fact that in the method of production and transport of natural gas from gas and gas hydrate offshore fields, including the extraction of natural gas by wells, its processing into a hydrated state and transportation on a mobile device, the production of natural gas by wells is carried out periodically with simultaneous supply to a mobile means, and gas processing is carried out on a mobile vehicle in one group of containers with simultaneous decomposition in another group of containers of carbonate hydrates th gas industrial wastes and by pumping the latter on the depth of the sea, providing its disposal in hydrated condition, and processing the extracted gas and the decomposition of carbon dioxide hydrate is carried out using heat balance therebetween.

 This invention is illustrated in the drawing, which shows a diagram of gas production, its processing and transport on a mobile vehicle, including wells 1, the mouths of which are fixed on deep sea platforms 2, mobile tools 3 for processing and transporting natural gas and carbon dioxide from industrial waste, onshore a terminal consisting of a unit for preparing gas for transport 4, delivered by mobile means 3, and pipelines 5 and 6, respectively, for supplying natural gas to a consumer and supplying carbon dioxide waste of industrial enterprises to the vehicle 3.

 The mobile vehicle 3 is a marine vessel with two groups of cylindrical containers vertically arranged in the hold. One group of containers is designed for the current processing of natural gas into a hydrated state, and the other for the decomposition of carbon dioxide hydrates from industrial waste. The buoyancy of the vessel provides a layer of thermal insulation at the bottom, sides and roof of the hold. The vessel’s design also includes a device for mixing water in the hold (water cannon), a device for pumping water for hydrate formation from one tank to another (water pump) and a small compressor for pumping carbon dioxide to the required water depth (near the offshore platform) or residual crude hydrocarbon gas to the onshore gas preparation unit for transport 4 (at the onshore terminal). The bulk of the hydrocarbon gas is pumped using the pressure created by the hydrates themselves during decomposition from heating in the hold.

 The method is as follows.

 In the deep-sea gas (or gas hydrate) field, several small production platforms 2 (“flowers”) are installed on tension supports having berths for ships 3 and a deep-water branch (pipe) for pumping carbon dioxide to a depth of hydrate formation (from 400 m and deeper). On each platform, the mouth of one or more production wells 1 is installed (according to traditional technology) and, after testing, the wells are jammed and preserved until the arrival of vessel 3 ("bees"). The platform does not provide for the stay of technical personnel on it. When the vessel 3 arrives at one of the producing platforms 2, the crew connects the branches of the vessel 3 for hydrocarbon gas (for injection onto the vessel) and for carbon dioxide (for pumping), launches the wells 1, and the gas flows under its own pressure into the free group of tanks, and also in the group of vessel capacities freed from carbon dioxide and water. In advance, devices are started for mixing water inside the vessel 3, a water pump for pumping water with special additives after the decomposition of carbon dioxide hydrates, and a compressor for pumping carbon dioxide into the sea. Mixing the water inside the vessel provides the ability to control the rate of decomposition and hydrate formation by regulating the incoming and outgoing gas flows.

 The formation of hydrates of crude hydrocarbon gas is carried out by injection into containers filled with crude hydrocarbon gas prepared for hydrate formation of water (water with a small amount of surfactants to accelerate hydrate formation). The gas pressure is first created by natural reservoir pressure, and as it falls, a small compressor installed on the vessel 3 is connected. The stock of prepared water is stored on the vessel in a special container. At the same time, in a neighboring group of tanks filled with carbonate hydrate brought from the shore, the decomposition of these hydrates begins, and the gas released under its own pressure or with compression by a small compressor installed on the vessel 3 is pumped through the pipe to the sea to a depth that ensures its burial in hydrated condition. There, the hydrate formed settles on the bottom of the sea under platform 2. The heat exchange between the containers inside the vessel 3, filled with water, is supported by the circulation of water using a small water jet installed in the hold. Since marine hydrate-bearing deposits have low permeability, the production rate of production wells 1 will fall rapidly, therefore, gas production on one platform 2 is carried out periodically. The duration of one period is determined by the pressure at the wellhead: as soon as it decreases to the hydrate formation pressure at a given temperature in the tanks of the vessel 3, a small amount of hydrated dispersant is poured into the well 1 and it is preserved until the next production period, the beginning of which will depend on the rate of pressure recovery at the bottom of the well 1. Vessel 3 is sent to the next production platform 2 located nearby, where the above procedure is repeated. And so from platform to platform, until all groups of tanks (except one) on vessel 3 are filled with hydrate of natural hydrocarbon gas. After that, the vessel 3 is sent to the coastal terminal, where the gas preparation unit for transport 4 is located. Here the reverse process takes place: decomposition of hydrocarbon gas hydrates in some groups of tanks with the simultaneous formation of carbon dioxide hydrates in others according to the method described above. Carbon dioxide is supplied from thermal power plants operating on hydrocarbon fuel through pipes 6. At the gas treatment unit for transport 4, it is supplied to the vessel 3 using a compressor, where it is bound to hydrates. The released crude hydrocarbon gas is supplied to the gas preparation unit for transport 4, where it is purified, dried, separated by known methods, and in its commercial form it is supplied to pipeline 5, through which it is supplied to consumers (to the same power plants).

 As the productive plots are depleted, the production platforms 2 move to other plots not affected by development.

Claims (1)

 A method of producing and transporting gas from gas and gas hydrate offshore fields, including producing natural gas by wells, processing it in a hydrated state and transporting it on a mobile vehicle, characterized in that the production of natural gas by wells is carried out periodically with simultaneous supply to a mobile vehicle, and gas processing carried out on a vehicle in one group of containers with the simultaneous decomposition in another group of containers of carbon dioxide hydrates of industrial waste and pumping the latter to a depth of the sea, ensuring its burial in a hydrated state, moreover, the processing of produced gas and the decomposition of carbon dioxide hydrates is carried out using a heat balance between them.