JP2006045128A - Method for decomposing methane hydrate and apparatus for decomposing the same - Google Patents
Method for decomposing methane hydrate and apparatus for decomposing the same Download PDFInfo
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- JP2006045128A JP2006045128A JP2004229000A JP2004229000A JP2006045128A JP 2006045128 A JP2006045128 A JP 2006045128A JP 2004229000 A JP2004229000 A JP 2004229000A JP 2004229000 A JP2004229000 A JP 2004229000A JP 2006045128 A JP2006045128 A JP 2006045128A
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- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 title claims abstract description 138
- 238000000034 method Methods 0.000 title claims abstract description 37
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 374
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 49
- 239000000284 extract Substances 0.000 claims description 2
- 238000012544 monitoring process Methods 0.000 claims description 2
- 238000011084 recovery Methods 0.000 abstract description 9
- 238000007796 conventional method Methods 0.000 abstract description 2
- 239000007789 gas Substances 0.000 description 51
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 8
- 229910002092 carbon dioxide Inorganic materials 0.000 description 5
- 239000001569 carbon dioxide Substances 0.000 description 5
- 230000003247 decreasing effect Effects 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000006837 decompression Effects 0.000 description 3
- 238000011161 development Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 238000011065 in-situ storage Methods 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 238000004868 gas analysis Methods 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000004898 kneading Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000013535 sea water Substances 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 241000220317 Rosa Species 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- OQHNYZYFESQLHN-UHFFFAOYSA-N molecular oxygen;hydrate Chemical compound O.O=O OQHNYZYFESQLHN-UHFFFAOYSA-N 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- XTQHKBHJIVJGKJ-UHFFFAOYSA-N sulfur monoxide Chemical class S=O XTQHKBHJIVJGKJ-UHFFFAOYSA-N 0.000 description 1
- 229910052815 sulfur oxide Inorganic materials 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/0099—Equipment or details not covered by groups E21B15/00 - E21B40/00 specially adapted for drilling for or production of natural hydrate or clathrate gas reservoirs; Drilling through or monitoring of formations containing gas hydrates or clathrates
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
Description
本発明は、メタンハイドレートの分解方法及び装置に関するものである。 The present invention relates to a method and apparatus for decomposing methane hydrate.
ガスハイドレートは、水分子が作る籠状の格子の中にゲスト分子であるメタンや二酸化炭素等のガスが取り込まれたガス水和物であり、氷状の固体物質の形態をとる。
ゲスト分子としてメタンが取り込まれたメタンガスハイドレートは、天然に広く分布し新エネルギーとして注目を集めている。メタンガスハイドレートは、永久凍土地帯や、大陸棚近くの海底下に広く分布する。最近、経済産業省のメタンガスハイドレート開発国家プロジェクトが開始されており、２１世紀の新エネルギー資源として利用される可能性が高まっている。これは埋蔵量が多く、十分に期待に答えることができると考えられることによる。資源量を検討している研究者の試算によれば、全世界のメタンガスハイドレートの埋蔵量は、陸域で概ね数十兆ｍ3、海域で数千兆ｍ3 に及ぶという。これは世界の天然ガスの確認埋蔵量の数十倍以上に相当する量である。
メタンガスハイドレートは低温高圧の条件下で安定に存在する。海底に存在する場合には、メタンガスハイドレートは低温高圧の安定な条件下にある。これからメタンを生産しようとする場合は、海底のメタンガスハイドレートが存在する所或いはそれを採り出そうとしている所で、メタンガスと水に分解し、メタンを採りだすことが必要となる。図1は、メタンガスハイドレートと窒素および酸素ハイドレートの相平衡条件を示す（Sloan）。低温高圧の安定領域にあるメタンハイドレートを、分解領域の条件に導いてメタンハイドレートを分解する場合には、減圧法または加熱法により条件を分解領域にすることが考えられる。カナダマリックのメタンガスハイドレート産出試験を行った際のプレス発表においても、減圧法と加熱法で行ったことが報告されている。この加熱法では80℃の熱水を用いて、分解領域の条件としている。同様に減圧法では減圧下の分解条件を採用するものである。しかしながら、減圧法、及び加熱法では、コスト面、技術面での問題が解決されていない。他の分解法には海水を注入する方法がある。この方法の場合には、海水の注入の温度が低いこと、浸透率が十分ではないなどの問題点が指摘されている。
又、二酸化炭素で置換する方法（特許文献１ 特開平６−７１１６１号、特開２０００−６１２９３号）がある。この方法では二酸化炭素が固化することが問題とされ、二酸化炭素による置換には効率の低いことが問題とされている。ガスハイドレート層近傍にガス遮蔽壁を設け高温蒸気を注入する方法（特許文献２ 特開平１０−３１７６８６９号）が報告されている。また、水や砂を混合して練り合わせたスラリ-を高速噴流体で供給する方法がある（特許文献３ 特開２００３−２１４０８２号）。この方法は、水や砂を混合して練り合わせたスラリ-を高速噴流体で供給することが大掛かりな装置となり、この点が問題点である。
メタンガスハイドレートの分解のためには、安定で大量に存在し、かつ供給しやすい媒体を用いる、新規な方法及びその装置の開発が望まれている。
The gas hydrate is a gas hydrate in which a gas such as methane or carbon dioxide, which is a guest molecule, is taken in a cage-like lattice formed by water molecules, and takes the form of an ice-like solid substance.
Methane gas hydrate, in which methane is incorporated as a guest molecule, is widely distributed in nature and is attracting attention as a new energy. Methane gas hydrate is widely distributed under the permafrost and under the sea floor near the continental shelf. Recently, the Ministry of Economy, Trade and Industry's methane gas hydrate development national project has started, and the possibility of being used as a new energy resource in the 21st century is increasing. This is due to the fact that the reserves are large enough to meet expectations. According to calculations by researchers who are investigating the amount of resources, the world's methane gas hydrate reserves are roughly several tens of trillion m 3 in land and several thousand trillion m 3 in sea. This is equivalent to more than tens of times the world's confirmed reserves of natural gas.
Methane gas hydrate exists stably under conditions of low temperature and high pressure. When present on the ocean floor, methane gas hydrate is under stable conditions of low temperature and high pressure. In order to produce methane from now on, it is necessary to decompose methane gas and water and extract methane at the place where the methane gas hydrate exists on the seabed or where it is going to be extracted. FIG. 1 shows the phase equilibrium conditions of methane gas hydrate and nitrogen and oxygen hydrate (Sloan). When methane hydrate in the stable region of low temperature and high pressure is introduced to the conditions of the decomposition region to decompose methane hydrate, it is conceivable that the conditions are changed to the decomposition region by a decompression method or a heating method. It was reported in the press announcement during the Canadian Malic methane gas hydrate production test that the depressurization method and the heating method were used. In this heating method, hot water of 80 ° C. is used as a condition for the decomposition region. Similarly, the decompression method employs decomposition conditions under reduced pressure. However, the decompression method and the heating method have not solved the problems in terms of cost and technology. Other decomposition methods include injecting seawater. In the case of this method, problems such as low seawater injection temperature and insufficient permeability have been pointed out.
Further, there is a method of substituting with carbon dioxide (Patent Document 1, JP-A-6-71161, JP-A-2000-61293). In this method, solidification of carbon dioxide is a problem, and low efficiency in substitution with carbon dioxide is a problem. There has been reported a method in which a gas shielding wall is provided in the vicinity of a gas hydrate layer and high temperature steam is injected (Patent Document 2, Japanese Patent Laid-Open No. 10-3176869). Further, there is a method of supplying a slurry obtained by mixing and kneading water and sand with a high-speed jet fluid (Patent Document 3 Japanese Patent Application Laid-Open No. 2003-214082). In this method, a large-scale apparatus is required to supply a slurry obtained by mixing and kneading water and sand with a high-speed jet fluid. This is a problem.
In order to decompose methane gas hydrate, it is desired to develop a novel method and apparatus using a medium that is stable, present in large quantities, and is easy to supply.
本発明の課題は、大量に存在し、供給しやすく、安定な媒体を供給することにより地中に存在するメタンガスハイドレートを分解する新規な方法及び装置を提供することである。 An object of the present invention is to provide a novel method and apparatus for decomposing methane gas hydrate present in the ground by supplying a stable medium that exists in large quantities and is easy to supply.
本発明者らは、安定した相平衡条件にあるメタンガスハイドレート層に空気を注入し、メタンガスハイドレート層が分解領域となるようにして前記ハイドレートの分解反応によりメタンガスを取り出して回収すること、このメタンガスハイドレート層の圧力が一定となるようにして前記ハイドレートの分解反応によりメタンガスを取り出して回収するため、メタンガスハイドレート層に空気を供給することにより前記分解領域となるように維持しつつメタンガスハイドレートを分解させてメタンガスを取り出すことにより、分解反応を継続して、利用しようとしているメタンガスハイドレートを水とメタンガスに分解できることを見出して本発明を完成させた。 The present inventors inject air into a methane gas hydrate layer under stable phase equilibrium conditions, and take out and recover methane gas by the hydrate decomposition reaction so that the methane gas hydrate layer becomes a decomposition region. The methane gas hydrate layer is maintained at a constant pressure by supplying air to the methane gas hydrate layer so that the pressure of the methane gas hydrate layer is constant and methane gas is taken out and recovered by the decomposition reaction of the hydrate. By decomposing methane gas hydrate and extracting methane gas, it was found that the methane gas hydrate to be used can be decomposed into water and methane gas by continuing the decomposition reaction and completed the present invention.
本発明によれば、以下の方法が提供される。
（１）低温高圧下にあるメタンガスハイドレートを分解させてメタンガスを取り出す方法において、相平衡状態にあるメタンガスハイドレート中に空気を送入し、メタンガスハイドレート層が分解領域となるようにしてガスを放出させることによりメタンガスハイドレート層の分解反応によりメタンガスを取り出すことを特徴とするメタンガスハイドレートを分解してメタンガスを取り出す方法。
（２）前記分解領域となるようにしてガスを放出させることによりメタンガスハイドレート層の分解反応によりメタンガスを取り出す操作により、前記分解領域を一定に維持しつつメタンガスハイドレートを分解させてメタンガスを取り出すことを特徴とする前記（1）記載のメタンガスハイドレートを分解してメタンガスを取り出す方法。
（３）前記相平衡状態にあるメタンガスハイドレートは図１に示される温度圧力の関係を有するものであり、空気を送入し、メタンガスハイドレートの原位置条件（温度278〜288K、圧力7〜25MPa）で分解領域に保たれていることを特徴とする前記（1）又は（2）記載のメタンガスハイドレートを分解してメタンガスを取り出す方法。
（４）低温高圧下にあるメタンガスハイドレートを分解してメタンガスを取り出す装置において、メタンガスハイドレートが蓄えられている部分、メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段及びメタンガスハイドレートが分解されて発生するメタンを回収する回収手段を有し、メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段及びメタンガスハイドレートが分解されて発生するメタンを回収する回収手段がプラットホーム上に設置されていることを特徴とする低温高圧下にあるメタンガスハイドレートを分解してメタンガスを取り出す装置。
（５）前記メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段が、メタンガスハイドレートが蓄えられている部分に設けられている温度センサーにより分解過程を監視する手段及びメタンガスハイドレートが蓄えられている部分を一定の圧力に維持するために必要な空気量を算出できる空気量供給手段を有することを特徴とする前記（４）記載の低温高圧下にあるメタンガスハイドレートを分解してメタンガスを取り出す装置。
According to the present invention, the following method is provided.
(1) In the method of decomposing methane gas hydrate under low temperature and high pressure to extract methane gas, air is sent into the methane gas hydrate in a phase equilibrium state so that the methane gas hydrate layer becomes the decomposition region. A method of extracting methane gas by decomposing methane gas hydrate, wherein methane gas is extracted by a decomposition reaction of the methane gas hydrate layer by releasing methane.
(2) By releasing the gas so as to be in the decomposition region, and taking out the methane gas by the decomposition reaction of the methane gas hydrate layer, the methane gas hydrate is decomposed and the methane gas is extracted while maintaining the decomposition region constant. The method for extracting methane gas by decomposing the methane gas hydrate as described in (1) above.
(3) The methane gas hydrate in the phase equilibrium state has the relationship of temperature and pressure shown in FIG. 1 and is fed with air, and the in-situ conditions of the methane gas hydrate (temperature 278 to 288 K, pressure 7 to The method of decomposing the methane gas hydrate as described in (1) or (2) above, wherein the methane gas is taken out by being decomposed at 25 MPa).
(4) In a device for decomposing methane gas hydrate under low temperature and high pressure and taking out methane gas, means for supplying a necessary amount of air to a portion where methane gas hydrate is stored, a portion where methane gas hydrate is stored, and It has recovery means for recovering methane generated by decomposition of methane gas hydrate, means for supplying necessary amount of air to the part where methane gas hydrate is stored, and recovering methane generated by decomposition of methane gas hydrate An apparatus for decomposing methane gas hydrate under low temperature and high pressure and taking out methane gas, characterized in that a recovery means for performing the recovery is installed on the platform.
(5) A means for supplying a necessary amount of air to the portion where the methane gas hydrate is stored is a means for monitoring the decomposition process by a temperature sensor provided in the portion where the methane gas hydrate is stored, and methane gas hydrate Decomposing methane gas hydrate under low temperature and high pressure as described in (4) above, having an air amount supply means capable of calculating the amount of air necessary for maintaining the portion where the rate is stored at a constant pressure To extract methane gas.
メタンガスハイドレートの分解方法に空気を供給する本発明は、メタンガスハイドレートを分解してメタンガスを取り出す従来の方法と相違して、確実に又比較的に簡単な設備により行なうことができるものである。具体的には、相平衡論的に安定しているメタンガスハイドレート層に必要量の空気を注入して原位置のメタンガスハイドレートを分解領域となるようにしてメタンガスを取り出すものであり、経済効果は大である。また、メタンガスハイドレート開発だけでなく、中小天然ガス田等で開発計画のあるメタンをハイドレート化して輸送、貯蔵した後に分解して取り出す方法及び装置としても利用できるものである。
以上の方法によれば、地球環境問題の中心的な二酸化炭素やイオウ酸化物の排出量が少ないエネルギー源として注目されているメタン資源を、前記の効率的な方法により量産することができる。
The present invention for supplying air to a method for decomposing methane gas hydrate can be carried out reliably and with relatively simple equipment, unlike the conventional method for decomposing methane gas hydrate and extracting methane gas. . Specifically, the required amount of air is injected into a methane gas hydrate layer that is stable in terms of phase equilibrium, and the in situ methane gas hydrate becomes the decomposition region, and the methane gas is taken out. Is great. In addition to the development of methane gas hydrate, it can also be used as a method and device for decomposing and extracting methane, which has been planned for development in small and medium natural gas fields, etc., hydrated, transported and stored.
According to the above method, it is possible to mass-produce methane resources, which are attracting attention as an energy source that emits less carbon dioxide and sulfur oxides, which are a global environmental problem, by the above-described efficient method.
図２を用いて本発明の装置を説明する。
本発明の低温高圧下にあるメタンガスハイドレートを分解してメタンガスを取り出す全体装置（１）において、メタンガスハイドレートが蓄えられている部分（２）、メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段（３）及びメタンガスハイドレートが分解されて発生するメタンを回収する回収手段（４）を有し、メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段及びメタンガスハイドレートが分解されて発生するメタンを回収する回収手段がプラットホーム（５）上に設置されている。
The apparatus of the present invention will be described with reference to FIG.
In the overall apparatus (1) for decomposing methane gas hydrate under low temperature and high pressure according to the present invention and taking out methane gas, the necessary amount in the part (2) where methane gas hydrate is stored and the part where methane gas hydrate is stored Means for supplying the required amount of air, and means for supplying the necessary amount of air to the portion where the methane gas hydrate is stored And a recovery means for recovering methane generated by the decomposition of methane gas hydrate is installed on the platform (5).
メタンガスハイドレートが蓄えられている部分（２）は、大陸棚などのメタンが蓄えられている海底下地中部分である。この部分は絶えず自然の状態であり、かつ一定温度に保たれている。特定地域によりその温度には変動が見られるが、一般的には２７８〜２８８Ｋ程度に保たれていると考えてよい。この温度の詳細は、予め測定されている。又、海底下の地中にあることから、メタンガスハイドレートの生成に必要な圧力がメタンガスハイドレートにかけられている状態にある。メタンガスハイドレートは、相平衡の状態に保たれており、また地殻温度による低温状態に保てたれいる。相平衡状態にあるメタンガスハイドレートは図１に示される温度圧力の関係を有するものである。 The part (2) in which methane gas hydrate is stored is the middle part of the seabed where methane is stored, such as the continental shelf. This part is constantly in a natural state and kept at a constant temperature. Although the temperature varies depending on the specific area, it may be considered that the temperature is generally maintained at about 278 to 288K. Details of this temperature are measured in advance. Moreover, since it exists in the ground under the seabed, it is in the state in which the pressure required for the production | generation of methane gas hydrate is applied to methane gas hydrate. Methane gas hydrate is kept in a phase equilibrium state and kept at a low temperature due to crustal temperature. The methane gas hydrate in the phase equilibrium state has the temperature-pressure relationship shown in FIG.
メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段（３）は、プラットホーム上にポンプを有し、空気の供給量（流量）を調節できるようになっており、かつ空気圧入井を有するものである。メタンガスハイドレート層に前記空気を供給する手段により空気を供給すると、メタンガスハイドレート層のメタンガスハイドレートに対して一定の圧力で浸透し、結果としてメタンガスハイドレートを分解しやすい方法に導くことができる。このようにして、メタンガスハイドレートの相平衡をずらして、メタンガスハイドレートを分解しやすい条件に導くことができる。そして、ポンプから供給される空気は輸送手段（圧入井）により、メタンガスハイドレートが蓄えられている部分に送られるようになっている。 The means (3) for supplying the required amount of air to the portion where the methane gas hydrate is stored has a pump on the platform, can adjust the air supply amount (flow rate), and is a pneumatic well. It is what has. When air is supplied by the means for supplying air to the methane gas hydrate layer, it can penetrate into the methane gas hydrate in the methane gas hydrate layer at a constant pressure, and as a result, it can lead to a method that facilitates decomposition of the methane gas hydrate. . In this way, it is possible to shift the phase equilibrium of the methane gas hydrate and lead to a condition where the methane gas hydrate is easily decomposed. And the air supplied from a pump is sent to the part by which the methane gas hydrate is stored by the transport means (press injection well).
メタンガスハイドレートが分解されて発生するメタンを回収する回収手段は、メタンガスハイドレートが蓄えられている部分に設けられている輸送手段（生産井）を介して取り出し、ポンプにより輸送取出しが行なわれ、さらにパイプ輸送或いは船上の貯蔵手段などに貯蔵されるようになっている。 The recovery means for recovering the methane generated by the decomposition of the methane gas hydrate is taken out through the transport means (production well) provided in the part where the methane gas hydrate is stored, and the transport is taken out by the pump. Further, it is stored in a pipe transportation or ship storage means.
低温高圧下にあるメタンガスハイドレートを分解してメタンガスを取り出す際には、漸近も通り、相平衡状態にあるメタンガスハイドレート中に空気を送入し、分解領域となるように維持しつつガスを放出させることによりハイドレート層の分解反応によりメタンガスを取り出す。
相平衡状態にあるメタンガスハイドレートの状態は、図１に示されている通りである。前記操作において、相平衡状態にあるメタンガスハイドレート層中に空気を送入し、メタンガスハイドレート層が分解領域となるようにメタンガスを放出させる際の空気の温度は、通常メタンガスハイドレートと同様の温度である。一般的は２７８〜２８８Ｋ程度である。圧力が一定とは、メタンガスハイドレートが保たれている圧力に対して幾分加圧する状態を指している。通常、圧力が７〜２５ＭＰａ程度の範囲である。
前記メタンガスハイドレートの分解領域となるように空気を供給することにより、メタンガスハイドレート層が分解反応をして、その結果、相平衡条件は高圧側に移行し、原位置のメタンガスハイドレート層は分解領域となり、分解されやすい側に移行し、反応が促進される。前記圧力が一定となるようにガスを放出されるが、圧力が一定とは、メタンガスハイドレートが保たれている圧力に対して幾分加圧された状態を指している。
以下、具体的な模擬実験によるメタンガスハイドレートの分解反応の態様について説明する。これは本発明の内容を支持する十分な実験内容であり、実験により得られる結果も本発明の内容を十分に確認することができるものである。
When decomposing methane gas hydrate under low temperature and high pressure and taking out methane gas, as it is asymptotically, air is fed into the methane gas hydrate in phase equilibrium, and the gas is maintained while maintaining the decomposition region. By releasing, methane gas is taken out by the decomposition reaction of the hydrate layer.
The state of the methane gas hydrate in the phase equilibrium state is as shown in FIG. In the above operation, the temperature of the air when the air is fed into the methane gas hydrate layer in a phase equilibrium state and the methane gas is released so that the methane gas hydrate layer becomes a decomposition region is usually the same as that of the methane gas hydrate. Temperature. Generally, it is about 278-288K. The constant pressure refers to a state where the pressure is somewhat increased with respect to the pressure at which the methane gas hydrate is maintained. Usually, the pressure is in the range of about 7 to 25 MPa.
By supplying air so that it becomes the decomposition region of the methane gas hydrate, the methane gas hydrate layer undergoes a decomposition reaction, and as a result, the phase equilibrium condition shifts to the high pressure side, and the in situ methane gas hydrate layer is It becomes a decomposition region and moves to the side where it is easily decomposed, and the reaction is promoted. The gas is released so that the pressure is constant. The constant pressure indicates a state where the pressure is somewhat increased with respect to the pressure at which the methane gas hydrate is maintained.
Hereinafter, the aspect of the decomposition reaction of methane gas hydrate by a specific simulation experiment will be described. This is sufficient experimental content to support the content of the present invention, and the results obtained by the experiment can sufficiently confirm the content of the present invention.
メタンガスハイドレートの分解挙動について，図3に示されている実験装置により行なった。図３の装置は、実際にメタンガスハイドレートを分解して取り出す場所及びその装置である図２の海底下を模擬したものである。
実験装置は高圧容器部，恒温装置部，ガス制御部，データ計測部から成っている。高圧容器本体は内径20cm，高さ40cm，内容積12l，最高使用圧力30MPaのステンレス製である。本体は温度を制御するため全体を恒温槽に浸している。高圧容器は上下にステンレス製カバーをボルトで締め付けており，上カバーにはガス排出口を，下カバーにはガス入口を設けている。温度センサは容器側面から引き込み、容器中心部の高さ方向に16点、容器底面から10cmと20cmの位置に横方向に各10点を配置している。
メタンおよび空気はボンベより増圧器、流量計，圧力センサおよび高圧バルブを経て高圧容器に圧入する。ガス排出経路には圧力センサ，高圧バルブ、流量計およびガスサンプル口を設けている。高圧容器内部の圧力，温度およびガス経路における流量の各データは各センサで計測し，パーソナルコンピュータに収録する。
実験の手順は次の通りである。まず、高圧容器に堆積層を模擬する豊浦標準砂と純水を細密充てんし，自由水を抜いてから容器内の温度を7℃付近まで低下させる。次に、メタンガスを所定の圧力まで圧入し，メタンハイドレートを生成・成長させる。次に、空気を圧入し、容器内部の圧力が一定になるように一定流量で放出する。そのとき、メタンハイドレートが分解する。放出ガスを連続でガス分析し、分解量を求める。分解が終わった後、高圧容器内に存在するガスを大気圧まで放出し，その間、ガス分析とガス量を計測する。実験の期間中，ガスの入・排出経路に設置した圧力センサで圧力変化を，高圧容器内に設置した温度センサで容器内部の温度変化を測定する。
空気によるメタンガスハイドレート分解時の温度変化を図4に示す。空気を一定量流し、圧力を一定になるようにガスを放出し、そのガスを高速ガスクロで分析した。図から、空気を圧入するとほぼ同時に容器下部からメタンガスハイドレートの分解による吸熱反応で温度の低下が見られた。温度変化は最大で約6.5℃からマイナス温度まで低下した。容器下部から約79ｍｍまではメタンガスハイドレートの成長が弱いため、短時間で反応は終了し、恒温槽温度に依存して上昇した。メタンガスハイドレートの成長が強い位置ではマイナス温度まで低下した。
圧入した空気と放出ガス量の差は反応初期で空気の約2倍の放出量であり、時間とともに放出ガス量は減少し、反応の終わりではほぼ同じ量を示した。
交換反応時のガス組成変化を図5に示す。空気を圧入しながら容器内の圧力を一定となるようにガスを放出し、そのガスを5分間隔で分析した。放出初期では容器内部のガス相を満たしていたメタンガスがほぼ100％を示し、その後、空気と分解したメタンが混合ガスとなり、メタンは徐々に低下し、空気（窒素と酸素）は逆に上昇した。空気がほぼ100％になった時点で反応の終了とした。
ガス分析とガス量計測から、使用したメタンガスの総量は約703lで、その内、ハイドレート化したガス量は約417lであった。交換反応に用いた空気の量は約2155lである。これらのことから、メタンハイドレートの空気による分解ガス量は0.45l/minであることが分かった。また、反応時間765minでメタンハイドレートの82％を分解することを明らかにした。
The decomposition behavior of methane gas hydrate was measured using the experimental apparatus shown in Fig. 3. The apparatus of FIG. 3 simulates the place where the methane gas hydrate is actually decomposed and taken out, and the subsea floor of FIG. 2 which is the apparatus.
The experimental equipment consists of a high-pressure vessel, a constant temperature device, a gas control unit, and a data measurement unit. The body of the high-pressure vessel is made of stainless steel with an inner diameter of 20 cm, a height of 40 cm, an internal volume of 12 l, and a maximum working pressure of 30 MPa. The main body is immersed in a constant temperature bath to control the temperature. The high-pressure vessel has a stainless steel cover bolted up and down, a gas exhaust port in the upper cover, and a gas inlet in the lower cover. The temperature sensor is drawn from the side of the container, and 16 points are arranged in the height direction at the center of the container, and 10 points in the lateral direction at 10 cm and 20 cm positions from the bottom of the container.
Methane and air are press-fitted from a cylinder into a high-pressure vessel via a pressure intensifier, flow meter, pressure sensor, and high-pressure valve. The gas discharge path is provided with a pressure sensor, a high pressure valve, a flow meter, and a gas sample port. The pressure, temperature, and gas flow data inside the high-pressure vessel are measured by each sensor and recorded in a personal computer.
The experimental procedure is as follows. First, a high-pressure vessel is packed with Toyoura standard sand that simulates a sedimentary layer and pure water. After free water is drained, the temperature inside the vessel is lowered to around 7 ℃. Next, methane gas is injected to a predetermined pressure to generate and grow methane hydrate. Next, air is injected and discharged at a constant flow rate so that the pressure inside the container becomes constant. At that time, methane hydrate decomposes. Analyze the released gas continuously to determine the amount of decomposition. After decomposition, the gas present in the high-pressure vessel is released to atmospheric pressure, and during that time, gas analysis and gas volume are measured. During the experiment, the pressure change is measured with the pressure sensor installed in the gas inlet / outlet route, and the temperature change inside the container is measured with the temperature sensor installed in the high-pressure vessel.
Fig. 4 shows the temperature change during methane gas hydrate decomposition by air. A constant amount of air was flowed to release the gas so that the pressure was constant, and the gas was analyzed by high-speed gas chromatography. From the figure, when air was injected, the temperature decreased due to the endothermic reaction caused by the decomposition of methane gas hydrate from the bottom of the container almost simultaneously. The temperature change decreased from a maximum of about 6.5 ° C to minus temperature. Since the growth of methane gas hydrate was weak from the bottom of the vessel to about 79 mm, the reaction was completed in a short time and increased depending on the temperature of the thermostatic chamber. In the position where methane gas hydrate growth was strong, it decreased to minus temperature.
The difference between the injected air and the amount of released gas was about twice the amount of air at the beginning of the reaction, the amount of released gas decreased with time, and was almost the same at the end of the reaction.
The change in gas composition during the exchange reaction is shown in FIG. While injecting air, gas was released so that the pressure in the container was constant, and the gas was analyzed at intervals of 5 minutes. The methane gas that filled the gas phase inside the container showed almost 100% at the beginning of the release, and then the air and decomposed methane became a mixed gas, the methane gradually decreased, and the air (nitrogen and oxygen) rose on the contrary . The reaction was terminated when the air was almost 100%.
From the gas analysis and gas amount measurement, the total amount of methane gas used was about 703 l, of which the amount of hydrated gas was about 417 l. The amount of air used for the exchange reaction is about 2155 l. From these results, it was found that the amount of methane hydrate cracked by air was 0.45 l / min. It was also revealed that 82% of methane hydrate was decomposed in a reaction time of 765 min.
１ メタンガスハイドレートを分解してメタンガスを取り出す全体装置
２ メタンガスハイドレートが蓄えられている部分、
３ メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段
４ メタンガスハイドレートが分解されて発生するメタンを回収する回収手段
５ メタンガスハイドレートが蓄えられている部分に必要量の空気を供給する手段及びメタンガスハイドレートが分解されて発生するメタンを回収する回収手段が設けられているプラットホーム
1 Whole device for decomposing methane gas hydrate and taking out methane gas 2 Part where methane gas hydrate is stored,
3 Means for supplying a required amount of air to the portion where methane gas hydrate is stored 4 Recovery means for recovering methane generated by decomposition of methane gas hydrate 5 Required amount of air for the portion where methane gas hydrate is stored And a recovery means for recovering methane generated by decomposition of methane gas hydrate
Claims (5)
The means for supplying the necessary amount of air to the portion where the methane gas hydrate is stored is a means for monitoring the decomposition process by means of a temperature sensor provided in the portion where the methane gas hydrate is stored, and methane gas hydrate 5. The methane gas hydrate decomposed at low temperature and high pressure by decomposing methane gas hydrate, comprising an air amount supply means capable of calculating an amount of air necessary for maintaining the stored portion at a constant pressure. Device to take out.
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