JP4711989B2 - Carbon dioxide coal seam fixing method - Google Patents
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Description
この発明は、地下の石炭層に二酸化炭素を圧入し石炭に吸着させて固定する二酸化炭素の炭層固定方法に関し、さらに石炭から遊離の炭化水素系ガスを地中から回収可能である二酸化炭素の炭層固定方法に関する。 TECHNICAL FIELD The present invention relates to a carbon dioxide coal seam fixing method in which carbon dioxide is injected into an underground coal seam and adsorbed to the coal to fix it, and further, a carbon dioxide coal seam capable of recovering hydrocarbon-based gas free from coal from the ground. It relates to the fixing method.
一般に、石炭は、細孔構造が発達しているため、細孔(ミクロポア：大きさ２０Å以下)にファンデル・ワールス(Van der Waals)力によって気体が吸着する作用がある。このような石炭を含有する炭層には、メタンガスを主成分とする炭化水素系ガスが遊離ガスよりも遥かに多量に吸着されていることが知られている。 Generally, since the pore structure of coal is developed, there is an effect that gas is adsorbed by the van der Waals force in the pores (micropores: size of 20 mm or less). It is known that a hydrocarbon-based gas mainly composed of methane gas is adsorbed in such a coal bed containing coal in a much larger amount than free gas.
ところで、地球温暖化現象の原因である温室効果ガスの一つとして知られる二酸化炭素は、石炭に対してメタンの数倍量も吸着される物性であるため、これを採掘困難な深部炭層や経済性の低い炭層に圧入すれば、石炭中に吸着されているメタンガス等の炭化水素系ガスが置換されて遊離するから、有用なガスエネルギー資源が回収可能になる。 By the way, carbon dioxide, which is known as one of the greenhouse gases that cause the global warming phenomenon, is a physical property that adsorbs several times the amount of methane to coal. If it is injected into a coal layer with low properties, hydrocarbon gas such as methane gas adsorbed in the coal is replaced and released, so that useful gas energy resources can be recovered.
すなわち、二酸化炭素を安定した石炭層中に隔離して固定し、しかも二酸化炭素と置換されて生産されるメタンガス等を回収してクリーンエネルギーとして利用すると、経済的にも地球環境上も有用な資源循環とその利用が可能である。 In other words, if carbon dioxide is isolated and fixed in a stable coal bed, and methane gas etc. produced by replacing carbon dioxide is recovered and used as clean energy, it is an economically useful resource for the global environment. Circulation and its use are possible.
具体的に説明すると、石炭層に通じる孔井から地下の石炭層に二酸化炭素を圧入すると、石炭にはメタンの２倍から数倍量の二酸化炭素が選択的に吸着され、その代わりに石炭に吸着されていたメタンガスを主成分とする炭化水素系ガスが遊離し放出される。 Specifically, when carbon dioxide is injected into the underground coal seam from the borehole leading to the coal seam, the carbon dioxide is selectively adsorbed to the coal twice to several times as much as methane. The hydrocarbon-based gas mainly composed of adsorbed methane gas is released and released.
このように二酸化炭素−メタンの置換を利用して、石炭層中に多量に含まれるメタンガスを燃料ガスとして別の孔井から回収して利用できることが知られている。（例えば特許文献１） As described above, it is known that methane gas contained in a large amount in a coal bed can be recovered and used as a fuel gas from another borehole by using carbon dioxide-methane substitution. (For example, Patent Document 1)
しかし、上記のように二酸化炭素を地中に圧入するとき、二酸化炭素が石炭層の内部に深く浸透するために必要な通路となる「クリート」と称される微小割れ目状の隙間を必要とするが、二酸化炭素を吸収した石炭組織は膨潤するので、その膨潤によって通路となるクリートの空隙が狭まり、二酸化炭素の圧入抵抗が増し、二酸化炭素の炭層への浸透率が低下して二酸化炭素と置換されるメタンガス等の可燃性ガスの回収率も低下するという問題点がある。 However, when carbon dioxide is injected into the ground as described above, a minute crack-like gap called “cleat” that becomes a passage necessary for the carbon dioxide to penetrate deeply into the coal bed is required. However, since the coal structure that has absorbed carbon dioxide swells, the swelling of the cleats that become the passage narrows, and the press-fitting resistance of carbon dioxide increases, and the permeability of carbon dioxide to the coal bed decreases to replace carbon dioxide. There is a problem that the recovery rate of combustible gas such as methane gas is also lowered.
実際の石炭層において本願の発明者らの推定によれば、石炭組織が膨潤することによるガス浸透性の影響は、特に石炭層に対する二酸化炭素の圧入部周辺で最も大きいと考えられ、二酸化炭素の石炭層内通路のかなり上流部分で大部分の二酸化炭素の圧入量が規制されているものと考えられる。 According to the estimation of the inventors of the present application in an actual coal bed, the influence of gas permeability due to the swelling of the coal structure is considered to be the largest especially in the vicinity of the injecting portion of carbon dioxide to the coal bed. It is thought that most carbon dioxide injection is regulated in the upstream part of the passage in the coal seam.
そこで、この発明の課題は、上記した問題点を解決して、石炭層に圧入される二酸化炭素による炭層の要所における膨潤状態を抑制し、これにより二酸化炭素の浸透性のよい状態を経時的に安定的に確保し、または二酸化炭素の圧入可能量を必要に応じて速やかに改善させ、効率よく二酸化炭素の炭層固定を行なうことができるようにすることである。 Therefore, an object of the present invention is to solve the above-described problems and suppress the swelling state at the key points of the coal seam due to carbon dioxide injected into the coal seam, thereby improving the state of good carbon dioxide permeability over time. In other words, the amount of carbon dioxide that can be press-fitted is improved as needed, and carbon dioxide coal bed fixation can be performed efficiently.
また、二酸化炭素の炭層固定による副次的な効果が得られるように、炭層に固定される二酸化炭素と置換されて遊離した炭化水素系ガスを地中から効率よく回収可能とする二酸化炭素の炭層固定方法とすることである。 In addition, carbon dioxide coal bed that can efficiently recover hydrocarbon-based gas that has been replaced by carbon dioxide fixed to the coal bed and released from the ground so that the secondary effect of carbon dioxide coal bed fixation can be obtained. The fixing method.
上記の課題を解決するために、この発明においては、地中の石炭層に通じる孔井に二酸化炭素を圧入して石炭層に浸透させかつ吸着させる二酸化炭素の炭層固定方法において、
前記石炭層に二酸化炭素を圧入することにより膨潤した石炭層に対し、石炭に対する浸透率が二酸化炭素より高い物質からなる高浸透性ガスを二酸化炭素に代えて圧入し、この圧入により二酸化炭素浸透率の改善された石炭層に対して再び二酸化炭素を圧入することを特徴とする二酸化炭素の炭層固定方法としたのである。
In order to solve the above-mentioned problem, in the present invention, in the coal bed fixing method of carbon dioxide for injecting and adsorbing carbon dioxide into the borehole leading to the underground coal bed,
For the coal bed swollen by injecting carbon dioxide into the coal bed, a high permeability gas made of a substance having a higher permeability to the coal than carbon dioxide is injected instead of carbon dioxide, and the carbon dioxide penetration rate is obtained by this injection. The carbon dioxide coal seam fixing method is characterized in that carbon dioxide is again injected into the improved coal seam.
上記したように構成されるこの発明の二酸化炭素の石炭層固定方法は、二酸化炭素に代えて圧入する高浸透性ガスの石炭に対する浸透率が二酸化炭素より高いという特性により、石炭層中の二酸化炭素ガスの分圧を下げることができると共に、二酸化炭素ガスの分圧低下によって石炭の膨潤を停止させ、さらには膨潤した状態から収縮させるようにできるので、膨潤状態で狭窄された通路は広げられて、膨潤状態より低い圧力で効率よく二酸化炭素を石炭層に圧入し浸透させられるようになり、二酸化炭素の固定処理効率およびそれに伴う炭化水素系ガスの回収率が高まる。 The carbon dioxide coal bed fixing method of the present invention configured as described above is characterized in that the permeability of the highly permeable gas injected instead of carbon dioxide to coal is higher than that of carbon dioxide. The gas partial pressure can be lowered and the swelling of coal can be stopped by shrinking the partial pressure of carbon dioxide gas, and further the contraction can be made to shrink from the swollen state, so that the passage narrowed in the swollen state is expanded. Thus, carbon dioxide can be efficiently injected into the coal bed at a pressure lower than that in the swollen state, and the carbon dioxide fixation treatment efficiency and the hydrocarbon gas recovery rate associated therewith can be increased.
石炭層に対する二酸化炭素の圧入工程と、高浸透性ガスの圧入工程を交互に繰り返し、石炭層に対して二酸化炭素を間欠的に吸着させることにより、石炭組織の細孔が速やかに間欠的に開かれた状態になって石炭層の浸透率が効率よく高められ、長期間に亘って石炭層を二酸化炭素の固定処理に効率よく利用できる。上記の高浸透性ガスの圧入が、圧入と停止を繰り返す間欠的な圧入である方法を採用すれば、さらに効率よく二酸化炭素を炭層に固定することができる。 By alternately repeating the process of injecting carbon dioxide into the coal bed and the process of injecting highly permeable gas, and intermittently adsorbing carbon dioxide into the coal bed, the pores of the coal structure are rapidly and intermittently opened. In this state, the permeability of the coal bed is efficiently increased, and the coal bed can be efficiently used for the carbon dioxide fixation treatment over a long period of time. By adopting a method in which the above-mentioned high-osmotic gas injection is intermittent injection that repeats injection and stop, carbon dioxide can be more efficiently fixed to the coal bed.
上記した高浸透性ガスとしては、石炭に対する浸透率が二酸化炭素よりも高い物質であればよく、すなわち石炭に対する吸着性が二酸化炭素より低い物質からなる高浸透性ガスである窒素やヘリウムなどをその１００体積％中に４．０〜８７体積％を占める高浸透性ガスであるものを使用すれば、上記したような作用が確実に得られる。 As the above-described highly permeable gas, any material having a higher permeability to coal than carbon dioxide may be used, that is, nitrogen, helium, or the like, which is a highly permeable gas made of a material having a lower adsorptivity to coal than carbon dioxide. The use of what is a highly permeable gas occupying 4.0 to 87% by volume in 100% by volume will surely provide the above-described action.
また、石炭組織内部のクリートの空隙が広がることにより、高浸透性ガスの圧入以前よりも低い圧力で効率よく二酸化炭素を石炭層に圧入・浸透できるようになり、吸着した二酸化炭素に置換されて石炭から遊離した炭化水素系ガスを別途設けた孔井から回収することが、安定して効率よく実行できるようになり、経済的にも優れた炭化水素系ガスの生産が可能となる。 In addition, because the cleat voids inside the coal structure are expanded, carbon dioxide can be efficiently injected and penetrated into the coal bed at a lower pressure than before the injection of the highly permeable gas. Recovery of the hydrocarbon-based gas liberated from coal from a well provided separately can be performed stably and efficiently, and it is possible to produce a hydrocarbon-based gas that is economically superior.
この発明は、石炭層に二酸化炭素を圧入することにより膨潤した石炭層に対し、石炭に対する浸透性が二酸化炭素より高い物質からなる高浸透性ガスを二酸化炭素に代えて圧入することにより、浸透率の改善された石炭層に対して二酸化炭素を圧入できるので、石炭層に対する二酸化炭素の浸透性が速やかに高まり、再び低い圧力での二酸化炭素の圧入が可能になって、効率よく二酸化炭素の炭層固定を行なうことができる利点がある。 The present invention relates to a coal bed swollen by injecting carbon dioxide into the coal bed, and instead of injecting carbon dioxide with a highly permeable gas made of a material having a higher permeability to carbon than carbon dioxide, the permeability is increased. Because carbon dioxide can be injected into the improved coal bed, the carbon dioxide permeability into the coal bed is increased quickly, and carbon dioxide can be injected again at a low pressure. There is an advantage that fixing can be performed.
また、二酸化炭素の炭層固定による副次的な効果として、炭層に固定される二酸化炭素と置換されて遊離した炭化水素系ガスを地中から効率よく回収できるという利点もある。 Further, as a secondary effect of fixing the carbon dioxide in the coal seam, there is an advantage that the hydrocarbon-based gas which has been replaced with carbon dioxide fixed in the coal seam and released can be efficiently recovered from the ground.
この発明の実施形態を以下に、添付図面に基づいて説明する。
図１に示すように、実施形態は、地中に存在する本層１と下層２からなる石炭層に下層２に通じる圧入井３および生産井４からなる２本の孔井を設け、これらの孔井のうち圧入井３の二酸化炭素注入管８から二酸化炭素を圧入して下層２内の石炭に固定させ、その後、二酸化炭素と置換されて放出されるメタンガスを主成分とする炭化水素系ガスを生産井４から回収する。この二酸化炭素固定および炭化水素系ガスの生産システムにおいて適用される二酸化炭素の炭層固定方法である。
Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIG. 1, in the embodiment, a coal bed composed of a
このような生産システムにおいて、圧入井３は、図２に示される構造からなり、例えば液化炭酸を用いる場合は、図１に示される液化炭酸貯槽５から昇圧ポンプ６を介して配管内を圧送して蒸発器７で加熱し、気化させてから制御弁１１および流量計１２を経由して圧入井３から炭層に導入する。なお、図２中の符号１５は、圧力等のセンサーおよび圧力媒体の挿入口である。
In such a production system, the
この発明に用いる二酸化炭素は、火力発電所等の大規模発生源からの二酸化炭素を含む排気ガスを分離回収したものを用いることができる。なお、実験に用いることのできる高純度の二酸化炭素は、モノエタノールアミンなどのアミン吸収剤に吸収させて回収するアミン法により比較的簡単に得ることができる。 As the carbon dioxide used in the present invention, one obtained by separating and recovering exhaust gas containing carbon dioxide from a large-scale generation source such as a thermal power plant can be used. Note that high-purity carbon dioxide that can be used in experiments can be obtained relatively easily by the amine method in which it is absorbed and recovered by an amine absorbent such as monoethanolamine.
二酸化炭素の圧入は、図示したような一箇所の圧入井３から行なうばかりでなく、複数の圧入井から行なってもよい。また、圧入の初期には、比較的高い圧力で行なうことにより、石炭層を破壊して多数の割れ目（クラック）を積極的に形成させて圧入することが好ましく、また、必要に応じて砂などを混入させて割れ目の閉塞を防止することも好ましい。 The injection of carbon dioxide may be performed not only from one injection well 3 as shown, but also from a plurality of injection wells. In addition, at the initial stage of the press-fitting, it is preferable to press-fit by forming a large number of cracks (cracks) by destroying the coal layer by performing at a relatively high pressure. It is also preferable to prevent the clogging of the cracks by mixing.
窒素などの高浸透性ガスは、例えば窒素ガスボンベ（例えば圧力１５ＭＰａのボンベを２０本程度組み合わせたもの）を連結したカードル１４から供することができ、減圧弁１３を介して前記の流量計１２を経由して圧入井３から炭層に導入する。また、このような窒素ガスボンベを用いた例ばかりでなく、液体窒素を用いて気化させ、さらに加圧調整した窒素ガスを用いることなどもできるのは勿論である。
また、このような窒素ガスの圧入時の圧力（炭層クリートの間隙圧力）は、１５．８ＭＰａ以下の程度に設定される場合が通例である。
Highly permeable gas such as nitrogen can be provided from a
Further, the pressure at the time of such nitrogen gas press-fitting (gap pressure of the coal seam cleat) is usually set to about 15.8 MPa or less.
生産井４は、圧入井から炭層に浸透した二酸化炭素が充分吸着されるのに必要な距離を離して設置することが好ましい。このような距離は、少なくとも数十メートル必要であるものと考えられる。
なお、生産井４は、圧入井３から立体的な位置関係によって上記の所定距離だけ離れていればよく、必ずしも平面的な方向に離間させておく必要はなく、例えば、炭層の深部に二酸化炭素を圧入して同一領域の浅部からメタンガスを含む地中ガスを回収してもよく、深部から浅部まで傾斜して平面的に延びる炭層である場合には、深部で二酸化炭素を圧入して浅部から生産するようにしてもよい。
The
Note that the production well 4 only needs to be separated from the injection well 3 by the above-described predetermined distance depending on the three-dimensional positional relationship, and is not necessarily separated in a planar direction. The underground gas containing methane gas may be recovered from the shallow part of the same region by injecting carbon dioxide, and in the case of a coal bed extending in a plane inclined from the deep part to the shallow part, carbon dioxide is injected in the deep part. You may make it produce from a shallow part.
通常、生産井４から回収された水蒸気などを含む地中ガスは、気液分離装置１０で液体を分離し、液体成分をタンク９ａ、９ｂに回収すると共に、分離したメタンガスを主成分とする炭化水素系ガスを得る。必要に応じて、さらにガスを精製してもよく、その後これを利用する施設に配送する。
Normally, underground gas including water vapor and the like recovered from the production well 4 is separated into liquid by the gas-
この発明で用いる石炭に対する浸透性が二酸化炭素より高い物質からなる高浸透性ガスは、予め石炭に吸着されている二酸化炭素より、通気抵抗の少ない高浸透性ガスを採用することができ、すなわち二酸化炭素に比べて石炭に対する親和性、すなわち吸着性が低い元素のガスを採用することができる。 As the highly permeable gas composed of a material having higher permeability than carbon dioxide used in the present invention, a highly permeable gas having a lower airflow resistance than carbon dioxide previously adsorbed on coal can be adopted. It is possible to employ an elemental gas having a lower affinity for coal than carbon, that is, an adsorptivity.
また、地中への圧入作業に伴う安全性、すなわち、引火性や爆発性の低いガスを採用することが実用的であるために、そのような高浸透性ガスの代表例としては、窒素ガスまたはヘリウムガスが挙げられる。因みに、石炭に対する吸着性は、二酸化炭素がメタンの約２倍であり、窒素はメタンの半分であるといわれており、ヘリウムガスは、石炭には殆ど吸着しないと考えられる。 In addition, since it is practical to employ the safety associated with the press-fitting work into the ground, that is, a gas with low flammability and explosiveness, a typical example of such a highly permeable gas is nitrogen gas. Or helium gas is mentioned. Incidentally, the adsorptivity to coal is said to be about twice that of methane for carbon dioxide and half that of methane for nitrogen, and helium gas is considered to hardly adsorb to coal.
炭層に対する二酸化炭素の圧入と、高浸透性ガスの圧入を交互に繰り返す場合、その時間配分は、例えば高浸透性ガスの圧入を４〜１５時間程度の範囲において適宜に調整すればよく、二酸化炭素の圧入量の改善の程度が顕著に低下したときに、高浸透性ガスの圧入を開始すればよく、特に限定されるものではない。
しかしながら、高浸透性ガスの圧入の直後の１〜４時間程度において顕著に二酸化炭素の圧入量が改善され、その後の５〜６時間の安定状態を経て急に低下することから、１０〜１２時間ごとに数時間（４〜５時間）の高浸透性ガスの圧入を行なうことが好ましい。
In the case where the injection of carbon dioxide into the coal bed and the injection of the highly permeable gas are repeated alternately, the time distribution may be appropriately adjusted, for example, in the range of about 4 to 15 hours for the injection of the highly permeable gas. When the degree of improvement of the press-in amount is significantly reduced, the press-in of the highly permeable gas may be started and is not particularly limited.
However, in about 1 to 4 hours immediately after the injection of the highly permeable gas, the amount of carbon dioxide injection is remarkably improved, and then rapidly decreases after a stable state of 5 to 6 hours. It is preferable to press-in the highly permeable gas every several hours (4 to 5 hours).
そして、上記の高浸透性ガスの圧入が、圧入と停止を繰り返す間欠的な圧入である方法を採用すれば、圧入された高浸透性ガスの炭層内での拡散と反応が、無駄なく効率よく進行するものと考えられ、実際にその後に効率よく二酸化炭素を炭層に固定することができる。 Then, if the above-described method of injecting the highly permeable gas is intermittent injection that repeats the injecting and stopping, the diffusion and reaction of the injected highly permeable gas in the coal bed can be efficiently performed without waste. It is considered to proceed, and in fact, carbon dioxide can be efficiently fixed to the coal bed thereafter.
図１に示した石炭層を有する北海道南大夕張地区の地層構造において、長期間のフィールド試験を行なった。
そして、圧入井３から、表１に示す窒素および二酸化炭素の圧入条件（注入時間（ｈ）、注入量（ｋｇ））で略一定圧力８．０〜１３．５ＭＰａでの圧入処理を約１週間にわたって交互に間欠的に行ない、このときに用いた窒素ガス量と圧入できた二酸化炭素量のデータを表１および図３の図表に示した。
A long-term field test was conducted on the geological structure of Hokkaido Minami-Dayubari area with the coal layer shown in FIG.
Then, from the injection well 3, a press-in process at a substantially constant pressure of 8.0 to 13.5 MPa is performed for about one week under the nitrogen and carbon dioxide injection conditions (injection time (h) and injection amount (kg)) shown in Table 1. The data of the amount of nitrogen gas used at this time and the amount of carbon dioxide that could be injected were shown in Tables 1 and 3.
これらの結果からも明らかなように、二酸化炭素の炭層への浸透率が低下した時、４〜１５時間の窒素ガス圧入を行なうことにより、次に二酸化炭素の圧入を低い圧入抵抗で行なうことができ、二酸化炭素を再び効率よく炭層に浸透できるようになったことがわかる。
そして、圧入する二酸化炭素量に比べて少量の窒素ガス量で浸透率が充分に改善できていることから、常に二酸化炭素と窒素ガスの混合ガスを使用する場合よりも、間欠的に窒素ガスを圧入する方が窒素ガスの浸透率改善の作用効率が高く、それだけメタンガスなどの炭化水素系ガスの生産に窒素ガスの混合される割合は低くなるものと考えられる。
As is clear from these results, when the carbon dioxide penetration rate into the coal bed decreases, nitrogen gas can be injected for 4 to 15 hours, so that carbon dioxide can be injected with a low resistance. It can be seen that carbon dioxide can efficiently penetrate into the coal seam again.
And since the permeability can be improved sufficiently with a small amount of nitrogen gas compared to the amount of carbon dioxide to be injected, nitrogen gas is intermittently used rather than when a mixed gas of carbon dioxide and nitrogen gas is always used. It is considered that the pressure injection improves the efficiency of nitrogen gas permeation improvement, and the proportion of nitrogen gas mixed into the production of hydrocarbon gas such as methane gas is considered to be lower.
図４の結果からも明らかなように、窒素ガスの圧入が、圧入と停止を繰り返す間欠的な圧入である方法を採用すると、１回目の窒素ガスの圧入量に比べて同じ圧力で２回目の窒素ガス圧入量の方が格段に増加しており、その後の二酸化炭素ガスの圧入量も顕著に増加していることがわかる。 As is clear from the results of FIG. 4, when the method in which the nitrogen gas press-fitting is intermittent press-fitting that repeats the press-fitting and the stop is adopted, the second pressurization is performed at the same pressure compared to the first nitrogen gas press-fitting amount. It can be seen that the nitrogen gas injection amount has increased remarkably, and the subsequent carbon dioxide gas injection amount has also increased significantly.
また、二酸化炭素を吸着した石炭に窒素を注入した場合に、その浸透率が改善されるかどうかを確認するために、以下の室内実験を行なった。
すなわち、夕張炭層下層の石炭資料を採取し、篩にかけて粒径２５０〜５００μｍの石炭粒子約６０ｇをゴムチューブに詰め、ゴムチューブ両端には焼結金属製のエンドピースを挿入したものをコールパック資料とした。
Moreover, in order to confirm whether the penetration rate is improved when nitrogen is injected into coal adsorbed with carbon dioxide, the following laboratory experiment was conducted.
In other words, the coal material under the Yubari coal layer is collected, passed through a sieve, packed with about 60 g of coal particles with a particle size of 250-500 μm in a rubber tube, and sintered metal end pieces inserted at both ends of the rubber tube. It was.
実験装置は、コールパック試料を装着する圧力容器と封圧を制御するシリンジポンプ、浸透圧を計測するための差圧変換器、流量計、コールパック資料内の間隙圧を調整する背圧弁、データを収集するためのパーソナルコンピュータなどからなる。圧力容器およびコールパックへのガス注入量及び吸着量を計測するためのバッファタンクは、水槽に入れ温度制御した。 The experimental equipment consists of a pressure vessel to which the call pack sample is attached, a syringe pump that controls the sealing pressure, a differential pressure transducer for measuring osmotic pressure, a flow meter, a back pressure valve that adjusts the pore pressure in the call pack material, data It consists of a personal computer etc. for collecting. A buffer tank for measuring the amount of gas injected into the pressure vessel and the coal pack and the amount of adsorption was placed in a water tank and the temperature was controlled.
実験手順は、先ずコールパック試料を作製し、圧力容器内にセットし、次に石炭試料に吸着しているガスを除くために40℃で24時間真空ポンプで吸引した。そして、封圧と間隙圧を設定圧力にセットし、一定時間毎に浸透圧を測定した。封圧は間隙圧よりも約1ａｔｍ高い圧力で設定し間隙流体の漏れを防止した。そして、間隙圧が10ａｔｍになるようにＣＯ2を注入し、平衡圧での浸透率を測定した。次に、ＣＯ2と同様に間隙圧が10ａｔｍになるようにＮ2を注入し、平衡圧での浸透圧を測定した。Ｎ2を注入時には浸透率測定前にコールパック内のガスを採取し、間隙内のガス組成をガスクロマトグラフィーにより分析した。 In the experimental procedure, a coal pack sample was first prepared, set in a pressure vessel, and then sucked with a vacuum pump at 40 ° C. for 24 hours in order to remove the gas adsorbed on the coal sample. Then, the sealing pressure and the gap pressure were set to the set pressure, and the osmotic pressure was measured at regular intervals. The sealing pressure was set at about 1 atm higher than the gap pressure to prevent leakage of the gap fluid. Then, CO 2 was injected so that the pore pressure was 10 atm, and the permeability at the equilibrium pressure was measured. Next, N 2 was injected so that the pore pressure was 10 atm as in the case of CO 2 and the osmotic pressure at the equilibrium pressure was measured. When N 2 was injected, the gas in the coal pack was collected before the permeability measurement, and the gas composition in the gap was analyzed by gas chromatography.
この実験結果として、図５に二酸化炭素と窒素による浸透率測定結果を示した。
その結果からも明らかなように、ＣＯ2注入は間隙圧ができる限り平衡になるように１２〜１３ａｔｍで注入され、平衡圧で浸透率の測定を行なったが、Ｎ2を注入後、平衡圧がＣＯ2の脱着により上昇しているにもかかわらず、浸透率の上昇が見られ、Ｎ2を注入後約６時間で浸透率が急激に増大したが、その後は比較的穏やかな増加傾向を示した。
As the experimental results, FIG. 5 shows the results of measuring the permeability with carbon dioxide and nitrogen.
Its As apparent from the result, CO 2 injected is injected at 12~13atm to be balanced as possible pore pressure, but was measured in the penetration rate at the equilibrium pressure, after injection of N 2, the equilibrium pressure Despite the increase in CO 2 desorption, the permeability increased, and the permeability increased rapidly about 6 hours after N 2 injection. Indicated.
図６には各ガスの間隙圧と浸透率の関係を示したが、Ｈｅによる浸透率は間隙圧の上昇と共に浸透率が減少した。ＣＯ2吸着時の間隙圧が１０ａｔｍで浸透率が多少大きくなっているが、全体的に見ると間隙圧の上昇と共に浸透率の低下傾向が見られた。間隙圧が１０ａｔｍ付近での浸透率を比較すると、ＣＯ2が吸着した試料の浸透率が最も低く、Ｎ2を注入した場合に浸透率の改善が見られた。 FIG. 6 shows the relationship between the pore pressure and the permeability of each gas, and the permeability by He decreased with the increase of the pore pressure. The permeability increased slightly when the pore pressure during CO 2 adsorption was 10 atm. However, as a whole, there was a tendency for the permeability to decrease as the gap pressure increased. When comparing the permeability when the pore pressure is around 10 atm, the permeability of the sample to which CO 2 was adsorbed was the lowest, and the improvement of the permeability was observed when N 2 was injected.
これらの実験結果から、ＣＯ2の圧入後の石炭（コールパック）に対し、Ｎ2ガスを圧入することにより、石炭層の浸透率は改善されることがわかる。また、Ｈｅガスを用いてもＮ2ガスと同様以上に石炭層の浸透率の改善を図り得ることがわかる。 From these experimental results, it is understood that the penetration rate of the coal bed is improved by injecting N 2 gas into the coal (coal pack) after CO 2 injection. It can also be seen that even if He gas is used, the coal layer penetration rate can be improved more than N 2 gas.
１ 本層
２ 下層
３ 圧入井
４ 生産井
５ 液化炭酸貯槽
６ 昇圧ポンプ
７ 蒸発器
８ 二酸化炭素注入管
９ａ、９ｂ タンク
１０ 気液分離装置
DESCRIPTION OF
Claims (5)
前記石炭層に二酸化炭素含有ガスを圧入することにより膨潤した石炭層に対し、石炭に対する浸透率が二酸化炭素より高い高浸透性ガスを圧入し、この圧入により二酸化炭素浸透率の改善された石炭層に対して再び二酸化炭素含有ガスを圧入することを特徴とする二酸化炭素の炭層固定方法。 In the method for fixing a carbon dioxide coal seam in which a carbon dioxide-containing gas is injected into a borehole leading to the underground coal seam to penetrate and adsorb to the coal seam,
The coal layer swollen by injecting a carbon dioxide-containing gas into the coal layer is injected with a highly permeable gas whose permeability to coal is higher than that of carbon dioxide, and the coal layer has improved carbon dioxide permeability by this injection. A carbon dioxide coal bed fixing method, wherein the carbon dioxide-containing gas is again injected into the carbon dioxide.
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