台灣的油氣特性與其生油源岩

Hydrocarbon Characteristics and Source Rocks in Taiwan

沈俊卿(Jun-Chin Shen)

天然氣 ； 陸源有機物 ； 含煤三角洲 ； Natural Gas ； Terrestrial Organic Matter ； Coal-Bearing Delta

石油季刊

54卷2期（2018 / 06 / 01）

1 - 15

繁體中文

臺灣周邊地區探得的油氣藏幾乎全為天然氣，僅有少量凝結油伴隨產出。發現的數量就地理分佈而言以台灣西北部最多，高達五百多億立方公尺，其次為台南盆地，南部則僅有少量發現。若從天然氣的種類來看，產自被歸為第三類型的陸源有機物（高等植物）之熱成熟氣佔絕大多數，另外則為生物氣，在南部也已有少量生物氣生產，在海上則有甲烷水合物以及台南盆地的氣藏。熱成熟氣的形成，係地層中所含的有機物受埋深而來的高溫被裂解產生，因此其分佈受到地質架構的演化及伴隨而來的沉積形態以及所含有機物類型有密切的影響。台灣西北部各天然氣田裡的天然氣經由同位素分析及運用組成分析，均顯示來自陸源有機物。而臺灣主要油氣田之所在位置也正是煤層展佈的範圍，然含煤地層生產油氣的層數也佔全部油氣生產層數一半以上。台灣地區所發現油氣的特性及環境與大陸東部海域所發現的油氣的分佈規律相同，那就是在大陸近岸及陸上主要係以始新世之湖盆所產生的油氣為主，往外則為含煤三角洲所產生的大量油氣。在大陸東南岸即南中國海的北緣，天然氣主要是來自漸新世的含煤三角洲。臺灣煤之油氣生成潛能，相較國外造成巨型油氣田的煤毫不遜色，且其中有部份煤樣具有代表產油潛能的高氫指數。一般海相沉積的地層因沉積環境含氧量高有機物並不易被保存，此外有些地層還存在沉積速率過快，在水體中的有機物產率有限的情況下，能被保存下來的有機物會被無機物所稀釋。故地層中有機物含量偏低，因此難以成為有效的熱成熟油氣供應源。在台灣南部平原地區，因地層未受造山運動影響，生物氣則普遍存在，在官田證實有此類氣藏生產，儘管其數量不多。但由於外海鑽探結果顯示外陸棚沉積係以泥為主，換言之自漸新統以上均以泥為主，數千公尺厚的泥層可望保留住相當數量生物氣如台南外海，然無法像以色列外海的那些構造那般豐厚。

Hydrocarbon reserves found around Taiwan are almost entirely natural gas, with only a small amount condensate. The most of it, up to more than 50 billion cubic meters, geographically distribute in northwestern Taiwan. Billions cubic meters was discovered in the Tainan basin offshore Taiwan. But only a small amount hydrocarbon was discovered in southern Taiwan. Most of natural gas are the thermal mature gas generated from the terrestrial organic matters (higher plants), which is classified as the type three organic matters. The other is biological gas. A small amount of this has been produced in southern Taiwan. Alternative it wide spread as gas hydrate in the offshore of southwestern Taiwan. Thermal gas is a product of organic matter in stratum which is cracked by the high temperature during buried deep. Its distribution is affected by the evolution of the geologic structure, the accompanying sedimentary characters and the type of organic matter content. The result of analyses based on gas isotope and the gas composition reveal that natural gas reserved in northwestern Taiwan are derived from terrestrial organic matter. The location of the main gas fields in northwestern Taiwan is just overlap on the area of coal seam distribution. Therefore, more than half of gas-producing layers discover in the coal-bearing strata. The characteristics and environment of gas found in the Taiwan region are the same as those found in the east coastal areas of mainland China. In the eastern part of onshore and the nearshore area of mainland China, hydrocarbons mainly derive from the Eocene lake basin. But outside of these zones a huge amount of oil and gas generate from coal-bearing delta system. Generally speaking in the northern margin of the South China Sea, natural gas is mainly generated from the Oligocene coal-bearing delta. The hydrocarbon generation potential of Taiwan coals is as good as that of the giant gas fields, and some of the coal samples have high hydrogen index of oil prong. Organic matter is not so easy to be preserved in general marine strata due to high oxygen content in water column during deposit, and limited organic matter in the water diluted by inorganic sediment as too fast deposition rate. Therefore, too low organic matter content in the marine strata distributed in southwest Taiwan to generate enough hydrocarbon as an effective thermal hydrocarbon source. These marine strata are not disturbed heavily by orogeny, therefore it could be preserved the biogenic gas in the idea trap in the deeper part. Even though the reserves found is not so big enough. But mud dominated in the outer shelf sediment has been proved by drilling in so many wells in the southwest offshore Taiwan. In other words, these mud layers with thousands meters thickness overlaying on the Oligocene sand is expected to trap a considerable amount of biological gas such as the Tainan basin. Though it could not as rich as those reserves in the offshore of Israel.

1. 沈俊卿,吳素慧,溫大任,林殷田,莫慧偵,胡錦城,王明惠,張錦澤,楊志成,陳若玲,蕭良堅(2014)。中國石油股份有限公司經濟部能源局103年度補助計畫期末報告中國石油股份有限公司經濟部能源局103年度補助計畫期末報告,中國石油股份有限公司經濟部能源局。
2. 沈俊卿,孫美蓉,邱仲信(1994)。中國石油公司探採研究所年度研究報告中國石油公司探採研究所年度研究報告,中國石油公司探採研究所。
3. 沈俊卿,郭政隆(1991)。中國石油公司探採研究所年度研究報告中國石油公司探採研究所年度研究報告,中國石油公司探採研究所。
4. 邱仲信,郭政隆,吳素慧,林麗華,沈俊卿,周次雄(1996)。中油公司探採研究所八十五年度研究報告中油公司探採研究所八十五年度研究報告,中油公司探採研究所。
5. 孫智賢(2005)。中油探採研究所九十四年度專題研究報告中油探採研究所九十四年度專題研究報告,中油探採研究所。
6. 孫智賢,郭政隆,吳素慧(2006)。台灣新第三紀煤系地層碳與氫同位素在油岩對比應用上之研究。探採研究彙報，28，443。
7. 張錦澤,林麗華,郭政隆(2006)。台灣新第三紀煤系地層輕碳氫化合物在油岩對比應用上之解釋。探採研究彙報，28，495。
8. 郭政隆,沈俊卿,吳素慧,張錦澤,林麗華,孫智賢(2005)。經濟部石油基金獎勵石油開發技術研究發展計畫經濟部石油基金獎勵石油開發技術研究發展計畫,經濟部。
9. 溫大任,莫慧偵,楊志成,蕭良堅,邱仲信,吳素慧(2016)。經濟部石油基金獎勵石油開發技術研究發展計畫經濟部石油基金獎勵石油開發技術研究發展計畫,經濟部。