台灣西南海域深水地區探勘願景

Prospect in Deepwater Exploration in Offshore Southwestern Taiwan

吳明賢(Ming-Shyan Wu) ； 古月萍(Yueh-Ping Ku) ； 沈俊卿(Jun-Chin Shen) ； 王明惠(Ming-Huei Wang) ； 吳素慧(Suh-Huey Wu) ； 邱仲信(Jong-Hsin Chiu) ； 陳怡如(Yi-Ru Chen) ； 涂嘉勝(Chia-Sheng Tu) ； 張峻瑋(Jun-We Zhang) ； 翁榮南(Ron-Nan Wong) ； 李元偉(Yuan-Wei Li)

《石油季刊》 49卷3期 (2013/09) Pp. 1-16

摘要

盆地深水區的石油探勘一直是世界油公司擴展油氣藏的重要目標之一，90年代由於層序地層學的發展導致了深水探勘的革命，西非地區掀起了一股深水探勘的熱浪和耀眼的成績。隨著海上油氣探勘技術的進步已征服了具有挑戰性的環境，可以預期的是每年都會有重大的油氣發現。台潮石油合約區東南測勘區是由中央隆起帶劃分南北兩個凹陷帶，形成二凹一隆的基本構造形式。北部凹陷條件比較好，因為它具有一定的封閉性。預估油氣生成量經模擬結果發現，東南測勘區汕頭凹陷文昌組生油源岩的排油量為9.85億噸，約相當72.2億桶的原油。文昌組生油源岩油氣資源量為1.97億噸，約相當14.4億桶的原油。東南測勘區內主要發現有九個主要的構造目標，其中以汕頭A構造成為本研究區最主要的目標構造，具有構造與低位扇的雙重目標組合。台南盆地南緣深水區、台潮石油合約區東南測勘區及珠江口盆地白雲凹陷展現同樣的構造形式；位於珠江口盆地中央隆起區之神狐隆起區－番禺低隆起－東沙隆起區－澎湖－北港高區等600公里長的構造壩（名詞引自孟昭彝等（1976））南緣半地塹之裂谷盆地，該盆地經歷了裂谷盆地之構造演化與後期的岩漿活動，酸性火成岩組成的古潛山形成一障蔽島（Barrier Island），其間的距離發育了約50～60公里的斷陷帶（Rift-subsidence Basins Zone），這些斷陷帶岩層的沉積體系都具有23.8～18.5百萬年前之間低位扇（Lowstand Fan）的沉積體系域的共同性。珠江口盆地的白雲凹陷已在這個沉積體系域發現巨量的油氣，而同位在斷陷帶的台潮石油合約區東南測勘區與台南盆地南緣深水區有著同樣的沉積體系，斷陷盆地的潛力是無窮的。然而，唯一需要注意的是不同的斷陷盆地（Rift-subsidence Basin）需要良好的砂岩做為儲集岩，這些儲集岩需要分佈範圍廣、儲集層的厚度厚的低位扇，才能提供封儲油氣所需的儲集層。而裂谷盆地面積的大小及盆底的深淺，係提供成熟的油氣源的基本要素。這兩點是未來研判各盆地是否進行探勘、開發的主要依據。因此，未來台潮合約區東南測勘區之探勘可考慮在汕頭A構造區先進行三維震測，以確保構造的準確性與油氣的資源量的估算，做為未來鑽探與開發的依據。

關鍵字

深水 ； 低位扇 ； 台灣西南外海

並列摘要

Petroleum exploration in deepwater basin is one of the primary targets to expand the oilgas reserves for global oil industries. The development of stratigraphy sequence in 1990s resulted in the revolution in deepwater exploration. Since then, deepwater exploration spreaded into the offshore West Africa, which resulted in the growth of oil and gas findings. The advanced techniques subsequently developed for the offshore oil and gas exploration have overcome the severe environmental challenges. It could be predictable that, the main oil and gas findings will be reported in the following each years.Architecture of explored area, southeastern Taichao Petroleum Contracted and Region, is composed of two depressions and one raise. The two depressions are aligned in the south and north and are separated by the central raise. The evaluated petroleum system in the northern depression is better than the southern one, due to the discrepancy closure conditions of the two depressions. The estimated generation for oil and gas in place, simulated from the source rock, Wenchang Formation, in the Shantou Depression of the explored region, is ca. 9.85 billion metric tones which equals approximately 72.2 billion barrels of crude oil. The resource estimated for the source rock, Wenchang Formation, is ca. 1.97 billion metric tonnes, which equals approximately 14.4 billion barrels of crude oil. Nine leads are recognized in the southeastern explored region. The lead Shantou A is the main prospect, characterized by the structure and the lowstand fan.An identical structural architecture is displayed in the deepwater region of the Tainan Basin, the explored region of the southeastern Taichao Petroleum Contracted Region and the Baiyun Depression of the Pearl River Mouth Basin. A rift basin with half-graben morphology developed in the southern slope of the structural dam (refer to Meng et al. (1976)) that is with 600 km in length extending from the Shenhu uplift in the Pearl River Mouth Basin, through the Panyu Low uplift and the Dongsha raise, to the Penghu-Pekeng rising area. The basin experienced the rift basin structural evolution and the magma activity in later stage. A buried hill composed of acidic igneous rocks acted as a barrier island. A rift-subsidence basins zone was developed in the interval between the southern slope of structural dam and the buried hill. An identical depositional system tract recognized in the strata of the riftsubsidence basins zone is the lowstand fans built up in the age between 23.8 Ma and 18.5 Ma. The exploration of the lowstand fans in the Baiyun Depression of the Pearl River Mouth Basin experienced the findings with large amount of oil and gas. This identical depositional system tract is also recognized in the explored area of southeastern Taichao Petroleum Contracted Region and the deepwater region of southern slope of the Tainan Basin. It can be drawn that, the petroleum potential in the rift-subsidence basins is behind imagine. Nevertheless, one thing that needs to be noticed is, high quality sandstone is an essential to be the reservoir in the rift-subsidence basins. The essentials of reservoir characterization for oil and gas trapping and accumulation are the lowstand fans with the characteristics of widespread in lateral and thick thickness in vertical. Besides, the area and depth of the rift basin are essentials for the generation of matured oil and gas. The two issues are the crucial basis for further determining whether the exploration and development will be continued or not. For raising the assurances of the structural resolution and the resource estimation, the 3D seismic data will be the basis for the future well design and development. Therefore, acquiring the 3D seismic survey in the lead Shantou A might be one of the considerations for next steps to explore the southeastern Taichao contracted and explored region.

並列關鍵字

Deepwater ； Lowstand Fan ； Offshore Southwestern Taiwan