特提斯构造域与油气勘探

Tethyan tectonic domain and petroleum exploration

关键词:  特提斯构造域  油气  勘探建议

Key words:  Tethyan tectonic domain  oil and gas  exploration proposal

摘要:

Klemme和Ulmishek(1991)将全球已探明的油气可采储量分为四大域:特提斯域、北方欧亚域、南方冈瓦纳域和太平洋域。其中特提斯域内的油气储量主要分布在中东地区。
板块学说进入大陆之后,给特提斯的研究带来了新的启示。阿尔卑斯-喜马拉雅造山带是新特提斯海消亡的产物,而现今提出的古特提斯和基梅里造山带已突破Suess原提出的时空范围,其演化时间已延长到古生代,地域上已达亚洲中纬度地区。中国的青藏高原、扬子地块、华北地块及塔里木地块等属于特提斯构造域范围内。特提斯巨型构造域虽然在走向上有明显的分段性,但其形成演化存在可比性。笔者认为以扎格罗斯带为代表的新特提斯可与喜马拉雅新特提斯对比。
阿拉伯地台至扎格罗斯山前坳陷与中国境内青藏高原地质特征有许多相似之处:①发育自寒武纪至第三纪连续沉积了厚度5000～12000m的海相沉积,具典型的被动边缘沉积特征。区内广泛发育侏罗纪至老第三纪的海相沉积;②区内泥盆纪、晚侏罗世、白垩纪及第三纪发育有礁灰岩,二叠纪、三叠纪、侏罗纪、白垩纪及第三纪发育有白云岩、硬石膏、岩盐、滩岩等,在晚侏罗世、早中白垩世及老第三纪始新世均发育有油页岩;③自早古生代至新生代具多元生烃地层单元组合,具多套生、储、盖组合,具多旋回演化历程。
青藏高原有巨厚的沉积建造,特别是中国海相三叠系、侏罗系、白垩系和老第三系分布面积最大、最集中的地区,主要含油气盆地(面积大于10⁴km²)有羌塘、昌都、措勤、比如、日喀则、岗巴-定日、昂拉、库木库里、可可西里等大中型新生代沉积盆地。沉积盆地发育有厚达万米以上的沉积岩系,有丰富的生油岩,并有3～6个生、储、盖层组合,具有良好的生油地质条件。
青藏高原的中新生代沉积盆地上叠在稳定陆块之上,不是统一的造山带。它保存有侏罗纪—白垩纪沉积盆地的原型。自上新世晚期至今,藏北高原上升4000m,它是在一个相对封闭系统下的整体抬升,包含静中动和动中静的哲理。热力学第一定律告诉我们,在一个封闭系统中能量和物质是不能产生和消灭的。喜马拉雅运动的强度被人为地扩大。特提斯域的油气勘探范围应逐渐从新特提斯域走进古特提斯域。

Abstract:

Four petroleum realms of the world have been distinguished by H. D. Klemme and G. F. Ulmishek (1991): Tethyan (dominantly in the Middle East), 17% of the total area and 68% of the original petroleum reserves; Boreal, 28% of the total area and 23% of the original petroleum reserves, South Gondwana, 38% of the total area and 4% of the original petroleum reserves and Pacific, 17% of the total area and 5% of the original petroleum reserves.
Recent advances in plate tectonics provide insight into new areas of research within the Tethyan realm. The Tethyan Ocean is an intercontinental plate characteristic of the oceanic lithospheric crust, and may be composed, according to its development, at least of the Palaeo-Tethys (from the Devonian or Carboniferous to Permian) and Neo-Tethys (from the Triassic to Tertiary). There exists the Cimmerian-Cathaysian palaeocontinental group between Laurasia and Gondwana land. The Alpine-Himalayan orogenic belts are believed to be developed following the termination of the Neo-Tethyan Ocean. However, the temporal and spatial extent of the Palaeo-Tethys and Cimmerides-presented in the text has gone beyond that defined by Suess, i.e. an extension of the area into the mid-latitude regions in Asia and of the time dating back to the Palaeozoic. Furthermore, the Qinghai-Xizang Plateau, Yangtze, North China and Tarim landmasses are all assigned to the Tethyan realm. Although the individual parts within the giant Tethyan tectonic domain are evidently different, they may be compared each other. For example, the Neo-Tethys represented by Zagros may be compared with the Himalayan Neo-Tethys. The striking similarities are outlined as follows. (1) The Cambrian to Tertiary marine sediments 5000-12000 m thick are widely developed, typical of the passive continental margin sediments. The Jurassic to Paleogene marine sediments also occur on a wide range of scales in these areas; (2) The representative sediments recognized in these areas include-reefal limestones during the Devonian, Late Jurassic, Cretaceous and Tertiary; dolostones, anhydrite, rock salts and beach rocks during the Permian, Triassic, Jurassic, Cretaceous and Tertiary, and oil shales during the Late Jurassic, Early Cretaceous and Eocene of the Paleogene, and (3) The multiple hydrocarbon-bearing stratigraphic associations and source-reservoir-seal associations indicate a history of polycyclic evolution from the Early Palaeozoic to Cenozoic.
The Qinghai-Xizang Plateau is occupied by the tremendous thickness of the marine sediments especially the Triassic, Jurassic, Cretaceous and Paleogene strata. The major petroleum basins with an area of more than 10⁴ km² include the mediumand large-sized basins such as Qiangtang, Qamdo, Coqen, Biru, Xigaze, GambaTingri, Ngangla, Kumkol, Hoh Xil, Lanping-Simao, Xichang and Chuxiong Basins. These basins immediately overlain upon stable landmasses are characterized by thick sedimentary rock series (more than ten thousand metres) and effective petroleum source rocks with several source-reservoir-seal associations, and thus exhibit excellent geological conditions for oil and gas accumulation. The northern plateau has been uplifted by 4000 m since the late Pliocene, and the uplift is still going on within a relatively enclosed system. According to the first law of thermodynamics, it is im possible for the energy and matter to be created and eliminated in an enclosed system. In this respect, particular attention should be drawn to the Palaeo-Tethyan realm for the exploration plays of oil and gas throughout the Tethyan realm.