塔里木新生代复合再生前陆盆地构造特征与油气

Tectonic Characteristics and Petroleum Prospects of Cenozoic Compound Rejuvenated Foreland Basins in Tarim

再生前陆盆地是针对中国地质特点研究提出的,与周缘前陆盆地、弧后前陆盆地并列的第三种典型前陆盆地类型。本文在讨论再生前陆盆地概念的基础上,以塔里木新生代复合再生前陆盆地为例,从其形成的构造背景、构造—沉积演化、断裂褶皱构造变形,以及基本石油地质条件与含油气性等方面,详细阐述了再生前陆盆地的基本构造特征、构造变形样式、优越的油气地质条件及良好的油气勘探前景,以便今后深入研究这一根据中国地质特点提出的前陆盆地新类型,指导塔里木盆地以及中国西部相关盆地的油气勘探。

The term 'rejuvenated foreland basin' is proposed in view of the geological features of China , which is the third important type of foreland basins. The other two are the peripheral foreland and back-arc foreland basins. This type of basins belongs to the internal structure of a conti- nental plate. With the new concept explained, this paper discusses in detail the basic structural features and deformation styles as well as favourable conditions and prospects for oil and gas in the basins by taking the Cenozoic compound rejuvenated foreland basins in Tarim as an example. This may provide guidance for oil and gas exploration in the new type of basins in Tarim and relevant basins in western China. It could be concluded as follows:①the Kuqa and southwest Tarim rejuvenated foreland basins are formed in front of the Tianshan and Kunlun Mountains since Cenozoic, both are typical rejuvenated foreland basins compounded on a plane. Their formation is mainly related to the early structural traces such as palaeo-A subduction existing in the southern margin of basins during Silurian to Devonian and Triassic and the northern margin during Permian, and also the collision between the India and Eurasia plates and their continuous movement. It is a long-distance effect of the collision that resulted in the revival and regeneration of the palaeo-A type subduction in Tarim in the early time. ② The evolution of Cenozoic rejuvenated foreland basins in Tarim could be divided into four stages; The first is the development stage of pre-rejuvenated foreland basins during the Palaeocene and Eocene as well as the early Tertiary. The second is the early stage of rejuvenated foreland basins from Oligocene to late Tertiary. The third is the development stage of rejuvenated foreland basins from Kangcun age to Kuqa age in late Tertiary, and the forth is the structurally deformation stage from the end of Kangcun age to the early Pleistocene. ③ The structural deformation styles of rejuvenated foreland basins in Tarim are characterized by rejuvenated foreland thrust belts, frontal uplifting and structures related to strike-slip and other activities. Among them, the rejuvenated foreland thrust belts include the Kuqa, southwest Tarim and Kalpin thrust belts, which are all Meso -Cenozoic complex structural belts of faults and folds. ④ The rejuvenated foreland basins in Tarim have favourable conditions for oil and gas. The source rocks are coalbeds and lacustrine mud-stones developed in Mesozoic sequences of rejuvenated foreland basins, and the reservoirs are found not only in sequences of pre-rejuvenated foreland basins, but also in the rejuvenated foreland basins. They are mainly sandbodies of great thickness of fluvial and shallow lacustrine fa-cies. Two regional caprocks are deposited in Jurassic coalbeds and lower Tertiary gypsiferous-saline rocks. In recent years, a great deal of progress has been made in natural gas exploration in rejuvenated foreland basins in Tarim, and a large quantity of natural gas reserves have been proved and a number of large-medium gas fields discovered, which demonstrate the good potential for oil and gas exploration in rejuvenated foreland basins in Tarim.