地块－海槽边缘带成油成气新概念

NEW CONCEPTION OF OIL AND GAS FORMATION FROM THE MARGINAL ZONE OF MASSIF-TROUGH IN NORTHWEST CHINA

对准噶尔、塔里木等盆地沉积环境的研究表明，古生代时，中国西北区为海相沉积，沉积盆地的基底是一些离散的古老结晶地块，其上海水侵漫，地块之间为大洋或窄大洋的海槽。地块之间的海槽或地块与海槽过渡的边缘带盆地是油气形成的有利地带。在海槽遭受压缩褶皱而回返的造山过程中，＂地块－海槽＂体系发生转化，形成中新生代＂山系－盆地＂的陆相沉积体系。边缘带的油气源岩系被埋藏在盆地外围的山系之下。但其中形成的部分油气已运移到盆地内的储集层中聚集，形成＂外生内储＂的油气藏。在这种类型的盆地中，存在陆相生油和海相生油、＂内生内储＂和＂外生内储＂的两类生油岩系和两种生储组合配置体系。这一油气形成分布的理论，已不断地被油气地球化学研究和勘探实践所证实。＂地块－海槽＂边缘带油气形成观点的提出，突破了以现今盆地为界限研究古生代油气形成分布规律的传统观念，增大了中国西北区可以发现的油气资源量，扩展了找油找气的新领域，具有十分重要的意义。

The comprehensive studies on the sedimentary settings in Jungar and Tarim Basins shown clearly that China's northwestern was mainly sedimentary marine environments and the basements of sedimentary basins were a number of separated ancient crystalline massifs covered by sea water,among which there were palaeo-ocean trough or/and narrow palaeo-ocean trough.The marginal basins along the trough between different massifs or the marginal zone between massif and ocean trough are favorable for oil and gas generation. During the processes of mountain-building with the compressional folding to the ocean trough,the ancient system of MassifTrough transformed from the Palaeozoic marine environments to the Meso-Cenozoic continental sedimentary system of Mountain-Basin, during which time the ancient series of marine source rocks deposited in the marginal basins were bund under the mountains around the basins. And the oil and gas generated from the source rocks have been partly migrated and accumulated into reservoir beds in the basins, which consists of the oil and gas accumulation type so-called'out-generating and inner-reservoiring'. Within this kind of basins, there coexist of two series of source rocks: marine one and continental one, and two kinds of combination complexes of petroleum generating and reservoiring: 'inner generating-inner reservoiring' and 'out generating-inner reservoiring'. This new theory or model of petroleum formation and occurrences has been proved not only by the result of our recent petroleum geochemical research but also by the practice of exploration in some regions. The new conception about petroleum generation from Massif-Trough's marginal zone has been out of the traditional concepts to study on the formation and occurrence of the Palaeozoic petroleum limited by the modern basins, which could be to increase potential petroleum resources discovered and to enlarge new fields for finding oils and gases in Northwest China so that the highly meaningful importance should be come out.