中国各类陆相盆地斜坡区大中型岩性型油气田形成特征

我国陆相含油气盆地斜坡区大中型岩性型油气田主要发育于4类盆地之中:a)陕甘宁中生界稳定克拉通盆地具有中等油气资源丰度,盆地东北部的大型河流-三角洲砂体成为大型汇烃系统,将西南部生烃中心的油气源源不断地导向盆地东北部,在燕山Ⅳ幕东部强烈隆升改造作用下,呈南北向展布的盆地东北部三角洲砂体向东尖灭,形成大中型岩性油气田;b)松辽盆地为晚白垩世大型热衰减坳陷盆地,具有高—特高油气资源丰度,东部斜坡区发生反转掀斜改造,使纵向叠置、呈径向展布的大中型三角洲砂体与区域性断层及深部隆起复合形成大中型岩性-断层型油气田;c)准噶尔、川西、塔里木等中新生代大型前陆盆地,主力凹陷常发育大中型汇烃单元,且具有中等油气资源丰度,其斜坡区发育呈径向展布的一系列中小型裙边状扇体,配合斜坡区的大型古隆起背景、地层超覆尖灭和断层,形成大中型岩性型油气田;d)我国东部中新生界张性断陷盆地构造分割性极强,以发育小型汇烃单元为主,在具有高—特高油气资源丰度的凹陷,其斜坡区坡折带纵向叠置的大型扇三角洲及水下冲积扇体,与断层、火山岩体、泥底辟等叠合形成大中型岩性型油气藏. 

FORMATION FEATURES OF MIDDLE-LARGE SCALE LITHOLOGIC OIL AND GAS FIELDS IN THE SLOPES OF MAIN TERRESTRIAL OIL BASINS OF CHINA

Various kinds of terrestrial oil basins are evolved in China,and the formation features of middle-large scale lithologic oil and gas fields in the slopes of the basins are different.The structural partition in the extensional faulted Meso-Cenozoic basins is strong.And in the sags with high-very high hydrocarbon abundance,large types of radial distributed fan deltas and underwater alluvial fans are often superposed in slope areas,and middle-large scale lithologic complex oil and gas reservoirs are formed under the control of faults,formation overlap and pinchout,igneous rocks,and mud diapir.Middle-large scale hydrocarbon accumulating units are evolved in the huge Late Cretaceous Songliao Down-warped Basin which is formed due to heat decreasing,and the basin is of high-very high hydrocarbon abundance.By the controlling of regio-nal faults and bulges from bottom,middle-large scale lithologic-faulted oil reservoirs are formed in the slope areas in which middle-large scale of superposed delta sandstone bodies and tilted and inversed structures are evolved.Large hydrocarbon accumulating units are formed in the steady craton basins such as the Late Paleozoic Ordos Basin and the Mesozoic Shanganning Basin with middle scale of hydrocarbon abundance.The large-middle types of alluvial-delta sandstone bodies at the northeast parts of the basins are always the hydrocarbon accumulating systems receiving hydrocarbon from the hydrocarbon-generating center at the southwest parts of the basins.Under the violent deformation the of Yanshannian-Ⅳmovement,large-middle types of lithologic oil fields are formed in sandstone bodies which distribute in the north-south direction and pinchout eastward.Because the large-middle types of hydrocarbon accumulating units are formed in main sags,the large Mesozoic forland basins such as the Junggar Basin,the West Sichuan Basin and the Tarim Basin are of middle scale hydrocarbon abundance,and a series of middle-small types of skirt-edged fans by radial distribution are formed in the slop areas.And under the background of big existed bulges,formation overlaps and pinchouts as well as faults,lithologic oil fields can be formed in the fans.