吐鲁番坳陷成油地质条件分析

AN ANALYSIS OF GEOLOGICAL CONDITIONS ABOUT FORMATION OF PETROLEUM POOLS IN TURPAN DEPRESSION

吐鲁番坳陷是一个中新生代沉积坳陷,油气资源丰富。经分析,其油气富集条件有以下几个特征:①主要发育三种类型构造圈闭,其中燕山期形成的构造圈闭最有利;②发育三套储油层系,储层物性主要受成岩后生作用和沉积相影响,砂体次生孔隙发育,大多数属于中孔、低渗透储层。主要产层为上三叠统克拉玛依组和中侏罗统三间房一七克台组,埋深适中,处于成岩后生作用中期Ⅰ阶段,河流或分流河道砂体,成为油气有利聚集场所;③具有三套生油岩系,即上二叠统、下侏罗统八道湾组和中侏罗统七克台组,其中七克台组和上二叠统生油岩为湖相暗色泥岩,有机质类型以偏腐殖的混合型为主;八道湾组生油岩为河流沼泽相煤系地层,有机质类型以腐殖型为主。热演化程度不高,有利于生成液态烃;④坳陷内分布有多种类型油藏,已发现三种类型油藏,即伊拉湖断背斜油藏、台北背斜油藏和胜金口岩性油藏等。

Turpan depression is a Mesozoic-Neozoic depression,in which high oil and gas potential will occur.According to the results of analysis the condi- tions of hydrocarbon accumulation in the depression can be summarized as follows;1.Three dominant types of structural traps are develops,in which the Yanshan stage ones are the most favorable.2.There are three sets of oil-reservoirs.The quality of reservoir is mainly affected by sedimentary facies and diagenesis.The oil bearing sandstones developed secondary pores, so that they are reservoirs with intermediate porosity and low permeability. Production layers are mainly the Karamayi formation in upper Triassic and Sanjianfang—Qidetai formation in Middle Jurassic,which belong to the fluvial and fluvial distributary channel sandstone.The depth,where they are locat- ed is in the I-stage of middle epigenetic diagenesis.3.Three sets of source rock sequences have been found,i.e.upper Permian,Qiketai formation of middle Jurassic which is lacustrine dark shales with humic dominated mixed organic matters,and Badaowen formation of lower Jurassic which is a flu- vial-swamp coal bearing sequence with humic organic matters.They are favourable for liquid hydrocarbon generation because of their low level of evolution.4.There are many types of oil-pools in the depression.We have found so far three types:Yilahu fault anticlinal oil-pool,Taibei anticlinal oil-pool and Shengjinkou stratigraphic oil-pool.