鲁克沁油气聚集带稠油成藏特点与潜力分析

ANALYSES OF RESERVOIR FORMING CHARACTERISTICS AND EXPLORATION PROSPECTS FOR LUKEQIN HEAVY OIL BELT

吐哈盆地鲁克沁稠油聚集带三叠系稠油主要有两个成藏期,但各成藏期保存条件不一,导致油气稠变方式不同。中侏罗世西山窑期第一成藏期构造带高部位暴露地表,原油遭受地表水影响和严重的生物降解和散失,普遍出现25-降-藿烷;第二成藏期在白垩纪末以后,整个构造带普遍接受沉积,埋藏持续加深,构造活动平稳,但因圈闭类型差,本期成藏原油也发生稠变,主要是以轻组份散失和水溶散失为主,含蜡量相对较高,稠变类型属于运移残留稠油;目前保存的油气主要为第二成藏期聚集。两期稠变油气混合使三叠系油藏原油总体呈现轻微"降解"。据此分析,第二成藏期及其以后,油源条件和油气保存条件好,构造带东部高部位的前侏罗系风化壳具有良好的勘探前景。

Different preservation conditions during the two major reservoir-forming stages of the Triassic heavy oil in Lukeqin accumulation belt in Turpan depression, Tuha basin, led to different oil and gas thickening modes. Since the top part of the first reservoir forming structural belt in Xishangyao age mid-Jurassic exposed to the surface, crude oil here have been subject to surface water influence, severe biodegradation and dissipation, and 25-norhopance generally occurred. In the second reservoir forming stage, which was after late Cretaceous, the whole structural belt received deposits, and buried depth increased continuously, with stable structural movement. The thickening of crude oil was mainly due to the dissipation of light components. With relatively high paraffin content, the crude can be defined as remaining heavy oil after migration. Oil and gas still exist now were mainly accumulated in the second reservoir forming stage. The mixed oil and gas from the two stages make the crude on the whole exhibit slight degradation in the Triassic reservoirs. According to these analyses, oil sources and oil preservation conditions were relatively good in and after the second reservoir forming stage, the early Jurassic weathering crust in the east top part of the structural belt has bright exploration prospects.