塔里木盆地塔中地区主要构造圈闭形成期分布及成藏意义

Dominant Forming Stages of Structural Traps in Tazhong Area,Tarim Basin:Distribution and Implication for Hydrocarbon Accumulation

通过对塔中地区钻遇奥陶系的60余口井过井地震剖面的精细解释及地震反射截切—上超关系、沉积厚度变化分析,识别出最初形成于晚奥陶世—泥盆纪、石炭纪—早二叠世、早二叠世晚期及中、新生代的四期奥陶系内幕构造圈闭,以及最初形成于石炭纪—早二叠世、早二叠世晚期、晚二叠世、中—晚三叠世及早第三纪末以来的五期石炭系内幕构造圈闭;发现了塔中地区主要构造圈闭的首次形成期呈现由南向北逐渐变晚的总体趋势。构造圈闭形成与成藏配套综合分析表明,该区现今工业性油藏的主要成藏期为二叠纪—早三叠世,而中—晚三叠世及其以后所形成的构造圈闭不利于油藏的形成。认为塔中地区的主力烃源应该来自近邻的满加尔凹陷中—上奥陶统相当于黑土凹组—萨尔干组的层段。

Through fine interpretation and analysis with seismic truncation-onlap and sedimentary thickness change to the seismic sections passing through more than 60 drilled wells in Tazhong area in Tarim basin, the authors has identified 4 stages of internal Ordovician structural traps, which initially formed respectively during Late Ordovician-Devonian, Carboniferous-Early Permian, late Early Permian and Mesozolc-Cenozoic time, and 5 stages of internal Carboniferous traps, which initially formed respectively during Carboniferous-Early Permian, late Early Permian, Late Permian, Middle-Late Triassic and later than Paleogene time. It is found that the initially-forming stages of main structural traps in Tazhong distributed as a gradual later （younger） trend generally from south to north. By comprehensive analysis of coupling trap formation with hydrocarbon accumulation, it is indicated that dominant stage of commercial hydrocarbon accumulation should be during Permian to Early Triassic time, but the structural traps formed later than Early Triassic time are unfavorable for hydrocarbon accumulation. It is suggested that the hydrocarbon in Tazhong area should derive significantly from the neighboring strata corresponding to Heituwa Fro. or Middle-Upper Ordovician Shargan Fm. in Manjiar Sag.