阿富汗北部阿姆河盆地东部油气差异分布控制因素研究

Controlling Factors of the Oil and Gas Differential Distribution in the East of Amu-Darya Basin of Northern Afghanistan

阿富汗北部阿姆河盆地油气分布具有显著的差异性,北部和南部分别主要是气藏和油藏,而中间过渡地段油气兼有,为带油环的气藏。通过分析油气成藏地质条件,探讨了这种油气差异分布的控制因素。结果发现圈闭充满度、油气组分、储盖组合南北不同。由北向南圈闭充满度有逐渐降低的趋势;CH4含量逐渐变高,而CO2和H2S含量逐渐变低。以上侏罗统膏盐层为界,北部发育盐下上侏罗统碳酸盐岩储盖组合,而南部发育盐上下白垩统碎屑岩储盖组合,中间过渡地段盐下及盐上储盖组合均发育。膏盐盖层的分布范围是控制油气差异分布的关键因素。据此建立了油气差异分布模式,对研究区不同区域的油气勘探目标进行评价,指出:在北部盐岩分布区,主要寻找上侏罗统气藏;在南部盐岩缺失区,寻找的重点则是下白垩统油藏;在两者之间,上侏罗统气藏和下白垩统气藏及油藏均是潜在的目标。

In Amu-Darya Basin of Northern Afghanistan, the oil and gas distribution shows significant difference,i, e. ,gas pools are located in the north and the oil ones in the south,while in between arc the oil pools and gas pools with oil ring. By analyzing the geological elements of oil and gas accumulation.the controlling factors of oil and gas differential distribution are approached. From north to south, trap fill, gas component and reservoir-cap assemblage differ specially. Southward, the trap fill and content of CO2 decease,while CH4 increases. Bounded by the Upper Jurassic sah,the reservoir-cap assemblage in the north and south is subsah Upper Jurassic carbonate and supra-sah l.ower Cretaceous clastic ones, respectively, and in-between both assemblages develop. The distribution range of gypsum and salt is the key factor con trolling the differential distribution of oil and gas. Then the corresponding mode is established and the exploration targets in the research area are evaluated, which indicate that in the north of the research area where sah exists the Upper Jurassic gas pools are the targets,while in the south where anhydrite is absent the oil pools shoulcl be focused, and in between both Upper Jurassic gas pools and I.ower Cretaceous oil pools and gas pools are the potential targets.