哈山地区位于准噶尔盆地西北缘,形成于陆缘岛弧背景之下,其石炭系-二叠系火山岩储层是油气藏勘探的重点领域。为进一步明确哈山地区石炭系-二叠系火山岩储层的勘探前景,在岩心、薄片鉴定基础上,综合扫描电镜、微米CT、流体包裹体等技术方法,结合储层物性参数、主微量元素分析结果,对该区石炭系-二叠系火山岩储层发育机制展开系统研究。结果表明:(1)哈山地区火山岩储集空间类型主要为溶蚀孔、粒间孔和溶蚀缝,孔隙直径大且连通性较好,但非均质性较强;(2)火山岩岩相、裂缝、风化淋滤和深部热液流体是影响火山岩储层物性的关键因素——溢流相和爆发相是有利储层发育相带,构造抬升和逆冲推覆使推覆体前翼、断层交汇处储层物性更优质,风化淋滤又进一步改善了储层;(3)基于物性-岩相-储集空间联合分析,将哈山地区火山岩储层划分为3类,其中优质储层主要位于逆冲推覆带的“三角”地带。结论认为,哈山地区石炭系-二叠系火山山岩具备发育大规模优质储层的条件,展现出巨大的油气勘探开发潜力。

The Hala’alate Mountain (Hashan) area located in the northwestern margin of the Junggar Basin is associated with an ancient continental margin island arc, where the Carboniferous-Permian (C-P) volcanic rock reservoirs are the main target for oil and gas exploration. To further assess the exploration prospect of the volcanic rock reservoirs we carry out a systematic investigation into the mechanism of reservoir development in Hashan. Core log, thin section, scanning electron microscope, micro CT, fluid inclusion and other techniques are used for the characterization of reservoir rocks, in combination with major and trace element analysis. We find (1) the main pore types in the volcanic rock reservoirs are dissolution pores, intergranular pores and dissolution fractures with large pore-diameter and good connectivity but strong heterogeneity. (2) Volcanic rock facies, fractures, weathering leaching and deep hydrothermal fluid are key factors affecting reservoir quality, where overflow facies and explosive facies are favorable facies belts for reservoir development. Tectonic uplift and thrust napping improve reservoir quality at the front wing of nappes and fault intersections (“Triangle” area), and weathering/leaching contribute to further improvement. (3) Based on the combined analysis of reservoir rock property and lithofacies, the volcanic rock reservoirs are classified into three quality grades. High-quality reservoirs are mainly located in the “Triangle” area of the thrust nappe belt. We conclude that the C-P volcanic rocks in Hashan area has good prospect of forming large-scale, high-quality reservoirs with huge exploration and development potentials.