徐家围子断陷火山岩储层特征及演化规律

储层物性是影响徐家围子断陷火山岩气田天然气聚集的重要因素,理清火山岩储层物性特征及影响因素将有利于指导该区深层火山岩的勘探部署工作。通过岩心、岩屑以及显微结构观测,深入分析了火山岩储层的岩石学特征和储集空间特征,初步探讨了徐家围子断陷营城组火山岩储层的储集空间类型及其演化规律。研究结果表明,徐家围子断陷营城组火山岩储层的储集空间主要有原生孔隙、次生孔隙及裂隙3类,不同的储集空间类型发育部位不同;储集空间的发育受到岩性与岩相的联合控制,喷溢相上部亚相的气孔流纹岩、爆发相热碎屑流亚相的熔结凝灰岩、火山通道相火山颈亚相的角砾熔岩储层物性最好;原生孔隙一般连通性较差,而成岩过程中的微裂隙以及后期的构造缝改善了原生孔隙的连通性;火山岩经历了岩浆冷凝收缩、风化淋滤、有机酸溶蚀以及碳酸溶蚀等作用,形成了原生气孔、冷凝收缩缝、脱玻化孔、长石溶孔、火山灰溶孔等大量的储集空间;构造裂隙与地下流体充注的耦合关系影响着储层的溶蚀作用。

Reservoir characteristics and evolution of volcanic rocks in Xujiaweizi fault depression

The reservoir property is the important factor for gas accumulation in the volcanic gas field of the Xujiaweizi fault depression. The core, debris and microscope structures of the volcanic rocks were observed, and the features of reservoir spaces were analyzed. The results show that the reservoir spaces contain three kinds of primary pores, secondary pores and facture-pores developed in the different places. The development of the reservoir spaces are dominated by lithology and lithofacies. The reservoirs in the air hole rhyolite of the upper lava subfacies, flood tuff in the heat clastic fluid explosive subfacies, breccia sandstone in the lava neck volcanic conduit subfacies are well developed. The primary pores are short of connectivity, which was improved by the diagenetic and paulopost fractures. The pores of the volcanic rocks became the primary gas pores, condensed shrinkage joint, devitrification emposieu, arkosic dissolved pores and volcanic ash-dissolved pores under the actions of magma condensation, weathering and leaching, organic acid and carbonate corrosion. The coupling action of the fractures with the displacement and groundwater injection impacted the denudation of the volcanic reservoirs.