雄安新区雾迷山组岩溶热储成储机制及发育模式

Mechanism and development model of karst reservoir in the Wumishan Formation in Xiong’an New Area

雄安新区雾迷山组地热资源丰富,研究其岩溶热储特征及其形成机理对于雄安新区清洁地热资源的开发利用具有重要的理论意义和实用价值。前人已经对该区雾迷山组油气储集层的分布、古岩溶、成岩作用、储集空间等特征做过一定的研究,但对于该区雾迷山组地热资源的成储机制、特别是3期岩溶等成岩特征尚缺乏系统性的研究。充分利用野外露头、岩心、薄片和测录井等地质及地球物理资料,并结合区域地质背景的分析,对雄安新区雾迷山组的岩石学特征、成岩作用、岩溶热储的成储机制进行了深入研究,并建立了雄安新区雾迷山组岩溶热储的发育模式。结果表明:(1)雄安新区雾迷山组主要岩性为白云岩,主要的储集空间为次生孔隙和构造缝—构造溶蚀缝,热储孔渗变化较大;(2)雄安新区最主要的建设性成岩作用是3种溶蚀作用,包括同生—准同生溶蚀、表生溶蚀和埋藏溶蚀,主要破坏性成岩作用是压实作用和胶结作用;(3)根据构造演化、岩心及测井资料,将表生溶蚀作用划分为3期,分别是芹峪期、印支期和燕山—喜山期。芹峪期雾迷山组局部出露遭受淋滤,形成的溶孔经后期改造后不易识别;印支期大部分区域抬升并遭受淋滤,形成高孔渗储集层,后期遭受了进一步改造;燕山—喜山期是雄安新区规模最大、影响最广泛的表生岩溶作用形成期,对前期的储集层进一步淋滤、改造,形成大范围的优质储集层。最后提出了雄安新区雾迷山组优质岩溶热储的成储机制与模式,指出了岩溶热储的有利发育区。

There are abundant geothermal resources in the Wumishan Formation of Xiong’an New Area. Studying the characteristics and main controlling factors of high-quality karstic geothermal reservoirs in the Wumishan Formation is the foundation of the geothermal resources exploration. Previous work has analyzed the distribution, diagenesis, reservoir space of the karst reservoir of the Wumishan Formation. However, there are limited work has been carried to understand the reservoir mechanism, especially for karst characteristics of three different stages. We analyzed the diagenesis types and the transformation mechanism of the Wumishan Formation in study area, based on field outcrops core data, thin section and logging data. The results show that:(1)The main lithology in the study area is dolomite, and the main storage spaces are secondary pores and structural-dissolution cracks.(2)The most constructive diagenesis is epigenetic dissolution, the most destructive diagenesis is compaction and cementation.(3)We divide epigenetic dissolution into three stages: including Qinyu stage, Indosinian stage and Yanshanian-Himalayan stage. Local outcrops of the Wumishan Formation during the Qinyu Movement were leached, however, the formed dissolved pores are not easy to identify after later rework. During Indosinian movement, most of study areas were uplifted and leached, which were further reworked. The Yanshanian-Himalayan period was the epigenetic karstification with the largest scale and the most extensive influence in the study area, which further leached and reworked the earlier reservoirs to form large-scale high-quality reservoirs. Finally, we raised the formation mechanism and model of high-quality karst thermal storage in the Wumihsan formation in Xiong’an New Area, and pointed out the favorite area of karst reservoir.