断裂控制的非暴露型大气水岩溶作用模式——以塔北Ym2构造奥陶系碳酸盐岩储层为例

岩溶储层在碳酸盐岩储层中占有重要的地位,但过去一直认为表生期碳酸盐岩地层抬升至地表受大气水潜水面控制的岩溶作用是其主要成因.本文在充分认识塔北英买2地区构造地质背景的基础上,通过岩石学、地球化学及其与岩溶成因和控制因素关系的综合分析,提出在地层沉积序列完整的内幕区也可形成大气水岩溶作用改造的缝洞型储层.以岩芯和薄片观察...

A Fault-controlled Non-exposed Meteoric Karstification: A Case Study of Ordovician Carbonate Reservoir at StructureYm 2, Tarim Basin, Northwest China

Karst reservoir takes an important role in the carbonate reservoir, whose primary formation mechanism, however, has been considering as the karstification controlled by phreatic water table. In this paper, based on the knowledge of geological setting of Ym2 area in Tabei uplift, in combination with the integrated analysis of lithology, geochemistry and the controlling factors of karstification, it has been believed that fracture-cavern reservoir could be formed in carbonate strata by the karstification in the area with the continued depositional sequence. Based on the observation of cores and thinsections, the analysis of geochemistries, such as carbon and oxygen stable isotope, strontium isotope composition, rare earth element, electroprobe, cathodolumine- scene, and fluid inclusion, etc, has been maken on the different types of calcites, and furthermore, the properties and provenance of the diagenetic fluids has been analyzed, and it has been concluded that the meteoric water is the main karst fluid, which exerted the primary effects on the formation of porosities, whereas hydrothermal fluid just modified the reservoir lately. Based on the analysis of the relationship between the tectonic evolution and formation of structure and development of strike-slip faults, it could be known that the uplift of structure and development of strike-slip faults is prerequisite to the karsitification. Furthermore, a new structure and fault-controlled meteoric karstification is proposed, which occurred by meteoric water descending continuously into the fracture systems within the carbonate strata along the faults through the overlaid siliciclastic beds. This new karstification promoted the knowledge of formation machenism of carbonate reservoir.