银额盆地查干凹陷基底岩性特征及勘探方向探讨
Discussion on the Basement Lithological Characteristics and Exploration Targets of Chagan Depression in Yingen-Ejinaqi Basin

近年来银额盆地拐子湖凹陷拐6井基底大理岩缝洞型储层试油获高产，吉格达凹陷蒙额参3井基底花岗岩裂缝型储层试油获工业油流，为查干凹陷潜山油气藏的勘探指明了方向，寻找基底缝洞型储层成为查干凹陷潜山勘探的关键因素。基于基底岩心薄片鉴定和测井资料，明确了查干凹陷发育变质岩基底，已发现变质玄武岩、蛇纹石化橄榄岩、板岩、变质砂岩和片麻岩五种岩性，不同岩性在密度、声波、伽马和深感应曲线上具有明显差异。对比周边野外露头剖面和邻区白云凹陷白云1井钻探情况，认为查干凹陷基底地层归属石炭系阿木山组一段。结合地层倾角测井资料，明确基底为北东走向，意4井西北方向发育阿木山组一段上部地层，以板岩为主，夹变质砂岩。位于毛西断层上升盘的毛墩次凸主要发育片麻岩。毛西断层意4井东南方向至毛西断层发育阿木山组一段下部地层，为大理岩与变质火山岩互层，为基底有利储层发育区，位于毛西断层下降盘的乌力吉构造带为查干凹陷潜山勘探有利区。
In recent years, high production was obtained in the fracture-cavern marble reservoir of well Guai 6 in the Guaizihu depression of Yingen-Ejinaqi basin and industrial production was obtained in the Granite reservoir of well Meng’ecan 3 in the Jigeda depression of Yingen-Ejinaqi basin, which indicated the direction for the hydrocarbon exploration of buried hill reservoirs in Chagan depression, and the key point in buried hill exploration was looking for high-quality reservoir of fracture-cavern reservoir. Based on the core thin section identification and logging data, the metamorphic rock basement of Chagan depression was defined. Five lithologies of metamorphic basalt, serpentinized peridotite, slate, metamorphic sandstone and gneiss had been found, which were typical of density, acoustic, gamma and depth response curves. Compared to the outcrop profile of the surrounding field and the drilling situation of well Baiyun 1 in the Baiyun depression of the adjacent area, it was believed that the basement strata in Chagan depression belong to the first member of the Amushan formation, Carboniferous. Combined with diplog data, it was clear that the basement is NNE strike. Based on the above analysis, it is predicted that the upper of the first member of the Amushan formation developed in the west-north of well Yi 4 of the western sag in Chagan depression, and the main lithological was slate, mixed with metamorphic sandstone. And in the rising wall of Maoxi fault, gneiss had been found in the Maodun sub-bulge. The bottom of the first member of the Amushan formation was developed in the Wuliji tectonic belt between the east-south of well Yi 4 and Maodun sub-bulge, and the lithological was marble and metamorphic basalt. In Chagan depression, the Wuliji structural in the descending wall of Maoxi fault was a favorable exploration area for buried hill because of the favorable reservoir.