查干凹陷油气地质特征与勘探发现

Petroleum geologic features and exploration discovery in Chagan sag

查干凹陷是银根—额济纳旗盆地勘探程度较高的凹陷之一,由于受火山岩和构造多期活动的影响,地质条件十分复杂,同时凹陷储集砂体薄、横向变化快,寻找优质储量的难度相当大。通过对查干凹陷油气地质特征的综合分析,认为烃源岩展布控制了油气分布,油气具有近源环洼分布的特点;凹陷的结构控制了油气的优势运移方向,长期活动的断层提供了油气运移的有效通道,有效储层控制了油气的富集程度,具有自生自储和下生上储两种油气成藏模式。在这一认识指导下,查干凹陷发现了上、中、下3套成藏组合、5套含油层系,探明了吉祥、如意两个油田,取得了丰硕的勘探成果。

The Chagan sag is one of sags that are highly explored in the Yingen-Ejina Banner Basin. Affected by volcanic rock and multi-stage tectonic activities, its geological conditions are complex, and its reservoir sands are thin and quickly change in lateral direction, which make it difficult to find high-quality reserves. Through comprehensive analysis of the petroleum geologic features in the Chagan sag, it is believed that the source rock distribution controls the oil and gas distribution - oil and gas are mainly distributed near source and around depression. The structure of the sag controls the dominant migration direction of oil and gas, the long-active faults provide effective channels for oil and gas migration, and the effective reservoir controls the oil and gas enrichment degree. Two hydrocarbon accumulation patterns are formed, i.e. self-generating and self-preserving type, and lower-generating and upper-preserving type. On this basis, fruitful exploration results have been achieved in the Chagan sag. For example, 3 hydrocarbon accumulation associations （upper, middle and lower） and 5 oil-bearing series are found and the Jixiang and Ruyi oilfields are proven.