Abstract:

The oil and gas reservoir in the middle fault depression belt of Hailar-Tamtsag basin shows great potential and with large scale. They distribute widespread in the Cretaceous sequences. Although it has been provided with favorable geology and accumulation conditions of oil and gas, and serves as the key field of oil and gas exploration in the future, the formation and accumulation rules are not clear. Based on integrated statistic analysis and geological data, we focus on the formation, distribution, and accumulation of oil and gas reservoir in the area. The controlling factors are as follows. First, multi-period structural movement controlled the basin framework and established the structural pattern of depression with rich oil accumulation. Second, different tectonic phase controlled the sedimentary infilling evolution. The fault slope break belt and structural transfer zone controlled the fan body distribution. All of them supply advantageous reservoir for oil and gas accumulation with great scale. Third, clastic rock with high content of volcanic substance was easy to dissolve, which resulted in the development of secondary pore, and it created beneficial condition for the formation of favorable reservoirs. We therefore that concluded that the concave uplift belt of composite half-graben fault depression and the great gentle slope fault terrace belt served as favorable oil and gas reservoir. Hydrocarbon kitchen controlled the distribution of oil and gas reservoir. The favorable facies belt was an important factor for oil and gas enrichment. The results may be useful for the consideration in similar petroleum system exploration.

Key words: Hailer-Tamtsag basin, middle fault depression belt, oil and gas reservoir, formation conditions, accumulation rule, distribution characteristic