Abstract: The genesis of ultra-deep marine carbonate reservoirs in polycyclic basins in China is characterized by having multiple control factors and multistage hybrid origins. In the northern transitional zone between the Awati and Manjiaer depressions, the ultra-deep carbonate reservoirs of the Ordovician(in the Yingshan and Yijianfang Formations)are overlain by a relatively complete sequence of the Upper Ordovician and Silurian. Since there was no superimposition of multistage unconformities and the exposure period was relatively short, the reservoirs were formed by deep-circulation dissolution and distribute along the fault zones. The development of the ultra-deep Ordovician carbonate reservoirs in the southern transitional zone between the Awati and Manjiaer depressions is controlled by the strength and segmentation of strike-slip fault activity and hydrothermal fluid alteration. Hydrothermal alteration resulted in the formation of hydrothermal dolomite reservoir(in the lower Yingshan Formation in Guchengxu uplift), while hydrothermal metasomasis led to the silicified rock reservoir(in the upper Yingshan Formation in the Shunnan slope area). Hydrothermal alteration also led to the formation of microbial reservoir (in the Yijianfang Formation in the Shunnan to Shuntuo area). Reservoir distribution could be predicted by the geological model of fault-fluid dominated carbonate reservoirs, the specific seismic acquisition and processing, series of forward anisotropy fracture inversion, quantitative volume estimation, poststack seismic characterization, and simulation of tectonic stress field.

Key words: carbonate reservoir, ultra-deep sequence, reservoir genesis, reservoir prediction, transitional zone between the Awati and Manjiaer depressions, Tarim Basin