Reservoir characteristics and karst model of Ordovician Yingshan Formation in Yubei area, Tarim Basin

By means of core observation, statistics of pore, hole and fraction, logging, and diagenesis, researches are carried out, indicating that the reservoir space types and property of the weathering crust of the Ying-shan Formation are different among different structures in the Yubei area. The superposition of multi-period karst took place in the weathering crust of the north-east trending structure in the Yubei area, and the reservoir spaces such as cave, hole and fracture developed, showing good reservoir property. In the Pingtai area and the Yudong fault depression, only the middle Caledonian stage Ⅰ karsts generated with poorer reservoir property, mainly of fractures and weak solution pores. Because of dolomitization, bedding solution pore and fracture reservoirs deve-loped in karst insider of the lower member of the Yingshan Formation, and pores and holes occurred alone, showing poor connectivity and no/half filling (oil or calcite). The evolution models of the Yingshan Formation karst reservoirs were established. And the tectonic movement of the middle-late Caledonian and early Hercynian controlled ancient landform and influenced the karst reservoir development in the Yabei area.