摘要
///Middle Ordovician organic reefs in Tarim Basin mainly develop in Yijianfang Formation and are chiefly distributed in Tabei and Bachu areas with patch reef in open platform development. There are four Ordovician exploration wells at Wellblock HD23, in which HD17, HD13 and YW2 are found Calathium reefs in drilling, the thickness of the reef is about five meters, the upper and lower strata of the reefs is composed by arene oolitic limestone and gritty limestone. The explanation of 3D seismics at Wellblock HD23 exhibit that there are a thickness anomalous body in the strata of Yijianfang Formation, by analyzing, the anomalous body is the locally anomalous development of calathium reef-banks complex. The reef-banks complex is lateral sectors-connecting and has certain distribution scope and scale.