The studies of petroleum geologic characteristics, structural unit division and profitable exploration zone selection of the Changtu Sag showed that Cretaceous was well developed in the study area, and the Lower Cretaceous was a main exploration target. The dark mudstones of the Jiufotang Formation, with high organic car-bon abundance, typeⅡ2 kerogen and in mature stage, served as the main source rocks and mainly developed in the north of the sag. There were 3 sets of reservoirs including the Jiufotang, Shahai and Fuxin Formations. The Jiu-fotang reservoirs developed in the north and the south, and belonged to type Ⅱ. 2 kinds of petroleum systems were concluded. As to the 1st kind, hydrocarbon generated and self-stored in the Jiufotang and Shahai Forma-tions. While for the 2nd kind, hydrocarbon generated from the mudstones in the Jiufotang Formation, stored in the sandstones in the Shahai Formation, and capped by the mudstones in the lower part of the Fuxin Formation. The Central Structural Zone, which was adjacent to hydrocarbon generation sag and had many traps, was the tar-get for hydrocarbon migration for a long time, hence was a favorable petroleum exploration zone.%通过对昌图断陷石油地质条件分析、构造单元划分及区带综合评价，认为昌图断陷主要发育白垩系，下白垩统为主要勘探目的层。九佛堂组暗色泥岩为主力烃源，主要分布在北部洼陷带，有机质丰度高、Ⅱ2型干酪根，为成熟烃源岩；发育九佛堂组、沙海组、阜新组3套储层；九佛堂组储层存在南、北2个发育区，为Ⅱ类储层。存在九佛堂组和沙海组自生自储和以九佛堂组泥岩为烃源岩、沙海组砂岩为储层、阜新组下部泥岩为盖层构成的生储盖组合。中央构造带濒临生烃洼陷，长期处于油气运移指向区，圈闭发育，是有利的勘探区带。
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