Abstract: This paper studies the development characteristics and control factors of trachyte fractures developed in the underwater environment in the Oulituozi region, the Liaohe Basin, using cores, thin sections and imaging logging data etc., with the intent to analyze the formation mechanism of trachyte reservoirs for supporting oil and gas exploration and development. The study results show:(1) four types of fractures including blasting fractures, shrinkage fractures, tectonic fractures and dissolution fractures are developed in the trachyte; (2) blasting fractures, shrinkage fractures and dissolution fracturesare highly filled, making most of them ineffective; and tectonic fractures play the major role to reform the trachyte to reservoir; (3) tectonic location is an important factor that controls the development of fractures which almost occur in a well-developed fault zone, the frontal belt of the upthrown side of a reverse fault and near major faults; (4) the single-layer thickness is positively related to the fracture development, that is, the thicker the single layer is, the more developed fractures are in the trachyte.

Key words: Liaohe Basin, Oulituozi, trachyte, underwater environment, fracture