Abstract: Several types of natural fractures occur in the reservoir of the Leikoupo Formation in Pengzhou area, western Sichuan Basin, and their major controlling factors are very complex.Geological, geophysical and experimental data are integrated to study the genetic types and characteristics of these fractures, and analyze the geologic factors controlling the formation of tectonic factures.In the reservoir of the Leikoupo Formation, the predominant fracture type is tectonic facture, followed by diagenetic fracture.The tectonic factures can be classified into three types:high angle fractures, oblique fractures and low angle fractures.Each type of fracture has its own specific dominant orientation, indicating that they are resulted from multiple stages of tectonic movement.The fractures are effective in general.High angle fractures are all effective, while some low angle fractures and oblique fractures are ineffective.Fractures are highly developed in dolomite, but are poorly developed in limestone.Due to the impacts of differences of fracture genetic mechanisms and the timing of fracture formation and reservoir diagenetic evolution, the development of high angle fractures and oblique fractures are mainly controlled by faults and their disturbed stress field, thickness of rock mechanics layer and physical properties of reservoirs, while that of the low angle fractures are mainly controlled by occurrences of local strata and structures and sedimentation.

Key words: fracture characteristics, tidal-flat facies, carbonate rock, Leikoupo Formation, Pengzhou area, Sichuan Basin