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.