Abstract:

 Karst-fracture is important type of main reservoir space of Lower-Middle Ordovician carbonate reservoir in the southwest region of Tahe Oilfield. Based on collected data including core observation, microscopic -identification- of thin slice, SEM, well drilling, deep and shallow counting line and FMI logging, this paper comprehensively identified karstfracture development zone of Lower-Middle Ordovician and indicated the larger difference between developmental characteristics of reservoir fractures and pores and main region of Tahe Oilfield. The half filling and unfilling structure fracture and corroded fissure are the main reservoir space, while high angle and vertical fracture developed, low angle fracture poorly developed; microfracture and moderate fracture developed, microfracture and pores poorly developed in general. The authors pointed out the development region of fractures and pores by the multifactors evaluation method to reservoir.

Key words: Tahe Oilfield, the southwest region, Lower-Middle Ordovician, carbonate reservoir, karst-fracture characteristics