FRACTURE CHARATERISTICS AND DEVELOPMENT INFLUENCING FACTORS OF ORDOVICIAN RESERVOIRS IN THE TAHE OILFIELD

The Tahe oilfield is located in the northeastern Tarim basin,and the Ordovician reservoir of the Tahe oilfield is a fracture-vug reservoir which consists of secondary pore,such as the tectoclases,emposieu,etc.Based on the core samples and well logging data,there are two types of fractures in the Tahe oilfield.One is non-structural fracture which comprises stylolite and diagenetic fracture.The other is structural fracture which comprises horizontal fracture,low-angle fracture and high-angle fracture.The statistical data shows that small fractures,middle fractures and big fractures account for 43.0%,44.6% and 12.4% respectively;horizontal fracture,low-angle fracture and high-angle fracture account for 40.75%,26.50% and 32.75% respectively;full-fill fracture,semi-fill fracture and unfilled fracture account for 56.27%,17.19% and 26.54% respectively.The fracture dip ranges mainly from 300°N to 330°E,secondarily from 0°S to 10°N and from 160°S to 170°E.The favorable tectonic position of the fracture is the structural high,the structural intersection point and the fault development zone.The fracture development will increase by the raise of the brittleness of the formation;the openness of the fracture will decrease by the upgrade of the burial depth.