Abstract: Lucaogou Formation in Middle Permian is one of the main oil-bearing series in Malang Sag of Santanghu Basin. The basic characteristics of the reservoir of the Formation are represented in this paper from the aspects of lithology, pore structures and permeability of the matrix. It proves that the matrix of the Formation has significant reservoir potential and serves as the main reservoir spaces. Based on the data of core description, dip, and imaging logging, thorough description and analysis are conducted on the fracture development characteristics of reservoirs in Lucaogou Formation. The relationship between the fracture and the lithology, stratum thickness, and structural location is figured out, as well as the favorable distribution of the fractures is identified in the Formation. What's more, the author puts forward that the density of effective fractures controls the single-well output and the reservoirs of the Formation are fractured reservoirs. The conclusions achieved in this paper will provide a solid basis for the exploration evaluation, reserve upgrading and demonstration of development feasibility of oilfields in the future.

Key words: complex lithology, pored reservoir, structural fracture, effective fracture density, fractured reservoir, Malang Sag, Santanghu Basin