Abstract: Lucaogou formation of Malang sag in Santanghu basin is of variety and complexity of rock types, which were mainly resulted from multiple sources of sediments supply. The reservoir rocks are dominated by carbonate and tuff developed in the middle section of Lucaogou formation, and possess characteristics of zoned development of different lithology. Heidun zone is dominated by limestone and clastic rock; Mazhong zone by tuffite; Niuquanhu zone by sandy dolomite. The petrophysical property assumes low porosity and extra-low permeability. The reservoir space can be classified into three types, i.e., fracture, fracture-denudation pore and siliceous pore-crack. The porosity structure assumes medium-poor sorting, moderate flexure mini-pore and micro throat with poor pore-throat connectivity and micro fractures that play parts of connection, storage and percolation in the reservoir. The reservoir quality depends on how fracture developed in it. The diageneses such as buried denudation, fractured process and dolomitization are the major positive processes. The vertical fracture development and dis-tribution are related to in-situ lithology and bed thickness directly. It is shown that the most developed fractures are in the micrite and tufffite. The transversal fracture devlopment and distribution are controlled by in-situ structural location and fold amplitude or intension.

Key words: Santanghu basin, Permian, Lucaogou formation, reservoir, fracture, prediction