Abstract: This paper proved that grain size composition of pluvial fan conglomerate has self-similar fractal structure by applying fractal theory.The calculations showed that fractal dimention number of conglomerate is bigger than that of sandstone, and conglomerates with different origins have different fractal dimension numbers.Based on the application of fractal dimension number of grain size composition in sedimentary environment interpretation and reservoir evaluation and case study of conglomerate reservoi r in Karamay oilfileld, it is indicated that the fractal dimension number of grain size composition can reflect the evolution of sedimentary environment, and also establishes linear relationship with sorting coefficient and permeability of rock.

Key words: Junggar basin, Karamay oilfield, Conglomerate, Grain size, Fractal, Principle, Application