Coupling relationship of sedimentation-reservoir and comprehensive quantitative evaluation of braided river delta facies in Upper Karamay Formation, Hongshanzui area, northwestern margin of Junggar Basin

Core observation, thin section identification and data test were applied to analyzing the characteristics and quality-controlling factors of reservoirs in braided river delta. 5 parameters of porosity, ratio of sandbody, effective sandbody thickness, stratification coefficient of effective sandbody and matix content were chosen to evaluate the reservoir quantitatively, and gray correlation method was used to determine the weight coefficient and make critical point analysis to confirm the threshold value of various reservoirs. The results show that the lower delta plain is mainly classified as TypeⅠreservoir due to its good reservoir physical property and well-development of effective sandbody, while, in the upper delta plain, conglomerates of high matix content and poor physical property are assigned to typeⅡreservoir. The reservoir quality in delta front varies as its remarkable grain rhythm, with good quality in medium and coarse sandstone and poor quality in fine sandstone. And a limited development scale of the effective sandbody causes the delta front to be more likely recognized as TypeⅡand type Ⅲ reservoir. The results can provide reference for the quantitative evaluation of complex conglomerate reservoirs.