In this paper

reservoir characteristics

sedimentation and diagenesis of the Xujiahe Formation in the central and western parts of the Sichuan Basin are studied through microscopy observation of cast thin sections

analysis of physical properties

scanning electron microscope and X-diffraction.The results show that pores in the Xujiahe Formation of the study area are mainly residual primary intergranular pores and intragranular dissolution pores.With an average porosity of 5.83% and average permeability of 0.283×10

-3

μm

2

the reservoirs are classified as low-porosity and low-permeability reservoirs.Sedimentation and diagenesis are the main factors controlling the development of reservoirs.Favorable facies belts for the development of reservoirs are river mouth bar and underwater distributary channel microfacies in the delta front.Compaction is the main influencing factor which led to the loss of porosity in the reservoirs.Early rim cementation of chlorites helped to protect the residual primary intergranular pores

and dissolution contributed the most to the development of reservoirs.