岩石相-沉积相双相耦合下优质储层分布特征OA

The exploration potential of the sixth segment of the Xujiahe Formation in the southern Sichuan Basin is enormous.This formation is mainly composed of delta front sediments,where the sand body thickness is large,and the heterogeneity is strong;however,the distribution characteristics of high-quality reservoirs in the basin are not yet known.By utilizing data such as core samples,well logging,and analytical testing,sedimentary microfacies and rock facies are classified to determine favorable rock facies types for high-quality reservoirs.A well-logging prediction model is established,which is combined with macroscopic distribution and evolution laws of sedimentary facies to analyze the planar distribution characteristics of high-quality reservoirs in the sixth segment of the Xujiahe Formation.The research results indicate that:(1)The rock facies types in the sixth segment are mainly inclined bedding coarse-grained feldspar lithic sandstone,blocky bedding coarse-grained feldspar lithic sandstone,inclined bedding medium grained feldspar lithic sandstone,inclined bedding coarse-grained lithic sandstone,parallel bedding fine-grained lithic sandstone,inclined bedding medium grained lithic sandstone,inclined bedding fine-grained lithic sandstone,and sand ripple bedding extremely fine-grained lithic sandstone.(2)The sedimentary microfacies can be subdivided into underwater distributary channels,river mouth dams,sheet sand,and shallow lake mud.Based on their spatial distribution characteristics,the sixth segment underwent the complete process of lake invasion and retreat.(3)The rock types are mainly feldspar lithic sandstone and lithic sandstone.For tight reservoirs with ultralow porosity and permeability,the reservoir space mainly consists of residual intergranular pores,feldspar dissolution pores,intergranular dissolution pores,and microcracks.(4)Based on reservoir characteristics and oil testing results,four favorable rock facies were selected as high-quality reservoirs.Based on the spatial distribution of sedimentary microfacies,it is believed that the distribution range of high-quality reservoirs is roughly similar to that of underwater distributary channels.The plane thickness gradually decreases from the south to the northwest,and the lower longitudinal part of the lower subsegment of the sixth segment of the Xujiahe Formation is better than the upper subsegment.It is found that the sedimentary facies type controls the spatial distribution of high-quality reservoirs,while the rock facies type determines the spatial differences in storage capacity within high-quality reservoirs.The use of biphasic coupling can accurately predict the spatial distribution characteristics of high-quality reservoirs,providing a basis for the subsequent prediction of terrestrial tight sandstone natural gas reservoirs.