Characteristics and main controlling factors of tight gas reservoirs in the second member of Triassic Xujiahe Formation,central Sichuan Basin
In order to clarify the characteristics,genesis and distribution of favorable reservoir in the second member of Xujiahe formation,comprehensively utilizing the thin sections,scanning electron microscopy,nuclear magnetic resonance,mercury injection and CT testing,the main controlling factors of tight gas reser-voirs were analysed.And based on the macro and micro parameters,classify the tight gas reservoirs quantitatively and distribute foe different kinds of reservoirs according to Q-cluster analysis.The results show that:(1)The reservoirs in the second member of Xujiahe formation in Hechuan area of central of Sichuan Basin are lithic feldspar sandstone and feldspar lithic sandstone,with an average porosity and permeability of 6.58％and 0.21 mD,which is typical ultra-low porosity and low permeability reservoir.The reservoir space in the second member of Xujiahe Formation is mainly residual intergranular pore and intragranular dissolved pore,secondly is inter-granular dissolved pore and fissure,the pore and throat radius range from 1.31 μm to 55 μm and 0.05 μm to 1.14 μm,classifying them as micrometer pores and millimeter-micrometer throats.(2)The granularity and shale content is controlled by the sedimentary,which is the basic for primary pore and its evaluate,while the pore distribution by compaction and cementation is 14.6％-20.1％and 9.8％-15.1％,which is the significance reason for the reser-voir densification.The dissolution and chlorite formed lots of intragranular dissolved pore,and protect some intergranular pore,which is helpful to the improve the tight reservoir into favorable reservoir.(3)Multiple parameters such as reservoir quality and pore structure was selected to divide the tight gas reservoirs into 4 kinds of different reservoirs,the reservoir quality and pore structure are different from each other in different kinds of reservoirs.The Ⅰ-type and Ⅱ-type reservoirs have a greater reservoir quality and pore structure,which is the main"sweet spot"in tight gas reservoirs and favorable development target in study area.The Ⅰ-type and Ⅱ-type reservoirs are development in H1,H3 well in the central and H125 well in the east,and they concentrated deve-lopment in the third and second layer in the upper of the second member of Xujiahe Formation.
tight gas reservoirsedimentationcompactioncementationsecondary dissolved poresselectityQ-mode clustingthe second member of Xujiahe FormationTriassiccentral of Sichuan Basin
万方数据
维普
