关键词: 四川盆地, 上三叠统, 须家河组, 沉积微相, 成岩作用, 石英溶蚀作用, 储层效应, 分布模式

Abstract:

As the main reservoir of natural gas resources, the sandstone reservoirs of Xujiahe Formation in the Upper Triassic of Sichuan Basin were influenced by many geological factors. The sedimentation controls the spatial distribution of reservoir framework and affects the events and intensity of the subsequential diagenesis. During burial period, diagenesis is the key factor for reservoir evolution, because it influences both the reservoir spaces and porosity structures, and finally decides the present reservoir property and their distribution law. The numerable measured data of porosity and permeability show that the reservoir property gets better gradually from top to bottom in Xujiahe Formation of Hebaochang Block in the south part of the Central Sichuan Basin. The lowest sandstone in SectionⅡ of Xujiahe Formation keeps the better quality than those distributed in Section Ⅳ and Ⅵ of Xujiahe Formation. Pervasive occurrence of the secondary pores produced by quartz dissolution is the main reason for the better quality of Xujiahe sandstones. In combination with the geological background of the study area, six types of depositional-diagenetic coupling complex in the Triassic clastic reservoirs were recognized according to the superimposition of diagenetic events of different sedimentary microfacies and the response of reservoir. The detailed information of the reservoir parameters for these coupling complexes was described. The constructive and destructive coupling types of reservoir parameters were subdivided. A distribution model of depositional-diagenetic coupling complex in the studied area was established.

Key words: Sichuan Basin, Upper Triassic, Xujiahe Formation, sedimentary microfacies, diagenesis, quartz dissolution, reservoir effect, distribution mode