Research On The Diagenesis Of The Upper 4th Member Of Xujiahe Formation In Centre-northwestern Of Sichuan Basin

There are Characteristics such as low permeability, low saturation of Xujiahe Formation in Centre-northwestern of Sichuan Basin. guided by the theory and method of sedimentology and diagensis of reservoir,and based on observation of microsection, electron microscope, X-ray diffraction and cathodelu-minescence,diagenesis of Xujiahe Formation are studied in depth. diagenesis comprehensive research believes that:The reservoir rock type of research area is mainly feldspar, the local development of lithic sandstone calcareous feldspar lithic snastone. the main reason of porous type reservoir formation is developmental compaction, pressure dissolving, cementation, dissolution and explaination diagenesis, chlorite ring edge cementation and dissolition is porous type reservoir formed the main reason,while crush real pressure dissolve role is dense of reservoir formation of an important controlling factors. According to Comprehensive reservoir characteristics and diagenetic performance, research area can be divided into seven diagenetic phase such as chlorite cementation diagenetic phase, crush real - dissolution diagenetic phase, crush real - weak dissolution diagenetic phase, calcium cementation diagenetic phase, crush real diagenetic phase, dissolution diagenetic and siliceous cementation diagenetic. Chlorite cementation diagenetic phase, crush real - dissolution diagenetic phase, dissolution is the most advantageous to the diagenesis phase diagenesis phase among them. The degree of Reservoir diagenetic evolution is higher, the overall of them in late diagenetic stage and the degree of anise field evolution is relative taller, which is mainly the late of rock B period, while chongxi region is the late of rock A period. The important controlling factors of the reservoir of diagenesis is sedimentary microfacies, rock components, diagenesis changes and buried depth.Reservoir space type is mainly surplus grain holes, various solution pores.The pore types of T3x4 have mainly surplus grain, dissolution hole, grains hole, overall,the reservoir property of T3x4 is good.Finally, through comprehensive consideration of the diagenesis, diagenesis phase and pore features, it was pointed out that the reservoir of research on the reservoir that's the vertical distribution of reservoir property in the lower of T3x4 better than the upper of T3x4 ;the plane distribution of reservoir property in the Chongxi area better than Bajiaochang area.