Reservoir characterization and controlling factors of Ordovician weathering crust reservoir in Yubei area,Tarim basin

To analyze Ordovician weathered crust reservoir in Yubei area of Tarim basin,based on logging data,cores and microscope observation,studies of weathering crust reservoir characteristic,reservoir distribution and reservoir controlling factors have been carried out.It is considered that weathering crust developed in middle Caledonian and early Hercynian.Yingshan formation is the best developed weathering crust formation.Reservoir distributed vertically in high-angle solution fissures,half filling dissolution pores,interparticle dissolution pores and intercrystalline solution pores of horizontal undercurrent belts and half filling high-angle solution fissures and small and medium-sized dissolution pores of vertical vadose belts.Favorable reservoirs are mainly distributed in karst highland and karst slope.Large cave collapse breccias,karst cave,dissolved pores and solution fissures are the main reservoir space.Fissures in Yubei area,which are connected with solution pores,are so well developed that they can enhance penetrating quality of carbonate reservoir.Development of long-term exposure and erosion of formation caused by Caledonian-Hercynian tectonic movement,fracture movement and fracture development are the important controlling factors of the weathering crust reservoir formation.Yingshan formation carbonatite of the eastern fault is the favorable exploration area.