Research On Evolution Of Diagenesis And Its Control On Tight Oil Accumulation Of Chang 6 Rreservoir In Wuqi Area, Ordos Basin

The Chang 6 reservoir in the Wuqi area,Ordos Basin contains extremely rich oil and gas reserves,but at present,the study on the formation and evolution of the reservoir and its control of reservoir formation is still relatively weak,and the progress in the exploration of dense oil is slow.In this paper,the geological characteristics of the 6 reservoir,the evolution of the pore formation and the control of the reservoir formation have been studied in the light of the experimental data of thin film observation,mercury pressure testing and the temperature measurement of the inclusions.The study shows that the 6 sand bodies in the Wuqi area are mostly the two types of feldspar and lithic feldspar,and the main composition of the reservoir sand body fillings includes the chlorite and the iron calcite cementation.In the study area,the average porosity is 10.15%,and the average permeability is 0.467 mD.According to the distribution characteristics,the whole reservoir belongs to low porosity and ultra-low permeability reservoirs.The main types of pore development are residual primary intergranular pores and secondary intergranular dissolved pores.The diagenesis of reservoirs is mainly compaction,cementation and dissolution,and the diagenetic stage is in the middle diagenetic A stage.The homogenization temperature of inclusions indicates that the hydrocarbon filling time of Chang 6 reservoir is about 130 Ma.Through the analysis of the force of oil and gas,it is concluded that the porosity of the tight and critical physical condition is 12.22%,the permeability is 0.38 mD,and the tight time of the reservoir is about 170 Ma.Therefore,it is determined that the reservoir has became dense before formed.