Study On The Chang 6₁ Tight Reservoir And The Oil-controlling Property Of The Reservoir In Foguyuan District Of Ordos Basin

The study of the Chang 6₁reservoir group in the Foguyuan area of the Qilicun Oilfield in the Ordos Basin is based on core description and logging data,combined with experimental methods such as casting thin-film observation,mercury intrusion,nuclear magnetic resonance,and whole-rock diffraction,from sedimentary facies,rock Research on the chemical characteris-tics,physical properties,pore structure and diagenetic evolution of the reservoir,and analyzed the control effect of deposition and reservoir conditions on hydrocarbon accumulation.The study concluded that the Chang 6₁sublayer in the study area belongs to the shallow water platform delta front subfacies deposits,mainly developing underwater distributary channels,underwater distributary bays and underwater natural dike microfacies.The sandstone of Chang 6₁reservoir is mainly gray-white fine-grained feldspar sandstone.The physical properties of the reservoir are generally poor.The porosity is between 2.47%?11.04%,the average porosity is 7.61%,and the permeability is between 0.01m D?7.66m D.The average permeability is 0.19m D,which belongs to low-porosity-low-permeability to tight sandstone reservoirs;the pore type is mainly secondary pores,and the pore structure is divided into three types.The causes of reservoir tightness are complex.The compaction destroys a large number of primary intergranular pores,which is the main factor leading to the densification of the reservoir in the study area;cementation is the second,and late cementation is the key factor for reservoir tightness;dissolution and Metasomatism improves the physical properties of the reservoir.The comprehensive evaluation model of reservoir is established on the basis of sedimentary reservoir research,comprehensively integrating sand body thickness,sedimentary microfacies,porosity,permeability and saturation,etc.,to obtain the comprehensive evaluation parameter F of the reservoir,which will change the Chang 6₁reservoir The quality ranges from good to difference into four categories:?,?,?and?.The F value of type I reservoir is greater than 0.75,the F value of type II reservoir is between 0.55?0.75,the F value of type III reservoir is between0.35?0.55,and the F value of type IV reservoir is less than 0.35.The initial monthly oil production of a single well is mainly affected by the sedimentary microfacies,sand body thickness,and reservoir physical properties;the"sweet spot"is predicted based on the distribution of favorable reservoirs in each small layer and combined with the actual production distribution.It is considered that I,II The superimposed area of similar reservoirs and the high value of oil production at the first month of a single well is a"sweet spot",which is expected to improve the exploration and development efficiency of oil reservoirs in this area.