Study On Reservoir Physical Properties And Seepage Characteristics Of A Tight Reservoir In Daqing

Tight reservoirs refer to its upper limit permeability is 1mD or 3mD,and the lithology is mainly sandstone,shale and carbonate.China's vast territory and abundant oil resources have great potential,tight reservoirs mainly distributed in the Cretaceous sandstones in the northern Songliao Basin,the Permian cloud rocks in the Zhungeer Basin,the Shahejie Huyan carbonate rocks in the Bohai Bay Basin,and the Yandu Formation in the Ordos Basin.Tight sandstone,Cretaceous marl in Jiuquan Basin,Jurassic in Sichuan Basin,etc.In 2011,Daqing Oilfield began to explore effective exploration and development approaches for tight oil.Compared with general reservoirs,tight reservoirs are characterized by poor physical properties,strong inter-layer heterogeneity,and complex oil-water relationships.They are also characterized by no natural production capacity.In this paper,the natural core of the Daqing G block reservoir is selected.According to porosity and permeability experiment,clay mineral analysis,nuclear magnetic resonance,scanning electron microscopy and single-phase water flooding experiments,oil-water seepage experiments,the reservoir physical properties and seepage characteristics are systematically analyzed,and get the following conclusions and understanding:(1)The reservoir porosity of Daqing G block is concentrated at 7%~13%,the average porosity is 11.55%,the minimum permeability of core is 0.016 mD,and the maximum permeability is 0.277 mD.The average permeability is 0.09 mD,and the permeability is low,which belongs to a tight reservoir.(2)The poresin this block are bad and the connectivity is poor.The average amount of clay minerals is 13%,mainly chlorite,illite and illite/smectite interlayer.The reservoir is dominated by submicron pores,the pore radius is concentrated between 0.01-0.1?m,accounting for 89.16%,and larger than 1?m account for 10.7%,submicron pores are the main reservoir space and flow channel for oil and gas in this block.(3)The fluid in the G block reservoir has a high degree of fluid binding and poor mobility.The single-phase water seepage characteristics are consistent with the new nonlinear seepage model which based on the boundary layer theory.(4)Due to the extremely low permeability of the block,the oil-water seepage is mostly infiltration.Under higher displacement pressure,the crack will expand and the seepage capacity increase.(5)During the oil-water seepage process,after the water saturation exceeds 33%,the water begins to appear,when the water saturation is greater than 61%,the permeability of oil is 0,then the core only produces water.