Experimental Study On Characteristics Of Oil And Water Seepage In Low Permeability And Tight Reservoir

Low permeability and tight reservoir has become the focus of oil and gas development.However,low permeability reservoir porosity and permeability of tight sandstone reservoir is very low,complex pore structure,strong heterogeneity,so continue to strengthen the research on the pore structure and seepage characteristics,has important practical significance to develop and improve the recovery rate of this kind of reservoir.In this paper,CJ low permeability tight reservoir as an example,based on the analysis of the reservoir rock properties and pore structure research,through the relevant laboratory core flow experiment,research the single-phase gas and water permeability of reservoir rock,seepage characteristics,characteristics of oil-water relative permeability,fracture seepage characteristics of artificial factors and its influence.The main results are as follows:1.Study area of reservoir permeability in 0.00102~1.84 mD,permeability is less than 0.1mD accounted for 68%,belong to low permeability reservoir,lithologic reservoir is mainly fine-grained lithic feldspathic sandstone;the reservoir permeability is low,mica and calcified clastic particles content is higher,the higher oil saturation of reservoir;clay mineral total average 9.78%,mainly chlorite(52.5%),(34.1%)illite / smectite,illite,illite mixed layer(12.8%)is 18.5%;the type of pore structure is complex,there are four main types,namely,intergranular pore-feldspar dissolution pass;feldspar dissolved pores,intergranular hole debris;-dissolved pore intergranular dissolved pores,carbonate dissolution pore type;extremely dense-intergranular microcracks-pore type,mainly in class II,III and IV class combinations,the reservoir rock faces this kind of total pore structure rate Generally less than 2%,the core permeability is less than 0.2*10-3m2,and the maximum pore throat radius of less than 0.75 m,micro pore throat and micro fracture development.2.In the study area,there is a great difference between the water phase and gas permeability of the low permeability and tight reservoir,and the biggest difference is that the water permeability of the reservoir is only 0.1% of that of the gas logging.Core cleaning gas measurement when the injection pressure,confining pressure,pressure sealing ring and other factors on the determination of dense reservoir permeability has important effect,before and after the dense core cleaning 0.1mD permeability permeability is less than the maximum rate of 41.3%;gas permeability greater than 0.2MPa injection pressure,gas permeability is relatively stable;stress sensitivity is strong,and the more dense core,the stronger the sensitivity of experimental conditions.3.Low permeability core has a strong self absorption capacity of study area,water flooding efficiency in 1.66%~22.7%;self absorption,surface active agent,artificial fracture has a great influence on the self absorption process,reverse imbibition than forward imbibition efficiency is high,the surfactant can make the permeability increased 3~ 6 times suction efficiency;artificial fracture of core cracks than the matrix core permeability increased by 39.5% the average absorption efficiency.4.Low permeability rock water displacing oil showed with the increase of water saturation in study areas,oil phase permeability decreases rapidly,water permeability to oil has increased very slowly,and the isoperm point is very low,the seepage zone is narrow,the residual oil water relative permeability is less than 0.1,and the low efficiency of water flooding,general less than 40%.5.Artificial cracks can greatly improve the permeability of tight reservoir rocks,the research of core and split area artificial fractures compared to before the gas permeability increased an average of 226.5 times,fracture permeability and pressure ring permeability decreased obviously,but it is far greater than the matrix permeability;crack surface roughness,core permeability after the closure of more cracks;core the single-phase formation water permeability is less than the permeability of bound water under the oil phase phenomenon.The research results of this paper provide a good theoretical basis for the development of low permeability and tight reservoir in CJ block,and it also has some guiding significance for the development of similar reservoirs.