Microscopic Pore Structure And Microscopic Remnant Oil Of Reservoir In Sabei Oil-water Transition Area

In order to research the microscopic pore structure,the mode of occerrences and distribution of microscopic remnant oil in different types of reservoirs of production tail,quantify and authenticate microscopic remnant oil,seek the main control factors,then give advice for improving oil recovery,this article based on the freezing preparation of thin sections and fluorescence,combined with pressured mercury analysis to research the Sabei transition area in Daqing Placantieline. The following results were obtained.The reservoirs physical properties of the Sabei transition area are good.High porosity and medium-high permeability reservoirs are the main types of this area.And the sedimentary facies here are delta plain facies and delta front subfacies.Pore throat radius are mainly distributed in 4-25 microns,which the 10 microns pore have the largest contribution to the permeability.With the Property classification standard and mercury intrusion parameters,the pore texture can be subdivided into 5 types.The I,Ⅱ,Ⅲ types which represent extra-high,high and medium permeability reservoirs are the main of this area.From I to Ⅴ types of reserviors,the pore throat radius decreases,the pore-throat ratio increase gradually,so the pore permeability gradually becomes poor.Research on the 18 samples of Well B2-60-FB271,the microscopic remnant oil of this area can be divided into 3 categories of 10 subclasses by its occurrence.The 3 categories are bound state,semi-bound state,free state. Bound state 3 categories:pore surface sheet film,adsorption particles,slit;semi-bound states of three types;coner-shaped,throat-shaped,pore center of precipitation:free state in 4 categories:cluster,state within the grain,adsorption-like between the grain,light mist.In the production tail,the free state microscopic remnant oil decrease and the bound state increase.Therefore,the oil saturation reduces.Different types of reservoirs have different types of microscopic remnant oil:cluster and state within the grain are the primary subclasses in the I reservoirs, adsorption-like particles is the main subclass in the Ⅱ, Ⅲ, Ⅳ reservoirs.The main control factors of this phenomenon are intraformational heterogeneity and interlayer heterogeneity.The more interlayers in the layer,the higher oil saturation it will be.Sedimentary micro facies,oil-bearing grade and degree of compaction are the secondary factors.Based on the research,measures for potential exploration of this area have been suggested.The remnant oil is enriched at the top of the channel sandbody,poor physical property of sandbody in the early development stage,the pore with good connectivity,the layer withrich oil and shallow.So we can reperforate at the top of the residual oil after polymer flood and the bottom of small channel sand.