Investigation On Threshold Of Geological Parameters For Water Flooding Of The Ultra-low Permeability Reservoirs In Changyuan And Its Western Area

Since put into development from1982, with constantly innovating and developing ofoilfield flooding technique, oil reserves and annual oil production of peripheral Daqingoilfield increase year by year, and the annual oil production reaches500Mtpa. After theEleventh Five-Year Plan, targets evaluated and developed by peripheral Daqing oilfieldsharply worse off. Undeveloped proved reserves and residual controlled and prognosticreserves resourses of unproved areas are mainly ultra-low abundance and ultra-lowpermeability reservoirs, which distribute in Daqing Placanticline and its western areas.Comprehensively evaluating such ultra-low permeability reservoirs reveals the themicroscopic characteristics of pore texture and percolation mechanism. Optimizingdevelopment reservior and confirm limits of water flooding devepment technique aretechnical problems which are to be solved urgently in order to accelerate producing andupgrading reserves in such areas.In this dissertation, combining with mud-stoile casting, electric-microscope, constant ratemercury injection and nuclear magnetic resonance, we analyse the micro pore structurecharacter of ultra-low permeability reservoir, the shape of pore-throat, the size of the mineralgrains,and these factors can effect permeability; We can use constant rate mercury injection,the start-up pressure gradient test and the saturation of mobile fluid test, the filtrationcharacteristics of ultra-low permeability reservoir in Daqing Placanticline and the west ofthese area are researched; Through analyzing the influence of mainline throat radius,microcosmic heterogeneity characteristic parameters, movable fluids percentage, thresholdpressure gradient, oil viscosity and clay compositions on development effect oflow-permeability oilfields, low-permeability oilfields can be comprehensively evaluatedutilizing comprehensive sorting technique. Well patterns in Placanticline, western andsouthern areas of GuLong, southern area of QiJia and western area of Pu are researchedutilizing numerical simulation software of ultra-low permeability reservoirs which takenon-linear filtration into account.The main research results are as followed:1)Throat radius and distribution are the main factors that control reservoir permeability,The relationship between the average throat radius, the biggest throat radius, the averagepore-throat ratio, sorting coefficient and permeability are linear in semi-logarithmiccoordinates.2)The west of Daqing Placanticline, waiting for proven reserves, the minimum of limitflow about pore-throat, permeability and the minimum in water flooding about permeabilityhas been determined. Analysis think that limit flow about throat radius generally in0.2～0.5μm in each area, limit flow about permeability generally in0.1～0.3×10^-3μm², the limit in water flooding about permeability generally in0.7～0.9×10^-3μm². The strongest oil-waterflow are in the north area of Gulong, the second are in the south of Gulong, the west of Pu,the south of Qijia, the worst are in the west of Gulong and Daqing Placanticline. The reservoirabove2⁵×10^-3μm², the key about the difficult explore is driving pressure system can'teffective establish, microscopic heterogeneity is the key factors of affecting oilfielddevelopment.3) The results of evaluation about comprehensive classification of reservoir show that,the north of Gulong area belongs to classâ…  reservoir, own the best reservoir properties,most easy to use development; the west of Pu and the south of Gulong belongs to classIIreservoir, also is easy to use; the south of Qijia, the west of Gulong and Daqing Placanticlinebelongs to classâ…¢ reservoir, in order to effective use these areas, we need technologicalbreakthrough.4) The research of deploy well network shows that, Daqing Placanticline Fuyu reservoirchoose300m×100m well nets, the west of Gulong area choose400m×150m well nets, thesouth of Qijia choose500m×100m well nets, the south of Gulong area and the west of Puchoose500m×150m well nets.