| Y is At the south of Ordos Basin,the permeability of tight sandstone gas reservoirs is 0.00272~0.266×10-3?m2,the porosity is 0.476~1.4%,the damage of water lock is extremely serious during the development of gas reservoir,the production is very low after fracturing.At the center of H,the permeability of tight oil reservoirs is from 0.0296 to 1.270×10-3?m2,the porosity is from 0.532% to 15.975%,there are water locking damage and improve water flooding recovery problems in the development process.Because of the tiny pore throat and the highly capillary force in tight reservoir,the phenomenon of imbibition can not be ignored in the development of dense reservoir.Paper wicking theory,the use of mercury,scanning electron microscopy and thin,spontaneous imbibition and other physical simulation technology,systematic study of the Y and H tight gas reservoirs dense microscopic pore structure characteristics,In this paper,we study the phenomenon of imbibition and the influence of the two tight reservoirs.The conclusions and understanding is following.(1)There are four kinds of typical type curve in the the phenomenon of imbibition and the process are complicated.in the study area the rate of imbibition and the amount of imbibition are relatively large,the final amount of wicking 36.5%~94.1%,averaging 63.7%.(2)The permeability of tight gas reservoirs have a big impact on imbibition,the higher the permeability,the lower the amount of water absorption and tight gas and the longer the ultimate self-priming time,strong heterogeneity of reservoir rock,small pore throat,strong heterogeneity of reservoir rock,there are large imbibition and high speed in micro-fracture cores.on the other hand,there are little of imbibition in clay minerals and high content of mixed layer illite.In the experimental process the imbibition in side closed core are short of fully open core,the core adding surfactants have low speed imbibing and low imbibition.(3)After imbibiting the core Water will invade at a faster rate from the end of the invasion gradually to the entire core,finally water in the core will show a uniform distribution,the presence of initial water saturation cores,there is a certain influence on water in diffusion,when the initial water saturation cores average to 5.1%,the diffusion of water have slow down to half of it.inhalation formation water in tight gas reservoirs have seriously affect on the permeability core in the study area,however,core permeability have significant recovery after the diffusion of water;but the initial water saturation core is relatively slow on permeability recovery rate,the ability to invade the diffusion of water is highly relate to the reservoir rock pore structure,the main solution pore pore structure + slit combination in the study area of reservoir rock,a combination of microporous + slit type,lithology,structure and interstitial material composition and reservoir rocks,occurrence is closely related.(4)Tight oil reservoir core in study area have good water infiltration capacity,water permeability reservoir displacement efficiency in the distribution of 9.84%~79.9%,so the research on seepage water flooding to some extent can improve the reservoir waterflooding.but when permeability less than 0.05 mD,seepage water oil displacement efficiency than the relative permeability decreased by more than 10%.(5)The study area are tight reservoir rock wettability neutral-lipophilic,has a certain effect on the imbibiting reservoir,reservoir rock containing more lipophilic have a certain relationship to chlorite,the main in district storage space for infiltration intergranular pores,solution pore,porous,the main types of pore structure are combination of the pores(intergranular holes,corrosion holes and pores)+ microcracks combination type,the combination of rock pore are simple,storage layer of rock pore throat tiny pore throat radius mainly in the 0.01-1?m range in the study area,Capillary force stronger,are the main reason to large water permeability reservoir and high-absorbent speed. |
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