Study On Water Absorption Characteristics Of Reservoirs In Chaoyanggou Oilfield

Chaoyanggou Oilfield is a low-permeability reservoir with small pores and throat radius,complex pore structure,low reservoir permeability,and strong lo ngitudinal and planar heterogeneity.Injection and production are common in th e development process.The ratio is high,the reservoir has insufficient water a bsorption capacity,and it is difficult to establish an effective driving system be tween oil and water wells.These phenomena are contrary to the principle of material balance.Therefore,this paper uses physical simulation methods to con duct an in-depth study on the cause of high injection-production ratio in Chaoy anggou To clarify the characteristics of reservoir water absorption in Chaoya ng gou Oilfield,establish a new mathematical model of formation water absorption,and provide scientific and effective design basis and theoretical basis for wate rflooding development in Chaoyanggou Oilfield.Mainly achieved the following results and understanding:First of all,the research and analysis of the logging data of the inspection wells and the comprehensive histogram of the oil layer washing status of vari ous blocks in the Chaoyanggou Oilfield are given.The longitudinal lithology d istribution characteristics and thickness ratios of the first,second and third bloc ks are given,and Chaoyang is determined.There are 9 types of lithology in T ype 1 and Type 2 blocks of Gou Oilfield,14 types of lithology in Type 3 blo cks,and 5 types of main lithologies in Type 1,2 and 3 blocks,which are pur e mudstone and sand.Mudstone,argillaceous siltstone,siltstone and reservoir s andstone;according to the lithology distribution characteristics of various blocks,refer to the main rocks in the vertical direction of the F21 layer of the first type block,F173 layer of the second type block and F112 layer of the third t ype block According to the distribution ratio,3 composite lithology models of various blocks without artificial cracks and 3 composite lithology models of va rious blocks with artificial cracks were produced.Secondly,an experimental study on the characteristics of single lithologic water-holding capacity was carried out.The characteristics of pure mudstone,s and-bearing mudstone and transitional lithologic water-holding capacity were stu died separately.Characteristic of water-holding capacity: Pure mudstone basically does not have permeability,mainly relying on clay hydration to absorb water,the water-holding capacity curve changes in a "factory" shape,and the saturati on water-holding coefficient increases with the increase of pressure at the imm ersion end.The increase becomes smaller;it decreases with the increase of the distance from the flooding end to the center of the rock sample;based on th e experimental results,a calculation formula between the pure mudstone water capacity and the above parameters is established.Sand-bearing mudstone has a certain permeability,and the water-holding characteristics are between pure mud stone and transitional lithology.The fluid in the pores has a pressure conductio n phenomenon,and the pressure at the core end gradually increases.The water-holding characteristics of the transitional lithology are consistent with the com pression characteristics of the fluid.According to the experimental results of cl osed core samples,there are some hydrocarbon gases in the transitional litholo gical pores,and the elastic compression coefficient is significantly higher than t hat of the liquid.Then,carrying out experimental research on water absorption characteristics of various block composite lithology models,fully simulating the actual condit ions of reservoir development;firstly,we analyzed and analyzed the injection-p roduction ratio and the pressure variation characteristics of different parts of th e model,of which the first,second and third areas In the early stage of floodi ng with block composite lithology model(without fractures),the reservoir and transitional lithology pressure gradually increased,and the amplitude gradually t ended to be gentle with the increase of time;the pressure of sand-bearing mud stone and pure mudstone showed a rising trend.,But the range is slow;it ind icates that the transitional lithology,sand-bearing mudstone,and mudstone are a ll water-absorbing,and the composite lithology model(with fractures)of the fir st,second,and third types of blocks has different lithology than the composite lithology model of the fractureless reservoir The initial pressure rises quickly,but the overall pressure change trend is consistent with the compound lithology model of the fracture-free reservoir.Subsequently,according to the change rel ationship between water absorption and pressure of each lithological water in a single water holding feature,the water absorption in the composite model of various blocks is split,and the water absorption and water absorption ratio of various lithologies are determined.The water absorption of the compound lithol ogy model(without fractures)of the first,second,and third types of blocks allshowed a gradual increase in the beginning,and finally reached a steady tren d;the injection-production ratio basically reached equilibrium by 72 hours after the displacement,and the first,second,and third Reservoir,transitional litholo gy,sand-bearing mudstone and pure mudstone in the reservoir-like composite m odel(without fractures)account for 0.63;0.28;0.05;0.04,0.52;0.30;0.11;0.07,0.48;0.32;0.12;0.08,and the change trend of water absorption of compo und lithology model(with fractures)in the first,second,and third blocks is co nsistent with the non-fracture compound lithology model;the injection-productio n ratio is basically balanced by 72 hours after the displacement.The proportio ns of water absorption of reservoir,transitional lithology,sand-bearing mudstone and pure mudstone in the three types of reservoir composite models(with fra ctures)are 0.55;0.33;0.07;0.04,0.49;0.31;0.12;0.08,0.43;0.30 0.14;0.12.Finally,based on the experimental results of single lithologic water-holding characteristics and composite lithological model water absorption characteristics,a mathematical model of formation water absorption considering reservoir,tran sitional lithology and mudstone was established,and the mathematical model w as solved by combining the difference method and the material balance method Analytical solutions for the average pressure of the reservoir water well contr ol area,reservoir oil well control area,transitional lithology and mudstone are given respectively.The model is verified and the mine case calculation is perfo rmed using experimental data,numerical simulation software and actual field da ta.The accuracy is within 3.5%.