| The DZ block is a low permeability reservoir,poor reservoir property,low productivity,at present the block is developed by water flooding,due to the low permeability and the presence of micro cracks,oil production decline fast,injected water along the direction of the micro crack onrush.The production wells in the fracture direction are too early to see water,and the lateral production wells are slightly affected by water flooding,and the recovery rate is low.The urgent need to find a suitable for low permeability reservoir EOR method.According to the method of carbon dioxide huff and puff in low permeability reservoir,the variable weight fuzzy analytic hierarchy process(AHP)is applied to the selection of low carbon dioxide huff and puff location.In consideration of the reservoir thickness,residual oil saturation,oil moisture content,permeability and porosity 5 parameters under the condition of weight distribution parameters in the carbon dioxide injection were determined,including reservoir thickness and permeability affected most significantly,the oil saturation and the influence of water content of minimum porosity effect.The well selection method solves the problem that the lack of some parameters in the selection of low carbon dioxide huff and puff in the low permeability reservoir leads to unreasonable results of well selection,which makes the well selection result more accurate.In a preferred location on the basis of the reservoir engineering method according to the characteristics of relative permeability of oil and gas and oil,oil production index and the index below the bottom suction,fracture pressure conditions,designed every wells of different injection parameters under pressure,the injection rate is 7.87?140.65 t/d injection 78.84?114.37t,soak time is 38?55 d,the throughput for the period from 1 to 3.By using production data and geological data,the use of Petrel through structure modeling,data analysis,attribute modeling geological model is established in this area,reserves fitting precision reached the requirements for simulation and finally got coarse mesh size of the geological model of 35m × 35m.According to the method of carbon dioxide huff and puff in low permeability reservoir,the variable weight fuzzy analytic hierarchy process(AHP)is applied to the selection of low carbon dioxide huff and puff location.In consideration of the reservoir thickness,residual oil saturation,water content,penneability and porosity 5 parameters,the weight distribution of each parameter in the carbon dioxide injection were determined,including reservoir thickness and penneability affected most significantly,the o oil saturation and water cut are the second,porosity is the least.The well selection method solves the problem that the lack of some parameters in the selection of low carbon dioxide huff and puff in the low permeability reservoir leads to unreasonable results of well selection,which makes the well selection result more accurate.According to the selected location,using reservoir engineering method,according to the characteristics of the relative permeability curve of oil and gas and oil production index,designed every wells of different injection parameters under the bottom fracture pressure,the injection rate is 34.78?66.94 t/d,the injection volume was 78.84?114.37t and the soak time is 38?55 d,the cycle period from 1 to 3.According to the well location,the geological model is introduced into Eclipse.The PVTi model was used to simulate the deviding of the pseudo components,the fitting of the saturation pressure and the single degassing experiment,the fitting of the differential profit experiment and the expansion of the gas injection experiment.According to the production data,the production history matching of the whole area and single well were carried out respectively,after that,the parameters of the injection rate,injection volume,the soaking time and the number of the huff and puff period of each well are optimized.83-54 wells in the 2 cycle throughput,average daily oil production increased from 0.60 m~3/d to 1.32m~3/d,the cumulative increase of oil 517.54m~3,the gas to oil exchange ratio of 2.07t/t;83-56 wells in the 2 cycle throughput,average daily oil increased from 0.36 to 1.93m~3/d,the cumulative increase of oil 414.07m~3,the gas to oil exchange ratio of 1.72t/t 84-521 in 2 wells;a soaking period,the average daily oil increased from 0.46 to 0.97m~3/d,the cumulative increase of oil 363.94m~3,the gas to oil exchange ratio of 1.53t/t;85-53 wells in the 1 cycle throughput,average daily oil increased from 0.43 to 1.08m~3/d,the cumulative increase of oil 233.12m~3,the gas to oil exchange ratio of 2.66t/t;85-55 wells in the 1 cycle throughput,average oil production increased from 0.37 to 0.90m~3/d,the cumulative increase of oil 191.59m~3,the gas to oil exchange ratio of 1.82t/t,indicating good stimulation effect.Finally,the change of crude oil volume,viscosity,interfacial tension,the change of light components in crude oil and the mechanism of oil recovery by carbon dioxide extraction are analyzed. |
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