Numerical Simulation Of CO₂ Huff-and-Puff During Fracturing And After Fracturing In E Nan Shale Oil Reservoirs

China has abundant shale oil reserves,but the low porosity and low permeability characteristics of shale oil reservoirs lead to their elastic recovery and recovery is still very low,and it is urgent to increase the recovery of shale oil.The new technology of CO₂ fracturing and CO₂ huff-and-puff are measures to effectively improve oil recovery in shale oil reservoirs.Through numerical simulation of CO₂ huff-and-puff during fracturing and after fracturing in E Nan shale oil reservoirs,this paper optimize CO₂huff-and-puff parameters,fractures parameters and estimate the impact of CO₂huff-and-puff on recovery.In this paper,first,the oil composition parameters are fitted according to the oil composition experiment,and the single-well numerical simulation model is established based on shale formation parameters and reservoir physical property parameters of E Nan shale oil reservoirs.Then it uses single-factor analysis to study the influence of reservoir parameters,fractures parameters and CO₂ huff-and-puff parameters on CO₂huff-and-puff of fractured horizontal well;and then use orthogonal test design methods to optimize the huff-and-puff parameters.Finally,a set of schemes for CO₂huff-and-puff during fracture and after fracturing in E Nan shale oil reservoirs were proposed,and the effect of stimulation was analyzed..The results show:taking into account the four indexes of cumulative oil production,cumulative gas production,CO₂ oil exchange rate and CO₂ return rate within one year.The optimal combination was obtained by fuzzy comprehensive evaluation,which are fracture conductivity of 10um²·cm and flowing bottomhole pressure of 10MPa,CO₂injection volume of 640m³ per fracture during fracturing,CO₂injection rate during fracturing of 2m³/min,soaking time of 11 days,fracture half length of 150m,the number of fractures of 25.Under the optimal combination of parameters,the cumulative oil production is 3907.32m³,the cumulative gas production is 778040.22m³,CO₂ The return rate is 72.58%and the oil change rate is 0.89m³·m^-3.