Optimization And Evaluation Of Shale Oil CO₂ Huff And Puff Scheme

Shale reservoir has small porosity,low permeability and difficult development;The development of hydraulic fracturing enables the commercial development of shale reservoir,but its recovery is often less than 10%.It is necessary to effectively supplement formation energy to maintain production.After hydraulic fracturing,many gas channels will be formed.It is feasible to supplement energy and enhance oil recovery through CO₂huff and puff.This paper analyzes the geological and development characteristics of shale reservoir in Lucaogou Formation,determines the main controlling factors affecting productivity and the Hong Yuan model suitable for production decline analysis,and analyzes the oil increase mechanism of CO₂ huff and puff.Then,the numerical model of CO₂ huff and puff fracturing horizontal single well is established,and the influence of reservoir and construction parameters on the effect of huff and puff stimulation is analyzed.The factors affecting the recovery,formation pressure and recovery of horizontal wells are sorted by using grey correlation,orthogonal experiment and grey correlation analysis.Combined with orthogonal experiment and comprehensive analysis,the best construction scheme is determined.Finally,the economic feasibility of CO₂huff and puff scheme is determined.The analysis shows that reservoir factors such as reservoir thickness are positively correlated with oil production.The higher the parameter value of each reservoir,the better the effect of huff and puff oil increase,oil change and oil production;Injection rate,injection pressure and fluid production rate are positively correlated with oil production,while injection rate,soaking time and bottom hole flowing pressure are negatively correlated with oil production.The best construction scheme is:inject gas when the pressure is exhausted to 34 m Pa,the liquid production rate is 17 m³/day,the soaking time of each round is 20 days,the injection rate is 4000 m³/day,inject 1600tons of gas per round,and huff and puff for three to four rounds.Injection rate and fluid production rate are the main factors affecting recovery and oil change rate.Fluid production rate,injection rate and soaking time have a great impact on formation pressure.CO₂ huff and puff is more economically feasible than depletion mining.