Longitudinal Injection-production Control Technology Of CO₂ Flooding In Glutenite Reservoir

Glutenite reservoirs have the characteristics of long oil-bearing well interval,large difference in oil layer thickness,complex interlayer connections,and serious heterogeneity.During the development of CO₂flooding,problems such as gas channeling and gas capping are prone to occur,resulting in a low longitudinal sweep coefficient,which has become a key issue restricting the development of CO₂flooding.Therefore,studying the injection-production control technology of CO₂flooding and increasing the longitudinal sweep efficiency of CO₂flooding are of great significance for improving the development effect of CO₂flooding in glutenite reservoirs.Based on the characteristics of the glutenite reservoir in Block Y of Shengli Oilfield,this paper establishes CO₂ flooding component numerical simulation model in glutenite reservoirs,and proposes three longitudinal combined gas injection modes:interval combination,permeability combination,and effective thickness combination.Establish the division method of combining optimization theory and numerical simulation,the CO₂ flooding injection-production method and injection-production parameters were optimized,and the Y block development plan was designed.The research results show that:（1）The optimization method can accurately achieve the division of intervals,and the optimal interval division plan of Y block is 3 stages;（2）The optimal method of interval combination gas injection mode is from bottom to up.This way can fully weaken the influence of gas cover,and the overall displacement effect will be more equilibrium;（3）The optimal method of thickness combination gas injection mode is first thin alternating thick,and the optimal method of permeability combination is first low permeability alternating high permeability;（4）Top injection and bottom production is adopted for single block thick layer,thin layer injection and thick layer production is adopted for the connected complex layers in the middle fan,and high injection and low production is adopted for large dip angle layers;（5）Reasonable pressure level for CO₂ flooding is 1 MMP,the gas injection rate is 0.4 HCPV,and the oil production rate is 2%-3%;（6）The optimal development plan of Y block is:adopt five-point well pattern,interval combination gas injection mode of from bottom to up,horizontal pressure 1 MMP,total gas injection rate 0.4 HCPV,the gas injection volume of the interval is distributed according to the total permeability;（7）The 30-year recovery rate of CO₂ flooding combined gas injection in block Y is 34.91%,which is 14.25%higher than water flooding and 7.23%higher than co-injection and co-production.