Sensitivity Analysis of Injection-Production Parameters for CO2 Huff-n-Puff Flooding and Storage in Tight Oil Reservoirs:A Case From Typical Tight Reservoirs of Chang 7 Member,Ordos Basin
CO2 huff-n-puff in tight oil reservoirs can enhance oil recovery and store CO2.The existing researches on CO2 huff-n-puff flooding and CO2 storage in tight oil reservoirs rarely take parameters related to CO2 storage capacity as evaluation indicators.Taking typical tight reservoirs in the seventh member of Yanchang formation(Chang 7 member)in the Ordos basin as an example,through numerical simula-tion,six injection-production parameters(huff-n-puff timing,injection rate,injection time,soaking time,production time and huff-n-puff cy-cle)and three evaluation indicators(oil exchange rate,CO2 retention coefficient,and flooding-storage synthesis coefficient)were selected.Using single-factor control variable method and multi-factor orthogonal experimental design,together with range analysis method,the sensi-tivities of the six injection-production parameters to three evaluation indicators were analyzed.The results suggest that in the CO2 flooding-dominant stage,it is recommended to set an injection time of 30-60 d,injection rate of 0.001 0-0.003 0 PV/d,and huff-n-puff timing of less than 0.5 a;in the CO2 storage-dominant stage,it is recommended to set a production time of 30-230 d,injection rate of 0.007 5-0.010 0 PV/d,and injection time of 145-180 d;and in the synergistic optimization stage of CO2 flooding and storage,it is recommended to set an injection time of 30-65 d,huff-n-puff timing of 6 months earlier,and soaking time of 10-20 d.
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