Influence And Evaluation Of CO₂ Storage In C2380 Well Group Xishanyao Formation Reservoir In Cai9 Well Block Of Zhundong Area

The main reason for the increase in the concentration of CO₂in the global atmosphere is human activity,and the geological sequestration of CO₂is the separation of CO₂from concentrated emission sources,injected deep underground into a formation with suitable sealing conditions.The technology has the characteristics of large storage capacity,long storage time and mature technology,and it is the key link of carbon dioxide capture and storage technology.Geological storage of carbon dioxide needs a geological environment with large storage space,closed structure,security and stability in order to meet the storage requirements and prevent secondary disasters,therefore,there are strict technical conditions for geological storage.It is of practical significance for oil and gas production and environmental protection to carry out geological storage evaluation of oil wells.The main work of this paper:1)C2380 well area has obvious water drive effect in the early stage of water drive,and in the later stage,with the high-speed production of well area and the influence of reservoir Heterogeneity,micro-fracture and artificial fracture development,the water flooding and water channeling of oil well increase gradually,the water cut increases gradually,the daily oil production presents a decreasing trend,the stable production base of well area begins to deteriorate,and the annual oil production decline rate reaches 21.5%.2)The actual producing degree of oil layer drops,the problem of water flooding and water channeling is serious,a large number of oil wells with high water cut shut-off,the reservoir production continues to decline rapidly.Although infilling adjustment and multi-round comprehensive treatment have been carried out since 1999,the effect of treatment is not good.3)According to the statistics results of fluid production and water injection profile in C2380 well area,the average percentage of J₂x₁^2-2is 5.0%,the average percentage of J₂x₁^3-1is 19.5%,and the average percentage of J₂x₁^3-2is 32.4%J₂x₁⁴produced and absorbed 43.2%water on average.Up to now,C2380 well area has accumulated 45.85×10⁴tons of oil and 20.56?×10⁴tons of remaining reserves.4)The geological storage of CO₂in CAI9 well area in Zhundong area has the advantages of wide distribution area,good reservoir physical properties,suitable natural conditions,relatively high industrial concentration of CO₂emission and relatively high degree of oil and gas exploration,which is favorable for CO2 geological storage.It has favorable conditions for the integrated development of CO₂storage and oil displacement.5)Pilot test of CO₂ drive has been carried out in well C2380 of Western Hills kiln formation in well area Cai 9,and 1008T CO₂has been injected into the reservoir.The production performance of oil wells shows that the CO₂diffusion range is large and the gas absorption ability of low permeability reservoir is good.6)From the sealing property of caprock,there is no direct fault in C2380 well area.The caprock has good sealing property and has certain thickness and stable distribution.The average formation pressure is 21MPa,the main direction of channeling flow is 30o from nw to se and about 30 from NE TO S W.Reservoir fractures of the Western Hills kiln formation in well CAI9 area of Cainan Oilfield can be divided into natural fractures and artificial fractures,in which the natural fractures are mainly the result of tectonic stress and the artificial fractures are mainly the pressure-tension fractures.It is considered that C2380 well area is suitable for CO₂geological storage and has good oil displacement effect in the process of storage.Based on the analysis of this study,it is concluded that the reservoir of WesternHills Yao formation in CAI9 well,Karamay,Xinjiang,is a low permeability reservoir controlled by structure,fracture and lithofacies,and suitable for CO₂storage.CO₂flooding and storage experiments also show that CO2 diffusion range,low permeability reservoir gas absorption capacity is good,CO₂flooding test has achieved a certain oil-increasing effect.This study provides a practical case for the utilization and storage of CO₂in this area,and provides concrete data for the continued implementation of CO₂displacement and storage in this area.