Evaluation And Removal Method Of Retrograde Condensate Damage In The Let Naruoer Condensate Gas Reservoir

Zhalaroer condensate gas reservoir be a condensate gas reservoir with oil ring.During the development process,the formation pressure drops below dew point pressure,the ratio of producing gas to oil keeps rising,and the production of condensate oil drops rapidly.Whether the condensate gas reservoir has retrograde condensation or not,how much damage caused by retrograde condensation and related countermeasures are the urgent problems to be solved in the next development of the gas reservoir.Therefore,this paper establishes the comprehensive evaluation method of retrograde condensation injury,carries out the research on the degree of retrograde condensation injury and the method of relieving it,and puts forward the corresponding countermeasures.Based on single well production performance data and combined with geological conditions,this paper analyses the retrograde condensation characteristics and its impact on the performance of Zhalaroer condensate gas reservoir;synthesizes the previous experimental data of oil-gas phase state through the phase recovery theory,and fits with the actual production performance characteristics to define the fluid composition and properties of Zhalaroer condensate gas reservoir;uses the productivity equation considering condensate oil condensate,pressure.Force recovery well test interpretation,contamination skin factor and single well numerical simulation are used to evaluate comprehensively the damage degree of retrograde condensation process in Zhalaroer condensate gas reservoir,and to evaluate the effect of single well numerical simulation on relieving retrograde condensation damage by injecting different gas huff and puff and cyclic gas injection in well groups.Through the above researches,the following conclusions can be reached:(1)Gas reservoir production performance characteristics and decline law show that overall gas production and wellhead pressure decline slowly,condensate oil decline is higher than gas production,gas-oil ratio rises faster,reaching about 9000 m3/m3,which is about 2-3 times of the original,indicating that retrograde condensation loss is serious.(2)By phase recovery,it is determined that the gas well has undergone retrograde condensation at the beginning of production.At present,it is near the maximum retrograde condensation stage.The maximum retrograde condensation pressure is about 15-16 MPa,and the maximum amount of retrograde condensate is about 9-10%.(3)The productivity study considering retrograde condensation shows that the degree of damage caused by retrograde condensation increases with the increase or decrease of production pressure difference.Therefore,controlling the production pressure difference of single well and gas reservoir pressure preservation development play a positive role in reducing the damage caused by retrograde condensation.(4)The comprehensive analysis of the degree of retrograde condensation damage in Zhalaroer condensate gasreservoir shows that the oil productivity has great influence,the gas production has little influence,and the damage degree of single well is different.Generally,retrograde condensation belongs to low damage,less than 16%;the pollution radius is about 20-30 m,and there are differences among different wells.(5)The evaluation of removing retrograde condensation injury shows that the effect of CO2 huff and puff is better than that of dry gas and N2 huff and puff;the feasibility of removing retrograde condensation by hot nitrogen huff and puff;and the recovery degree of condensate oil can be improved by cyclic gas injection,and the influence of retrograde condensation pollution can be reduced,which has the effect of curing the root cause.