Enhanced Recovery in Middle and Late Stages of Depletion Development of Condensate Gas Reservoirs With Oil Ring
The depletion development of Y5 condensate gas reservoir in the Tarim basin encounters the challenges such as rapid decline in both reservoir pressure and well productivity,gradual decrease in produced gas-oil ratio,increase in condensate oil density and viscosity,and fast downgrading of development performance.Combining performance analysis and reservoir fluid component evaluation,the Y5 con-densate gas reservoir was redefined as a layered condensate gas reservoir with oil ring and edge water and the thickness of the oil ring was determined through numerical simulation.To improve the development performance and enhance the condensate oil/gas recovery,a system-atic investigation was conducted on the mechanism of enhanced recovery in the middle and late stages of depletion development of the con-densate gas reservoir with oil ring.It is found that optimizing the well pattern and implementing cyclic gas injection can significantly im-prove oil and gas recovery.Gravity-assisted gas drive is recommended,with CO2 being the optimal injection medium,followed by reservoir gas.Based on reservoir type and enhanced recovery mechanism,a scheme of cyclic gas injection for enhancing the recovery of Y5 conden-sate gas reservoir was developed,with an expected oil recovery 29.96%higher than that of depletion development alone.Under this scheme,a cumulative gas volume of 0.19×108 m3 was injected,the reservoir pressure restored by 4.31 MPa,and the well productivity in-creased by 3.09 times compared to that before the scheme was implemented.The research results provide valuable reference for enhancing recovery in the middle and late development stages of similar reservoirs.
Tarim basincondensate gas reservoiroil ringmiddle-late development stagecyclic gas injectionEORdevelopment mecha-nismgravity-assisted gas drive
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