Characteristics and quantitative study on gas breakthrough in developing Yaha-2 condensate gas reservoir in Tarim Basin, China

Abstract

In order to keep the formation pressure be larger than the dew-point pressure to decrease the loss of condensate oil, cyclic gas injection has been widely applied to develop condensate gas reservoir. However, because the heterogeneity and the density difference between gas and liquid are significant, gas breakthrough appears during cyclic gas injection, which apparently impacts the development effects. The gas breakthrough characteristics are affected by many factors, such as geological features, gas reservoir properties, fluid properties, perforation relations between injectors and producers, and operation parameters. In order to clearly understand the gas breakthrough characteristics and the sensitivity to the parameters, Yaha-2 condensate gas reservoir in Tarim Basin was taken as an example. First, the gas breakthrough characteristic of different perforation relations by injecting natural gas was studied, and the optimal relation was achieved by comparing the sweep efficiency. Then, the designs of orthogonal experiments method were employed to study the sensitivity of gas breakthrough to different parameters. Meanwhile, the characteristic parameters, such as gas breakthrough time, dimensionless gas breakthrough time, and sweep volume, were calculated and the prediction models were achieved. Finally, the prediction models were applied to calculate the gas breakthrough time and sweep volume in Yaha-2 condensate gas reservoir in Tarim Basin. The reliability of the model was verified at the same time. Please see the Appendix for the graphical representation of the abstract.