Analyzing vertical lift performance in a complex gas lift well gometry

Abstract

This study mainly investigates the vertical lift performance in a complex gas lift well geometry. Prosper is used to do gas lift design. OLGA is used to analyze the dynamic well behavior based on the gas lift design from Prosper. The study is started by analyzing the effect of well geometry by comparing the J-shaped well to the horizontal well with and without gas lift. It is continued by analyzing the effect of gas lift to well performance and startup behavior of the J-shaped well. The sensitivity of reservoir pressure, productivity index, water cut and surface casing pressure is covered in this study. In the last part of this study, transient reservoir behavior is covered to optimize classic gas lift design. Steady state and dynamic simulations are performed to fulfill the objectives of this study.

The J-shaped well demonstrates unfavorable behavior compared to horizontal well. The J-shaped well is prone to slugging behavior. To properly evaluate the possibility of producing a well without the aid of gas lift, it is recommended to simulate the segregation during shut in and following by startup/unloading sequence. Otherwise, the steady state simulation result can be misleading because it does not model the dynamic behavior during unloading. Gas lift can extend the lifetime of well with strong transient reservoir behavior. Gas lift can increase the regularity wells with cyclic behavior. In terms of stability, gas lift well can mitigate the instability. However, a large amount of gas lift is required to stabilize the flow. Steady state simulation is currently the standard technique utilized to do classical gas lift design. Dynamic/transient simulation is recommended for validation purposes of gas lift design intended for wells with complex well geometry. Modeling should be implemented in the future to engineer/design gas lift solution for wells with complex well geometry.