Dynamic Wellbore Modeling for Multilayered Gas Condensate Wells with Water Vapor Content Using Olga: A Case Study in Camisea Field.

Abstract

This paper discusses the historical evolution and future performance of wellbore dynamics in a multilayered gas condensate well (100 MMSCFD) in the Camisea Field - Peru. The analysis included the modeling of water vapor content produced within the gas condensate stream and its multiphase behavior and interaction with other fluids inside the borehole through the reservoir depletion under commingled production. The goal of this study is to quantify the impact of the wellbore dynamics in well deliverability and the effective recovery of hydrocarbons for each individual layer, and propose actions to achieve an optimum production scheme. The approach is based on the modeling and matching of dynamic behavior of the wellbore and individual layers with the observed data during 9 years. For this purpose a dynamic wellbore model was built using OLGA. The inputs to the model are: 1) the properties for each productive layer characterized using multirate test combined with PLT logs to get the individual IPR's; 2) the model of the reservoir fluid to properly represent the retrograde condensation and the behavior of water in the vapor phase; and 3) the liquid levels in the wellbore from historical PLTs and density logs. In the field case studied, the analysis showed that the water vapor present in the fluid stream is a fundamental key to understand the evolution of fluid levels inside the wellbore. This is quite important since the water in the gas phase is not usually included in the EOS for reservoir simulation purposes and its impact in the wellbore dynamics is neglected because of the very low BSW (less than 1%). For the well that has been studied, the analysis revealed that the lower zone was prone to stop producing due to the higher productivity of the upper reservoirs. Consequently, the increase in liquid level was a result of the production decrease and not vice versa. After the lower layer stopped producing, it was observed that there was a quicker increase of the liquid column between the upper and lower reservoirs. This column was mostly condensate but it was gradually replaced by water in the liquid phase, which came from the vapor phase produced in the upper reservoirs. This slow replacement represents a more restrictive condition for the lower reservoir, as the column becomes denser. This study allowed for the understanding the complex interaction between retrograde condensation and water vapor behavior with the wellbore dynamics. The study also describes the process of the liquid accumulation during the decline of production of multilayered reservoirs which was successfully matched with observed data. As a result of the analysis, a new completion scheme was proposed to effectively recover the hydrocarbons in the layers affected by liquid loading issues.