A Multidisciplinary Approach Including Reservoir Engineering, Petrophysics and Well Performance for a Better Scaling Risk Management in HPHT Wells

The interventions on wells such as cleaning and reperforations improve production but not for a long period of time. CaCO₃ scale could be the reason for the decline of production; it is therefore crucial to understand the production issues with the objective to design better future wells. The aims of this study are the evaluation of the scaling risk and determination of any link between decline of production, before well intervention, with the scale deposit.

A multidisciplinary approach where analyses from several disciplines such as reservoir engineering, petrophysics and well performance are used for a better scaling risk management in the wells.

This study concerns an Ultra HPHT deep gas condensate Southeast Asian field. No formation water is available; therefore, an analog water has been used for the evaluation of the scaling risk; this water is characterized by a low level of barium; therefore, barium sulphate scaling risk is not expected. The scaling risk has been modelled for the bottomhole and wellhead for individual wells. The results have been analyzed together with the evolution of the production data associated with well interventions. The scaling risk assessment has shown a moderate to a high risk of CaCO₃ at bottomhole. The decline of production could be explained by the deposition of CaCO₃ at bottomhole, blocking the perforations, this is due to a high drawdown. To reduce the CaCO₃ scaling risk at bottomhole, it is recommended to reduce the current drawdown and maintain the bottomhole flowing pressure above the recommended value, depending to individual wells. Some evaporation of the formation water is also possible due to the very high temperature of this Ultra HPHT reservoir. In addition to the reduction of the current drawdown, it is recommended to perform a curative treatment with a help of bull-heading acid wash treatment as soon as a reduction of production is observed. This treatment will help to dissolve the CaCO₃ scale at bottomhole, at the perforations and tubing. The scaling risk evaluation shows that as soon as water is produced there is a risk of formation of CaCO₃ scale. This risk occurs even with very low production water flowrate. A complementary study including the analysis of the mineralogy and petrophysics of the reservoir, production data, water composition and prediction of the scaling risk has helped to identify the causes of the production decline and propose an adapted scaling risk mitigation for individual wells.