Integrated Approach Combining Plant Data and Thermodynamic Simulation for Management of Inorganic Scale in Topsides Processing Facilities

Abstract

Abstract A major concern with pre-salt processing is the water salinity and its high scaling potential. High standing output levels necessitate an effective scaling management strategy. One element of a successful program is scale prediction, which is frequently done utilizing the produced water's thermodynamic equilibrium. This paper presents a methodology and algorithm to systematically calculate scaling index of produced water blend to be compared to representative brines which were defined for scaling inhibitor design tests. Thermodynamic calculations of calcite saturation indexes at relevant process conditions are evaluated for the mixture of produced wells streams and for the platform critical brine. It was implemented an algorithm that integrates plant historian database to thermodynamic calculation routines and presents the results in a user-friendly web portal for proper visualization. Calcite saturation index is calculated using Pitzer activity model which is often used for calculations of inorganic scaling potential in high ionic waters. Produced wells flowrates are used for defining mixture fractions of the produced blend. For each platform there is one representative brine composition that was used for scale inhibitor design, herein called the platform critical brine. However, the compositions of wells produced water are updated as soon as new water analysis is available. The algorithm creates a scaling index (ISS) based on calcite saturation indexes that measures how far from the critical brine the produced mixture is in relation to calcite saturation index. The ISS is evaluated systematically in daily basis for several platforms offshore Brazil. The results show how the different wells configurations (flowrates) impact the produced water blend criticality with respect to inorganic scaling. The implemented routine gives insight to production engineering personnel regarding potential problems with scaling and chemicals design. It can be used to assess if the platform critical brine should be updated, and possibly new chemicals designed. Additionally, the ISS can be used to optimize the topsides process conditions in specific scenarios. The processing conditions and produced water compositions of pre-salt oilfields offshore Brazil results in scaling potential at topsides. This paper describes the methodology applied for monitoring the scaling potential systematically on a daily basis for several pre-salt platforms.