Enhanced Evaluation of Asphaltene-Related Oil Properties To Facilitate Production in a Complex Offshore Environment

Asphaltene destabilization is a widespread problem in the oil industry. Under initial pressure and temperature conditions in the oil reservoir, asphaltenes are stabilized by building micelle structures in which they are associated with resin and aromatic compounds. Stable asphaltenes do not pose problems during oil production; however, if pressure/temperature conditions change throughout the production system, asphaltenes might become destabilized. Once destabilized, asphaltenes can potentially impair the whole production system. The development and implementation of a profound chemical injection strategy to mitigate asphaltene-related problems are paramount for a successful and sustainable fluid production if routine operating conditions are within the asphaltene instability range. A preventive asphaltene mitigation strategy is generally preferred; i.e., it is beneficial to avoid the occurrence of asphaltene-related problems in the first instance, instead of applying any remediation method afterward. Boundary conditions defined by the oil characteristics and the actual production conditions can make the development of a completely preventive chemical treatment strategy challenging. This applies especially in the offshore sector of the industry with given limitations in accessibility to the production and storage facilities accompanied by stringent regulatory requirements. This paper describes the analysis of a crude oil produced in a complex offshore environment, including mixing with condensate and storage in a gravity-based subsea tank. It highlights the asphaltene-related characteristics and compares different technologies to assess stability of the oil in neat form and upon mixing with condensate. The impact of different asphaltene inhibitors/dispersants on the oil has been investigated, and additionally, the effectiveness of dissolver chemicals on artificially sedimented asphaltene deposits has been evaluated. Different lab experiments have been conducted to determine the asphaltene concentration in the fluid and sediment layer over time with the aim to quantify the sedimentation. Computational fluid dynamics (CFD) was used to simulate potential sedimentation phenomena. This paper is based on a presentation given at the 19th International Conference on Petroleum Phase Behavior and Fouling (Petrophase 2018) in Park City, UT, U.S.A. Names of the platforms, distinct locations, and actual production numbers are not revealed in the paper with respect to information protection requirements of the parties involved.