Asphaltene Studies in on-shore Abu Dhabi Oil fields, PART III: Optimization of Field Chemicals for Remediation and Inhibition of Asphaltene Deposition

Abstract

Abstract The selection of a chemical solution to asphaltene challenges is an integral part of the flow assurance strategy, and has direct impact on both CAPEX and OPEX. The chemical selection process includes a detailed analysis of deposits, measurements of crude oil properties and various stock tank liquid tests, which are essential input into the development of the most appropriate inhibition and/or remediation strategy. The success of the chemical treatment strategy is a collaborative effort between operations and technology experts. In an onshore field in Abu Dhabi, routine clean-up jobs to date consist of diesel solvent as a carrier mixed with a dispersant chemical in approximately 80:20 proportions. However, the field observations indicate that such an approach provides often limited effect and sometimes can be detrimental for the well due to fluid incompatibilities. Laboratory tests on deposits collected from this field, combined with Shell’s extensive experience in the area of asphaltenes prevention/remediation led firstly to identification of an alternative aromatic-rich solvent. In addition, better performing dispersant chemicals than previously used were identified that could increase the overall efficiency of the cleaning jobs (soaks, washes). In order to reduce the frequency of clean-up operations for wells with severe asphaltene problems, continuous application of chemicals (inhibitors) has been considered. Asphaltene inhibitors may not completely prevent asphaltene precipitation but may significantly "delay" the process of deposition. Lab inhibitor testing was performed on crude oil samples collected from the Abu Dhabi field and the performance of the chemicals with respect to their concentration was evaluated. The best inhibitor from the lab testing will be applied in a field trial where the dosage is optimized following a proper surveillance plan to monitor the chemical effectiveness.