(56d) Quantifying Asphaltene Impairment Risks During Front End Engineering Design

Asphaltenes precipitation and deposition occur within both reservoirs and production systems, posing serious operational and economic risks in numerous developments worldwide.  Traditionally, these risks are assessed strictly on a thermodynamic basis.  Laboratory tests of varying degrees of sophistication are used to identify asphaltenes-onset conditions, these are compared with the thermal-hydraulic and compositional path of the fluid system, and chemical intervention or process selection are specified accordingly.  To the extent that such data are valid, this approach is “correct” in the sense that it provides for prevention or remediation downstream of the point of asphaltenes occurrence within a system.  However, this approach cannot provide quantification of impairment rates or severity, as required for a rigorous, probabilistic cost-benefit analysis of competing management strategies.  To help address this deficiency, deposition-kinetics analysis tools have recently come into use; however, their application tends to be semi-quantitative (as in chemical screening), and issues of scale-up and validation limit their direct applicability and generalization to FEED-scale system analysis.  Finally, it is generally untenable to use a purely comparative/experiential approach to asphaltenes-management planning, because asphaltenes behavior is highly system-specific, and because historical operational data for asphaltenes impairment are generally very limited in quantity, quality and/or detail. 

This paper presents a workflow methodology by which novel mechanistic modeling tools for asphaltenes deposition, within both porous-media and pipe/tubing flow environments, can be used to address the existing gaps in technology and field experience in planning for asphaltenes management.   Using a combination of laboratory analysis, reservoir- and production-simulation tools, and sensitivity analysis, it is possible to quantify the range of probable levels of productivity impairment due to asphaltene phenomena, and their economic significance.  This in turn provides a basis for optimization of the asphaltenes management strategy – which might include process design considerations, such as modifications to recovery and lift methods, along with direct intervention/remediation protocols such as periodic or continuous chemical inhibition, solvent treatments, or other stimulation, cleaning and workover operations.  This approach can provide for greatly reduced risk and uncertainty associated with the FEED analysis of asphaltene-prone developments.