Abstract

Asphaltene precipitation is caused by numerous factors such as changes in pressure, temperature, and composition. Drilling, completion, acid stimulation, and hydraulic fracturing activities can also induce precipitation in the near-wellbore region. Heavier crudes that contain a larger amount of asphaltene have very few asphaltene precipitation problems because they can dissolve more asphaltene. Thus, it is crucial to understand the significance of each uncertainty and control variables not only theoretically, but also with application to real-life examples such as with this model that uses a 32-degree API South American oil to demonstrate the importance of each variable to shed light in order to efficiently manage such reservoirs.

A commercial optimization and uncertainty tool is coupled with a full-physics commercial simulator that models the phenomenon in order to investigate the significance of major parameters on performance of wells in temperature-dependent asphaltene precipitation and irreversible flocculation. Temperature-dependent asphaltene precipitation and irreversible flocculation are modelled where no precipitation occurs at the original reservoir temperature, and flocculated asphaltene is allowed to deposit via surface adsorption and pore throat plugging. The exponent in the power law relating porosity reduction to the permeability resistance factor is modified to change the effect of asphaltene deposition on permeability reduction.

Lower temperatures are specified around the wellbore causing asphaltene precipitation. Sensitivity and optimization have been done on major reservoir parameters, such as, fluid and rock properties and well operational parameters, and significance of each has been illustrated in tornado diagrams. It is observed that a robust approach on handling of uncertainties in reservoir are as important as management of well operational parameters in the scope of reservoir management.

This study provides an in-depth optimization and uncertainty analysis to outline the significance of each major parameter involved in production performance and ultimately the recovery efficiency in reservoirs with temperature-dependent asphaltene precipitation and irreversible flocculation.

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