Abstract

Asphaltene precipitation is caused by numerous factors such as temperature, pressure and compositional vartiations. Drilling, completion, acid stimulation, and hydraulic fracturing activities can also result in settling in the near-wellbore region. Heavier crudes have a fewer precipitation issue becasue of dissolving 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 combined with a full-physics commercial simulator, which can create a model to investigate the significance of major factors influencing the 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 through 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. And then, optimization and sensitivity have been performed on major reservoir parameters including well operational parameters, and fluid and rock properties. Moreover, each parameter has been demonstrated in tornado diagrams. It was concluded that employing feasible methods on handling of reservoir uncertainties are as important as management of well operational parameters for effective 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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