Formation Damage Caused by Asphaltene Deposition in a well of Carbonate Reservoir

Saeed Sajjadian¹ Vahid Mahmoudian Ataabadi²

1) Engineer of NIOC
2) Engineer of NIOC

Publication : 2nd International Conference On Research Science And Technology(2rstconf.com)
Abstract :
When during oil production the thermodynamic conditions within the near-wellbore formation lie inside the asphaltene deposition envelope of the reservoir fluid, the flocculated asphaltenes cause formation damage. Mathematically, formation damage is a reduction in the hydrocarbon effective mobility, λ (λ=ko/μ=kkr/μ). Asphaltenes can reduce the hydrocarbon effective mobility by a) blocking pore throats thus reducing the rock permeability, k, b) adsorbing onto the rock and altering the formation wettability from water-wet to oil-wet thus diminishing the effective permeability to oil, ko, and c) increasing the reservoir fluid viscosity, μ, by nucleating water-in-oil emulsions. In the most frequently encountered case of asphaltene-induced formation damage where an under-saturated oil is being produced without water, the most dominant damage mechanism is blockage of pore throats by asphaltene particles causing a reduction in rock permeability k. This paper presents a rather simple, yet realistic way of modeling asphaltene-induced near-well formation damage caused by blockage of pore throats by asphaltene particles. The model utilizes both macroscopic and microscopic concepts of the pore throat blockages. It also utilizes an existing asphaltene phase behavior model. The new asphaltene near-well formation damage model is applied in one case where it is used to track the degree of formation damage as a function of time and the effects on near-wellbore and wellbore hydraulics. Similarly the model can be used to preliminary study of the economics of developing a reservoir known to contain an under-saturated asphaltenic oil.
Keywords : Formation damage Near wellbore Particle size