Experimental Study on Asphaltene-Induced Formation Damage

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractApplication of many EOR technologies provokes productivity decline due to asphaltene deposition leading to wellbore plugging and flow restriction in tubing, flow lines and production facilities. The present study aims at investigating the kinetics of asphaltene deposition using both model system and actual crude oil. Experiments were performed by injecting asphaltenic fluids into capillaries and outcrop sandstones. The effect of flow rate, presence of resins and asphaltene aggregation were investigated.It was experimentally evidenced that asphaltene deposition is a continuous process that results in multilayer deposition. It was demonstrated that asphaltene deposition takes place according to the well-known scaling law of Diffusion Limited Deposition (DLD) regime. The results demonstrated that multilayer deposition might be hindered by shear rate. It was shown that, above a first critical shear rate (lower critical shear rate) that depends on asphaltene aggregation state, the multilayer deposition kinetic is slowed down upon increasing injection flow rate. The flow rate dependence switches from -2/3 to -5/3 power law. This latter exponent is thought to encompass the classical -2/3 dependence of the DLD regime and the effect of asphaltene detachment that, therefore, varies as the flow rate to the power -1. The results put into evidence the existence of an upper critical shear rate value beyond which multilayer deposition is totally hindered. The value of this critical shear rate depends on resin content and varies exponentially with solvent quality.In conclusion, the experimental results showed that the "colloidal approach" is a valuable route for asphaltene deposition modeling that can be used to develop a more realistic asphaltene near-wellbore damage model that takes into account the actual physics of the process.L. Nabzar, M.E. Aguilera, and Y. Rajoub, Inst. Français du Pétrole

The Colloidal Approach. A Promising Route for Asphaltene Deposition Modelling

“…These include, first, a model system that consisted in Safania asphaltene dissolved in toluene and capillaries and more representative systems that consisted in three different crude oils (Weyburn, Hassi Messaoud and Arabian light) and Fontainebleau sandstones. Regarding model system and Weyburn crude oil, it was concluded that [15]: -Asphaltene deposition kinetics, indeed obeys the scaling law of the colloidal approach. -In the asphaltene deposition process, two main deposition regimes have been distinguished: -At low shear rate, and up to a first critical value (lower critical shear rate: γ cl ), the deposition is mainly diffusion-controlled and obeys the classical s = 2/3 power law (Equation 3 above) of the Diffusion Limited Deposition regime.…”

“…Moreover, it was clearly demonstrated that this shear rate limitation results from a dynamic equilibrium between hydrodynamic and adhesion forces. Recently [15,18], a systematic and thorough experimental investigation of the asphaltene deposition kinetics has been performed using different systems and under different experimental conditions. These include, first, a model system that consisted in Safania asphaltene dissolved in toluene and capillaries and more representative systems that consisted in three different crude oils (Weyburn, Hassi Messaoud and Arabian light) and Fontainebleau sandstones.…”

“…Nabzar et al [12][13][14][15] proposed a new approach for asphaltene deposition modeling that is called the "Colloidal Approach" and based on the theory of colloid transport and deposition in porous media and taking into account the specific feature of asphaltene particles such us their loose structure and their tendency to form multilayer deposition. This colloidal approach has been used successfully to model the deposition kinetics of different kind of colloid such as solid particles [16] and emulsion droplets [17].…”

“…This colloidal approach has been used successfully to model the deposition kinetics of different kind of colloid such as solid particles [16] and emulsion droplets [17]. This approach has been recently [15,18] experimentally validated through a systematic and thorough experimental investigation of the asphaltene deposition kinetics using different systems and under different experimental conditions. These include both model system that consisted in Safania asphaltene dissolved in toluene and capillaries and more representative system that consisted in Weyburn crude oil and Fontainebleau sandstones.…”

Multifunctional Evaluation of a New Supramolecular Complex in Enhanced Oil Recovery, Removal/Control of Organic Damage, and Heavy Crude Oil Viscosity Reduction

“…Asphaltenes can deposit both in the producing slots and in the formation face. Deposition of asphaltene precipitates over pore surface and/or across pore throats may reduce the effective pore space and/or severely impair the ability of oil to flow through porous formation, altering the rock wettability from water-wet to oil -wet, and increasing hydrocarbon viscosity by nucleating water-in-oil emulsions [1][2][3][4][5] . On the other hand, enhanced oil recovery (EOR) processes have become increasingly important to the petroleum industry.…”