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RESEARCH PAPERS

# Asphaltene Near-well-bore Formation Damage Modeling

[+] Author and Article Information
Kosta J. Leontaritis1

AsphWax Inc., 12976 Sugar Ridge Boulevard, Stafford, Taxas 77477

1

Author Contact Information: Telephone: (281)-568-8444 Fax: (281)-568-8384. Email: kosta@asphwax.com

J. Energy Resour. Technol 127(3), 191-200 (Apr 01, 2005) (10 pages) doi:10.1115/1.1937416 History: Received March 18, 2004; Revised April 01, 2005

## Abstract

When during oil production the thermodynamic conditions within the near-well-bore 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, $λ$, $λ=ko∕μo=kkro∕μo$. Three possible mechanisms of asphaltene-induced formation damage have been discussed in the literature. 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, $μo$, by nucleating water-in-oil emulsions. In the most frequently encountered case of asphaltene-induced formation damage where 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 to represent the pore throat blockages. It also utilizes the Thermodynamic-Colloidal Model of Asphaltene, $TCModelSM$, an existing AsphWax asphaltene phase behavior model capable of simulating the asphaltene particle size distribution as a function of the thermodynamics of the system. 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 effect it has on near-well-bore and well-bore hydraulics. Similarly the model can be used to study a priori the economics of developing a reservoir known to contain under-saturated asphaltenic oil.

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## Figures

Figure 1

Aerial view of a producing well suffering from asphaltene-induced formation damage

Figure 2

Well producing with asphaltene-induced formation damage

Figure 3

Asphaltene deposition envelope AsphWax Oil Company Reservoir Oil

Figure 4

Asphaltene particle size distribution of the fluid in Fig. 3 calculated with the T-C Model at 5500 psia and 195°F

Figure 5

The near-well-bore region is divided into radial segments Δr. The formation damage calculation is performed for all segments at each time increment Δt

Figure 6

Pe and PAF remain constant while PW is declining. Flow, q, is constant. During time increment j, PW remains constant. Say for time increment 6, PW is P6, for time increment 4, PW is P4, etc.

Figure 7

Pressure profile at start of production

Figure 8

Progression of pressure profile with time inside the asphaltene-damaged formation

Figure 9

Progression of permeability profile with time inside the asphaltene-damaged formation

Figure 10

Progression of porosity profile with time inside the asphaltene-damaged formation

Figure 11

Simulated van Everdingen-Hurst skin factor caused by asphaltene-induced formation damage

Figure 12

Pressure profile at start of production

Figure 13

Progression of pressure profile with time inside the asphaltene-damaged formation

Figure 14

Progression of permeability profile with time inside the asphaltene-damaged formation

Figure 15

Progression of porosity profile with time inside the asphaltene-damaged formation

Figure 16

Simulated van Everdingen-Hurst skin factor caused by asphaltene-induced formation damage

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