This paper is concerned with ASPHALTENE DEPOSITION in fluid flowing through pipelines. Brownian diffusion and drag, gravitational, thermophoresis, buoyancy, and shear removal are considered as possible mechanisms in the ASPHALTENE DEPOSITION process. The thermo-physical properties of the fluid were obtained from Iranian oil fields. A model was used in the pipeline DEPOSITION modeling to predict the ASPHALTENE DEPOSITION rates under flow conditions. The effects of particle size, temperature gradient, and fluid velocity were studied on ASPHALTENE DEPOSITION rate. The results showed that, among the above-mentioned mechanisms, the gravitational and thermophoresis forces played a significant role in the formation of the deposit under the flow conditions. To verify the model, some predictions were compared with the available aerosol DEPOSITION data in the literature.

In this paper, a setup for performing dynamic flow experiments was prepared. A set of natural depletion tests were done to investigate the effects of pressure depletion and the initial ASPHALTENE content of crude oils on ASPHALTENE DEPOSITION in porous media using two live oil samples of Iranain reservoirs. The results of these experiments, which were done in constant rate and three pressure steps, show that the ASPHALTENE DEPOSITION occurs by decreasing pressure in the vicinity of bubble point pressure and the main mechanisms are surface DEPOSITION, pore throat plugging and in some period the entrainment of the particles via the flow of oil is observed. According to the experiments, in case of the oils with less ASPHALTENE content, the dominant mechanism is surface DEPOSITION, and the rate of DEPOSITION is uniform, while using the crude oil with higher ASPHALTENE content, the pore throat plugging mechanism has more important role in the permeability reduction of reservoir rock.

ASPHALTENE precipitation and DEPOSITION is a serious problem in many Iranian fields. The deposited ASPHALTENE results in partial or total blockage of the wellbore and wellstring reducing or completely seizing oil production. This paper studies the ASPHALTENE problem and mitigation methods in wellstring systematically. It presents new approach based on the combination of thermodynamic modeling of ASPHALTENE precipitation with hydrodynamic well modeling. The developed model is capable to determine the ASPHALTENE precipitation and DEPOSITION interval through the wellstring. Therefore, it could study the effect of hydrodynamic parameters such as wellhead pressure, well flow-rate and tubing size on the mitigation of ASPHALTENE DEPOSITION. The conventional way to treat ASPHALTENE DEPOSITION was through remediation which attacks the problem after it occurs. This model is capable to determine the severity of ASPHALTENE DEPOSITION even before start of production. The model was applied to simulate the ASPHALTENE precipitation in one of the south Iranian oil fields (Kupal) and important guidelines have been studied to mitigate the risks associated with ASPHALTENE DEPOSITION. The results of modeling show that change in hydrodynamic condition could reduce and mitigate ASPHALTENE DEPOSITION damage. But in some cases it would not be possible to prevent ASPHALTENE precipitation completely. Therefore, the approach for flow assurance in those cases would be to change the well completion and inject ASPHALTENE inhibitor, in order to prevent DEPOSITION of ASPHALTENE flocculates.

In this work the likelihood of ASPHALTENE DEPOSITION problems during dynamic displacement of oil by natural gas in unconsolidated porous media is experimentally inspected. The two different rock materials, limestone and sandstone, are used as a representative of porous media. Dynamic flow experiments indicate that the increase of natural gas injection increases ASPHALTENE DEPOSITION in the unconsolidated matrix. The results of the study show that increase in ASPHALTENE DEPOSITION leads to pore plugging, porosity reduction and absolute permeability damage. Irreducible water measurements showed that natural gas-induced ASPHALTENEs change the rock wet ability to oil-wet.

In this research, the ASPHALTENE particles DEPOSITION are modeled using species transport equations. It is assumed that the DEPOSITION phenomenon consists of two steps: transport of ASPHALTENE particles toward the wall and attachment of them to the wall. Due to the small size of ASPHALTENE particles, their motion are simulated using species transport equations. The transport phenomenon of ASPHALTENE particles are modeled by turbulent and Brownian diffusion and the attachment mechanism is modeled by employing first order chemical reaction near the surface. Effects of surface temperature and velocity are also considered in the model. Finally, the effects of important parameters such as velocity, surface temperature and ASPHALTENE concentration on DEPOSITION rate are investigated and compared with experimental data. The simulation results are agreed well with experimental data and the maximum error of the model is about 20 percent. Also in addition of DEPOSITION rate, transport and attachment rate are investigated. The predicted trend of transport rate agrees well with mass transfer equations for fully developed turbulent flow but the model has the average error of 15 percent. The prediction error is due to the under developing assumption in the computational model. The results indicate that the attachment mechanism is more important than transport. Therefore, accurate modelling of attachment has significant effects on prediction of ASPHALTENE DEPOSITION rate.

In this work, the precipitation and re-dissolution of ASPHALTENEs were studied for an Iranian relatively heavy crude oil. A series of experiments were designed and carried out to quantitatively examine the reversibility of ASPHALTENEs precipitation upon the change in the solvent concentration along with the temperature. n-Heptane was used as the precipitant, and a temperature range of 30 to 70°C was applied to perform the temperature reversibility tests. Experiments were conducted in both porous and non-porous media. As a porous medium, a slim tube apparatus was used which is a one- dimensional model reservoir. Generally, the experiments showed that the precipitation is completely reversible for oil under study upon both composition and temperature changes.

A static to dynamic approach to modeling ASPHALTENEs has been developed and validated. A new algorithm for static ASPHALTENE modeling uses a multi-solid thermodynamics approach where the equality of fugacity for each component and phase is applied at equilibrium conditions. This is required for minimizing the Gibbs free energy. The fractal distribution function used for the splitting and characterization of heavy components provides accurate results. The precipitation and re-dissolution of ASPHALTENEs are investigated for a relatively heavy crude oil from an Iranian field. A series of experiments are designed and carried out quantitatively to obtain the permeability reduction in a slim tube. Using a dynamic reservoir simulator, a 3- dimensional ASPHALTENE model is developed to simulate the precipitation, flocculation, DEPOSITION and its impact on permeability in a slim tube. With this approach, the ASPHALTENE is defined as a set of component(s) that can precipitate depending on their molar percentage weight in the solution. The simulated permeability reduction due to ASPHALTENE DEPOSITION shows good agreement with our experimental data.

Inhibitor treatment is an effective method for ASPHALTENE DEPOSITION control in petroleum industries. ASPHALTENE dispersant test is an appropriate method to select the inhibitor type and inhibition evaluation on DEPOSITION phenomenon control. The performance of some vegetable oils on ASPHALTENE DEPOSITION control of two Iranian crude oils is evaluated. The nut and wheat germ oils have excellent results on these crude oils. Results show these compounds in the concentration of 18000 ppm and more of that can perfectly remove of ASPHALTENE precipitation of two crude oil samples.