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Figure 9. Reduced permeability at varying distance in the reservoir after | month.

Figure 9 Reduced permeability at varying distance in the reservoir after | month.

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The continuity equation can be simplified by assuming a constant local radial velocity, v), Paraffin Deposition Model
The continuity equation can be simplified by assuming a constant local radial velocity, v), Paraffin Deposition Model
Table 1. Composition of the sample used Table 2. Fluid and reservoir properties used as input in the simulation (Wang et al.,1999) Table 2 shows the fluid and reservoir properties used as input in the simulation performed n this study. The simulator was run at varying temperature at first, then at varying pressure Iso to see the effect of temperature and pressure on the amount of wax precipitated in the eservoir. Results from the program ms are shown in figure 1. Results obtained are validated Yy comparing with results generated through the use of analytical expression developed by ‘ing (1991) using the recombined separator liquid and gas whose composition is shown in ‘able 1 as a case study.
Table 1. Composition of the sample used Table 2. Fluid and reservoir properties used as input in the simulation (Wang et al.,1999) Table 2 shows the fluid and reservoir properties used as input in the simulation performed n this study. The simulator was run at varying temperature at first, then at varying pressure Iso to see the effect of temperature and pressure on the amount of wax precipitated in the eservoir. Results from the program ms are shown in figure 1. Results obtained are validated Yy comparing with results generated through the use of analytical expression developed by ‘ing (1991) using the recombined separator liquid and gas whose composition is shown in ‘able 1 as a case study.
Figure 1. Calculated and Experimentally determined weight of precipitated wax at varying temperature. a ~*~ From figure 2, it is seen that the wax weight fraction increases as the reservoir pressure decreases, as predicted by Ring et al.(1994) this phenomenon can be simply attributed to the loss of the lighter ends as the pressure in the reservoir is reduced. Wax precipitation alsc occurs by reducing the amount of dissolved gas in the liquid phase. Therefore, when the pressure of the reservoir fluid is dropped below the bubble point pressure which is the pressure at which the first bubble of gas leaves the surface of a liquid, the cloud point temperature of the fluid increases and there is a high tendency of wax to form.
Figure 1. Calculated and Experimentally determined weight of precipitated wax at varying temperature. a ~*~ From figure 2, it is seen that the wax weight fraction increases as the reservoir pressure decreases, as predicted by Ring et al.(1994) this phenomenon can be simply attributed to the loss of the lighter ends as the pressure in the reservoir is reduced. Wax precipitation alsc occurs by reducing the amount of dissolved gas in the liquid phase. Therefore, when the pressure of the reservoir fluid is dropped below the bubble point pressure which is the pressure at which the first bubble of gas leaves the surface of a liquid, the cloud point temperature of the fluid increases and there is a high tendency of wax to form.
Figure 2. Wax weight fraction at varying reservoir pressure at a temp. of 300K. As gas is released from solution with a reduction in gas saturation pressure, shrinkage of the liquid phase would begin to occur which has the effect of increasing the wax composition in the solid-liquid mixture and this causes the wax precipitation to increase as shown in figure
Figure 2. Wax weight fraction at varying reservoir pressure at a temp. of 300K. As gas is released from solution with a reduction in gas saturation pressure, shrinkage of the liquid phase would begin to occur which has the effect of increasing the wax composition in the solid-liquid mixture and this causes the wax precipitation to increase as shown in figure
Figure 3. Yearly wax deposition in the porous media at temperature of 300 K. From figure 3 shown, the amount of wax deposited in the first year was high and after which there was a sudden drop in the volume deposited to almost zero. This phenomenon can
Figure 3. Yearly wax deposition in the porous media at temperature of 300 K. From figure 3 shown, the amount of wax deposited in the first year was high and after which there was a sudden drop in the volume deposited to almost zero. This phenomenon can
Figure 4. Yearly wax deposition in the reservoir at 300 K for 10 years period. The wax deposited at varying distance (radius) from the wellbore is shown in figure 5. It can be seen that wax particles do not deposit much in the reservoir, this is due to lower pressure gradient in the reservoir, sizable amount of wax only deposit close to the well-bore where the pressure gradient is high This agrees with J N Ring et al. (1994) observation, that wax deposition is a near well-bore phenomenon.
Figure 4. Yearly wax deposition in the reservoir at 300 K for 10 years period. The wax deposited at varying distance (radius) from the wellbore is shown in figure 5. It can be seen that wax particles do not deposit much in the reservoir, this is due to lower pressure gradient in the reservoir, sizable amount of wax only deposit close to the well-bore where the pressure gradient is high This agrees with J N Ring et al. (1994) observation, that wax deposition is a near well-bore phenomenon.
Figure 6. Amount of wax deposited with distance from Ring, 1991 Analytical expression. Despite the ‘assumption the deposition profile still follows same trend (though with relatively higher percentage of predicted deposition wax) with the simulated results in figure -_
Figure 6. Amount of wax deposited with distance from Ring, 1991 Analytical expression. Despite the ‘assumption the deposition profile still follows same trend (though with relatively higher percentage of predicted deposition wax) with the simulated results in figure -_
Figure 7. Skin effect in the reservoir with time. As expected, the skin effect recorded though little was greatest at the near wellbore region. This is because the solid paraffin continues to buildup near the wellbore and production rate declines, therefore the most damage is done near the wellbore and that is also where there is a considerable decrease in the permeability of the reservoir to fluid flow. The skin caused by the paraffin deposition can be removed by electrical heating. This would increase the rate of oil production from the reservoir and also reduce the oil viscosity near the wellbore. Figure 7 shows the skin effect in the reservoir case being considered, it was observed that the skin effect decreases with time due to reduce in wax deposition with time. Figure 8 shows the variance of skin with reservoir distance, it can be seen that some appreciable effect is felt at the wellbore. The reduction in permeability recorded in this study is shown in figure 9. The figure closely agreed to that obtains by Wang et al. (1999). The reduction in permeability is attributed to the deposition of the precipitated wax in the pore spaces of the reservoir. As shown by the figure, the rate of permeability reduction increases near the well-bore where the effect of paraffin deposition is at its maximum. At the point where the effect of paraffin deposition ceases to be significant, the permeability reduction in the reservoir would cease and the rate tends to becomes constant. Figure 8 shows the variance of skin with reservoir distance, it can be seen that some
Figure 7. Skin effect in the reservoir with time. As expected, the skin effect recorded though little was greatest at the near wellbore region. This is because the solid paraffin continues to buildup near the wellbore and production rate declines, therefore the most damage is done near the wellbore and that is also where there is a considerable decrease in the permeability of the reservoir to fluid flow. The skin caused by the paraffin deposition can be removed by electrical heating. This would increase the rate of oil production from the reservoir and also reduce the oil viscosity near the wellbore. Figure 7 shows the skin effect in the reservoir case being considered, it was observed that the skin effect decreases with time due to reduce in wax deposition with time. Figure 8 shows the variance of skin with reservoir distance, it can be seen that some appreciable effect is felt at the wellbore. The reduction in permeability recorded in this study is shown in figure 9. The figure closely agreed to that obtains by Wang et al. (1999). The reduction in permeability is attributed to the deposition of the precipitated wax in the pore spaces of the reservoir. As shown by the figure, the rate of permeability reduction increases near the well-bore where the effect of paraffin deposition is at its maximum. At the point where the effect of paraffin deposition ceases to be significant, the permeability reduction in the reservoir would cease and the rate tends to becomes constant. Figure 8 shows the variance of skin with reservoir distance, it can be seen that some
Figure 8. Skin effect at varying distance in the reservoir after 1 month.
Figure 8. Skin effect at varying distance in the reservoir after 1 month.
Simulation of Paraffin Deposition in Petroleum Reservoirs Figure 10. Variation of productivity ratio with time in years in the reservoir. The figure shows the decline expected to be obtained in the reservoir due to the reduction in permeability and the skin damage recorded. These factors reduce the productivity index from that at the initial condition to a new state. The rate of decline increases as the number of years increases. It is advised that this reservoir should be stimulated to get the production of oil back to the initial if this is found economical.
Simulation of Paraffin Deposition in Petroleum Reservoirs Figure 10. Variation of productivity ratio with time in years in the reservoir. The figure shows the decline expected to be obtained in the reservoir due to the reduction in permeability and the skin damage recorded. These factors reduce the productivity index from that at the initial condition to a new state. The rate of decline increases as the number of years increases. It is advised that this reservoir should be stimulated to get the production of oil back to the initial if this is found economical.
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