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[[File:Vol4 page 0242 eq 002.png|RTENOTITLE]]....................(2) | [[File:Vol4 page 0242 eq 002.png|RTENOTITLE]]....................(2) | ||
'''Fig. | '''Fig. 4''' shows how flow restrictions in the near-wellbore region can increase the pressure gradient, resulting in an additional pressure drop caused by formation damage (Δ''p''<sub>skin</sub>). | ||
<gallery | <gallery> | ||
File:Vol4 Page 242 Image 0001.png|'''Fig. | File:Vol4 Page 242 Image 0001.png|'''Fig. 4—Pressure profile in the near-wellbore region for a well with formation damage.'''<ref name="r2" /> | ||
</gallery> | </gallery> | ||
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[[File:Vol4 page 0242 eq 003.png|RTENOTITLE]]....................(3) | [[File:Vol4 page 0242 eq 003.png|RTENOTITLE]]....................(3) | ||
Clearly, a flow efficiency of 1 indicates an undamaged well with Δ''p''<sub>skin</sub> = 0, a flow efficiency > 1 indicates a stimulated well (perhaps because of a hydraulic fracture), and a flow efficiency < 1 indicates a damaged well. Note that, to determine flow efficiency, we must know the average reservoir pressure, | Clearly, a flow efficiency of 1 indicates an undamaged well with Δ''p''<sub>skin</sub> = 0, a flow efficiency > 1 indicates a stimulated well (perhaps because of a hydraulic fracture), and a flow efficiency < 1 indicates a damaged well. Note that, to determine flow efficiency, we must know the average reservoir pressure,[[File:PR.PNG|middle|25x25px|PR]], and skin factor, ''S''. Methods to measure these quantities are discussed in [[Determination_of_flow_efficiency_and_skin|Determination of flow efficiency and skin]]. | ||
The impact of skin on well productivity can be estimated by the use of [[Reservoir_inflow_performance|inflow performance relationships]] (IPRs) for the well such as those proposed by Vogel, <ref name="r3">Vogel, J.V. 1968. Inflow Performance Relationships for Solution-Gas Drive Wells. J Pet Technol 20 (1): 83-92. http://dx.doi.org/10.2118/1476-PA</ref> Fetkovich, <ref name="r4">Fetkovich, M.J. 1973. The Isochronal Testing of Oil Wells. Presented at the Fall Meeting of the Society of Petroleum Engineers of AIME, Las Vegas, Nevada, 30 September-3 October 1973. SPE-4529-MS. http://dx.doi.org/10.2118/4529-MS</ref> and Standing. <ref name="r2">Standing, M.B. 1970. Inflow Performance Relationships for Damaged Wells Producing by Solution-Gas Drive. J Pet Technol 22 (11): 1399-1400. SPE-3237-PA. http://dx.doi.org/10.2118/3237-PA</ref> These IPRs can be summarized as follows<ref name="r5">Peters, E.J. 1990. Class notes. Department of Production Engineering, University of Texas at Austin (1990)</ref>: | The impact of skin on well productivity can be estimated by the use of [[Reservoir_inflow_performance|inflow performance relationships]] (IPRs) for the well such as those proposed by Vogel, <ref name="r3">Vogel, J.V. 1968. Inflow Performance Relationships for Solution-Gas Drive Wells. J Pet Technol 20 (1): 83-92. http://dx.doi.org/10.2118/1476-PA</ref> Fetkovich, <ref name="r4">Fetkovich, M.J. 1973. The Isochronal Testing of Oil Wells. Presented at the Fall Meeting of the Society of Petroleum Engineers of AIME, Las Vegas, Nevada, 30 September-3 October 1973. SPE-4529-MS. http://dx.doi.org/10.2118/4529-MS</ref> and Standing. <ref name="r2">Standing, M.B. 1970. Inflow Performance Relationships for Damaged Wells Producing by Solution-Gas Drive. J Pet Technol 22 (11): 1399-1400. SPE-3237-PA. http://dx.doi.org/10.2118/3237-PA</ref> These IPRs can be summarized as follows<ref name="r5">Peters, E.J. 1990. Class notes. Department of Production Engineering, University of Texas at Austin (1990)</ref>: | ||
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[[File:Vol4 page 0243 eq 001.png|RTENOTITLE]]....................(5) | [[File:Vol4 page 0243 eq 001.png|RTENOTITLE]]....................(5) | ||
When ''x'' = 0, a linear IPR model is recovered; when ''x'' = 0.8, we obtain Vogel's IPR; and when ''x'' = 1, Fetkovich's IPR model is obtained. An example of a plot for the dimensionless hydrocarbon production as a function of the dimensionless bottomhole pressure (IPR) is shown in '''Fig. | When ''x'' = 0, a linear IPR model is recovered; when ''x'' = 0.8, we obtain Vogel's IPR; and when ''x'' = 1, Fetkovich's IPR model is obtained. An example of a plot for the dimensionless hydrocarbon production as a function of the dimensionless bottomhole pressure (IPR) is shown in '''Fig. 5''' for different flow efficiencies. It is evident that, as flow efficiency decreases, smaller and smaller hydrocarbon rates are obtained for the same drawdown [[File:Vol4 page 0243 inline 001.png|RTENOTITLE]]. | ||
<gallery | <gallery> | ||
File:Vol4 Page 243 Image 0001.png|'''Fig. | File:Vol4 Page 243 Image 0001.png|'''Fig. 5—Inflow performance relations for different flow efficiencies(F).'''<ref name="r3" /> | ||
</gallery> | </gallery> | ||
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