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Clearly all wells do not exhibit exponential behavior during depletion. In many cases a more gradual hyperbolic decline is observed where rate time performance is better than estimated from exponential solutions implying that hyperbolic decline results from natural and artificial driving energies that slow down pressure depletion. Hyperbolic decline is observed when reservoir drive mechanism is solution gas cap drive, gas cap expansion or water drive. It is also possible where natural drive is supplemented by injection of water gas. The type of decline and its characteristic shape is a major feature of DCA. We shall be talking more about this as we go further. The various types of declines experienced by a well are documented in the '''Fig 1 and Fig 2'''. | Clearly all wells do not exhibit exponential behavior during depletion. In many cases a more gradual hyperbolic decline is observed where rate time performance is better than estimated from exponential solutions implying that hyperbolic decline results from natural and artificial driving energies that slow down pressure depletion. Hyperbolic decline is observed when reservoir drive mechanism is solution gas cap drive, gas cap expansion or water drive. It is also possible where natural drive is supplemented by injection of water gas. The type of decline and its characteristic shape is a major feature of DCA. We shall be talking more about this as we go further. The various types of declines experienced by a well are documented in the '''Fig 1 and Fig 2'''. | ||
INSERT FIGURE 1 q vs. Time showing various types of declines on Cartesian plot. (b value for hyperbolic curve =0.5) INSERT FIGURE 2 Log q vs. Time showing various types of declines on Semilog plot. (b value for hyperbolic curve =0.5). Note change in shapes of curves. | INSERT FIGURE 1 q vs. Time showing various types of declines on Cartesian plot. (b value for hyperbolic curve =0.5) | ||
INSERT FIGURE 2 Log q vs. Time showing various types of declines on Semilog plot. (b value for hyperbolic curve =0.5). Note change in shapes of curves. | |||
Observe the change in Shapes of curve from Cartesian to logarithmic; this is very helpful in identification of type of decline. | Observe the change in Shapes of curve from Cartesian to logarithmic; this is very helpful in identification of type of decline. | ||
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Two sets of curves are normally used while analyzing production decline. | Two sets of curves are normally used while analyzing production decline. | ||
#Flow rate is plotted against Time:<ol start="1" style="list-style-type: lower-alpha;"> | #Flow rate is plotted against Time:<br/><ol start="1" style="list-style-type: lower-alpha;"> | ||
<li>Very convenient since it provides future profiles directly.</li> | <li>Very convenient since it provides future profiles directly.</li> | ||
</ol><li>Flow rate against cumulative production:<ol start="1" style="list-style-type: lower-alpha;"> | </ol><li>Flow rate against cumulative production:<br/><ol start="1" style="list-style-type: lower-alpha;"> | ||
<li>Able to incorporate impact of intermittent operations that impact production.</li> | |||
<li>Provide recovery estimates at a specific economic limit.</li> | <li>Provide recovery estimates at a specific economic limit.</li> | ||
</ol></li> | </ol></li> | ||
</ol> | </ol> | ||
INSERT FIGURE 3 Rate verses Time and Rate verses Cum Oil | INSERT FIGURE 3 Rate verses Time and Rate verses Cum Oil | ||
== References == | == References == | ||
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