Natural Oil Depletion
The EUR during the natural oil depletion can be assessed with the following equation (see NDR @model for derivation):
| LaTeX Math Block |
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{\rm EUR}_O = \frac{Q_O}{V_O} = \frac{ (p_i - p_{wf}) \, c_t}{(1-s_{wi})\, B_o} =
\frac{ (p_i - p_{wf}) }{(1-s_{wi})\, B_o} \, \big( c_r + s_{wi} c_w + (1-s_{wi})c_o \big) |
where
| minimal flowing bottom-hole pressure |
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| initial formation pressure |
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| formation volume factor for oil, |
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| cumulative oil production |
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| STOIIP |
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| initial water saturation in oil pay |
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| total compressibility |
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For the naturally flowing wells the bottom hole pressure under flowing conditions can be roughly assed by homogeneous multiphase pipe flow model assessed as:
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p_{wf} = p_s + \rho_g \, g\, h + \bigg( 1- \frac{\rho_g}{\rho_o} \bigg) \, p_b |
where
– tubing-head pressure defined by the production gathering system,
– is the true vertical depth at formation top,
| LaTeX Math Inline |
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| body | \{ \rho_o, \, \rho_g \} |
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– oil and gas densities,
– bubble-point pressure.
Natural Gas Depletion
The Expected Ultimate Recovery during the natural gas depletion can be assessed with the following formula:
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EUR_{GD} = \frac{Q_g}{V_g} = 1- \frac{p_{wf}}{p_i} |
See also
Petroleum Industry / Upstream / Production / Field Development Plan / Recovery Methods
[ Waterflood Recovery (WF) ]
[ NDR @model ]
