The EUR during the natural oil depletion can be assessed with the following equation (see NDR @model for derivation):
{\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 | |
| initial formation pressure | |
| formation volume factor for oil, | |
| cumulative oil production | |
| STOIIP | |
| initial water saturation in oil pay | |
| total compressibility |
For the naturally flowing wells the bottom hole pressure under flowing conditions can be roughly assed by homogeneous multiphase pipe flow model assessed as:
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,
– oil and gas densities,
– bubble-point pressure.
The Expected Ultimate Recovery during the natural gas depletion can be assessed with the following formula:
EUR_{GD} = \frac{Q_g}{V_g} = 1- \frac{p_{wf}}{p_i} |
Petroleum Industry / Upstream / Production / Field Development Plan / Recovery Methods
[ NDR @model ]