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Integral-average Average reservoir pressure over the drainage volume 

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bodyV_e
:

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p_r = \frac{1}{V_e} \iint_{A_e} p(x,y,z) dSdV


For the steady state flow in Steady State Radial Flow in finite reservoir the relationship between Boundary-average formation pressure 

LaTeX Math Inline
bodyp_e
 and Field-average Drainarea formation pressure 
LaTeX Math Inline
bodyp_r
 is going to be:

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p_r = p_i +- \frac{q_t}{24 \pi \sigma} \bigg[ \ln \frac{r_e}{r_w} -0.5 \bigg]
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BXEPW
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V_e = \pi r_e^2 h, \quad dV = 2\pi r \, h
,
 dr 
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pr1
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p_r = \frac{1}{V_e} \int p(r) dV = \frac{2}{r_e^2} \int p(r) \, r \, dr

For the Steady State Radial Flow in finite reservoir the reservoir pressure is going to be:

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p(t,r) = p_e(t) + \frac{q_t}{2 \pi \sigma} \, \ln \frac{r}{r_e} = p_i + \frac{q_t}{2 \pi \sigma} \, \ln \frac{r}{r_e}

and substituting the above to

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anchorpr1
and integrating:

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p_r =  \frac{2}{r_e^2} \int \bigg[ p_i 
-
+ \frac{q_t}{2\pi \sigma} \ln \frac{r}{r_
w
e} \bigg] \, r \, dr = p_i - \frac{q_t}{4\pi \sigma}


For the Pseudo-Steady State Radial Flow in finite reservoir the relationship between Boundary-average formation pressure 

LaTeX Math Inline
bodyp_e
 and Drainarea formation pressure 
LaTeX Math Inline
bodyp_r
 is going to be:

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p_r(t)= p_e(t) - 0.75 \cdot \frac{q_t}{2 \pi \sigma}
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titleDerivation
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LaTeX Math Block
anchorBXEPW
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V_e = \pi r_e^2 h, \quad dV = 2\pi r \, h dr 
LaTeX Math Block
anchorpr1
alignmentleft
p_r = \frac{1}{V_e} \int p(r) dV = \frac{2}{r_e^2} \int p(r) \, r \, dr

For the Pseudo-Steady State Radial Flow in finite reservoir the reservoir pressure is going to be:

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p(r) = p_i + \frac{q_t}{4 \pi \sigma} \, \left[ 2 \ln \frac{r}{r_e} - \frac{r^2}{r_e^2} \right]

and substituting the above to

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anchorpr1
and integrating:

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anchorBXEPW
alignmentleft
p_r(t) =  \frac{2}{r_e^2} \int \bigg[ p_e(t) + \frac{q_t}{4\pi \sigma} \left[ 2 \ln \frac{r}{r_e} - \frac{r^2}{r_
w
e^2} 
-1
\right] \bigg] \, r \, dr = p_i - 0.75 \cdot \frac{q_t}{2\pi \sigma}


See Also

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Petroleum Industry / Upstream / Production / Subsurface Production / Well & Reservoir Management / Formation pressure (Pe)

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