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LaTeX Math Block
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p(t) = p_i + \int_0^t  p_u(t - \tau) dq = p_i + \int_0^t  p_u(t - \tau) \cdot q(\tau) d\tau


In case production history can be approximated by a finite sequence of constant rate production intervals (called Pressure Transients):

LaTeX Math Block
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p(t) = p_i + \sum_{\alpha = 1}^{N} \left[ q^{(\alpha)} - q^{(\alpha-1)} \right] \cdot p_u(t - t^{\alpha})

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LaTeX Math Inline
bodyp(t)

pressure at

LaTeX Math Inline
bodyn
-th well at arbitrary moment of time
LaTeX Math Inline
bodyt

LaTeX Math Inline
bodyp_i

initial pressure at

LaTeX Math Inline
bodyn
-the well

LaTeX Math Inline
body\alpha = 1 .. N

index number of a pressure transient (period of time where rate was constant) 

LaTeX Math Inline
bodyN

total number of transientstransients

LaTeX Math Inline
body--uriencoded--t%5e%7B\alpha%7D

starting point of the

LaTeX Math Inline
body\alpha
-th transient

LaTeX Math Inline
body--uriencoded--q%5e%7B(\alpha)%7D

rate value of

LaTeX Math Inline
body\alpha
-th transient which th transient which starts at the time moment 
LaTeX Math Inline
body--uriencoded--t%5e%7B(\alpha)%7D

LaTeX Math Inline
bodyp_u(t)

pressure transient response to  response to the unit-rate production (DTR)

with assumption:

  • LaTeX Math Inline
    body--uriencoded--q%5e%7B(-1)%7D = 0
    , which means that well was shut-in before it started the first transient 
    LaTeX Math Inline
    body\alpha =1
     

  • LaTeX Math Inline
    bodyp_u(t) = 0
     at 
    LaTeX Math Inline
    bodyt < 0
     which means pressure drop is zero before the well starts unit-rate production

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