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Bottom hole pressure of injection well is determined by
the formula
Р bh inj= wgH+ P inj -Р los pr , (4.8)
2
3
where  w – density of water ( w = 1000 kg/m ); g= 9.81 m/s -
acceleration of gravity; H – depth of injection well, m; P inj -
injection pressure, Pa; Р los pr - pressure loss due to friction,
which are determined by the Darcy-Weisbach equation, Pa.
Darcy-Weisbach equation has the form
H  2
P    , (4.9)
los
d 2 w
where λ - coefficient of hydraulic resistance that depends on the
Reynolds number and the roughness of the pipe, =f(Re, ); d -
the inner diameter of the pipe on which is pumping water; υ -
velocity of injected water.
The first, determine the velocity of movement
Q
 ,
F
2
where F - sectional area of the pipe, m .
Reynolds number is determined
d
Re  ,

where ν - kinematic viscosity of water.
If Re Re cr (Re cr =2320), then the mode of movement is
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laminar and λ determined by the Stokes formula  .
Re
If Re > Re cr (Re cr =2320), then the mode of movement
is turbulent and λ determined by the Blaziuses formula
, 0 3164
 .
Re , 0 25
Substituting equations (4.6) and (4.7) in (4.5), we obtain
an expression for the number of injection wells

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