Difference between revisions of "Injectivity index"

Revision as of 12:19, 27 August 2026

I - well injectivity index characterizes how much water a well can inject per unit of pressure drop.

I is defined as follows:

{I} = \frac{q_{inj}}{P_{wf} - \bar{P}}

Thus, injection rate could be calculated as:

{q_{inj}} = {I}(P_{wf} - \bar{P})

From Darcy's law for an unfractured injection well located in the center of a circular drainage area, the I in pseudo-steady state is:

{I} = \frac{kh}{141.2 B \mu} {J_D} = \frac{kh}{141.2 B \mu} \times \frac{1}{ln{\frac{r_e}{r_w}-\frac{3}{4}+S}}

B

= formation volume factor, bbl/stb

I

= injectivity index, stb/psia or Mcf/psia

I_D

= dimensionless injectivity index, dimensionless

kh

= permeability times thickness, md*ft

\bar{P}_{inj}

= average injection pressure, psia

P_{wf}

= well flowing pressure (bottomhole), psia

q_{inj}

= injection rate, stb/d or Mcf/d

r_w

= wellbore radius, ft

r_e

= drainage radius, ft

S

= skin factor, dimensionless

\mu

= viscosity, cp

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 From [[Darcy's law]] for an unfractured injection well located in the center of a circular drainage area, the [[Injectivity index|I]] in pseudo-steady state is:
-:<math> {I} = \frac{kh}{141.2 B \mu} {I_D} = \frac{kh}{141.2 B \mu} \times \frac{1}{ln{\frac{r_e}{r_w}-\frac{3}{4}+S}} </math>
+:<math> {I} = \frac{kh}{141.2 B \mu} {J_D} = \frac{kh}{141.2 B \mu} \times \frac{1}{ln{\frac{r_e}{r_w}-\frac{3}{4}+S}} </math>
 == Nomenclature ==