Page 122 - A Practical Companion to Reservoir Stimulation

H. Diversion and Treatment Evaluation

EXAMPLE H-1 EXAMPLE H-2
Need for Diversion Diverter Pseudoskin

Calculate the required pseudoskin to be supplied by a diverter
to distribute the injection of acid based on the layer thicknesses
Layer k h S in Example H- 1.
1 10 md 20 ft ‘2
I I I I Solution (Ref. Section 15-5)
I 3 I 50md 1 30ft I 17 I To distribute the injected acid based on the thickness of each
layer, then
~
Calculate the distribution of acid to be injected. Use ln(re/rw)
= 8.

Solution (Ref. Section 15-1)
The initial flow rate injected in each layer (it will change as A similar expression can be written between Layers I and 3.
acid reacts and reduces the skin effect) is given by Eq. 14-6. Assuming that s,.,~~ for the zone that takes the least acid
Assuming that the pressure gradient is the same in each layer (Layer 1) is zero, then after simplification and substitution,
(grH - Ap,(,,? - p = constant) and B and p are the same, then [10/(8 + 2)]

kh I= [400/(8 + 8 + SdJ]’ (H-3)
[ In (r,IY,, ) + s I‘ resulting in s,,~~ 384. Similarly, between Layers 1 and 3,
9, Ot (H- 1)
=
Thus, using the given layer variable,
4/ = constant x 20 I= [ 10/(8 + 2)]
qz = constant x 250 [50/(8 + 17 + s,.,~~)]’
ql = constant x 60,
and the distribution would be resulting in s,,kr = 25.
Layer 1: 6%
Layer 2: 76%
Layer 3: 18%.
Layer 2, which is only 17% of the total formation, initially
takes more than 76% of all acid injected. This will deteriorate
during injection, as the skin effect in Layer 2 is reduced. On
the other hand, Layer 3, consisting of 50% of the formation,
takes less than 20% of the initial acid; hence, the need for
diversion.

H- 1