Page 113 - A Practical Companion to Reservoir Stimulation

PRACTICAL COMPANION TO RESERVOIR STIMULATION

EXAMPLE G-2
The Peclet number for radial geometry is given by
Calculation of Skin-Effect Reduction
in a Dolomite Reservoir

Calculate the skin-effect reduction in a dolomite reservoir
where the dolomite concentration is 60%. Acid, consisting of and thus
15% HCl, is to be used. The well, reservoir and treatment (1 BPM)(2.648 x 10’ cm’/s/BPM)
variables are presented in Table G- 1. Np, =
( cm2/s)( 100 ft x 30.48 cm/ft)
Solution (Ref. Sections 13-3 and 14-5) 4
The stoichiometric constant of the reaction between dolomite ’ = 8.69~ 10 . (G-4)
CaMg(CO& and HCl is 4. Findly, from Eq. 13- 13 and remembering that d = 2 for
First, the acid capacity number, Ac, is calculated from surface reaction limited kinetics (for dolomites),
Eq. 13-8. The acid concentration is 15% by weight. Thus, in
1 liter of solution (assuming p G 1 g/cm3)),

(150/36.5)
C= = 4.1 moles/liter, (G- 1)
1 liter (1.7 x 104)(56.8) 1
where 36.5 is the HCl molecular weight. The dolomite con- (3.14) (30.48)( 0.15) (0. 1)2
centration, since it is 60% by weight, can be calculated as
follows. = -4. ((3-5)
In 1 liter of rock, the total weight is 2650 g, of
which (2650 x 0.6) = 1590 g is dolomite. Since the molecular
weight of dolomite is equal to 184, its concentration is 1590/ q, = 1 BPM
184 = 8.64 moles/liter. Thus, from Eq. 13-8, the acid capacity
number is h = 100ft
I D = 10-5 cm*/s I
(0.15)(4.1)
Ac = = 0.018. I rw = 0.328ft=O.lm I
(4) (8.64)

Table G-1-Well, reservoir and treatment variables for
Example G-2.