cementing - salt solutions
DESCRIPTION
Cementing - Salt SolutionsTRANSCRIPT
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PETE 411
Well Drilling
Lesson 32
Cementing - Salt Solutions
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Cementing - Salt Solutions
Use of salt in Cement Slurries
Unsaturated Salt Solutions
Saturated Salt Solutions
Types Cements
Cement Additives
Examples
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Read:
ADE, Ch. 3
HW #15: Kick, W&W. Due Nov. 16, ‘05 HW #16: Cementing of Conductor Csg.
due November 21, 2005
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Salt in Cement Slurries
Salt Zones
Salt-saturated cements were originally used for cementing casing strings through salt zones.
Fresh or unsaturated salt cement slurries will not bond satisfactorily to salt formations because the slurry tends to dissolve or leach away the salt at the wall of the hole.
Salt-saturated cements will not dissolve any more salt so a good bond can be achieved
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Salt in Cement Slurries
Shale Zones
Many shales are sensitive to fresh water.
Salt helps to protect these shales in that it tends to prevent excessive sloughing or heaving of the shales.
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Salt in Cement Slurries
Accelerator
In low concentrations salt tends to accelerate the setting of cement.
Retarder
In high concentrations ( >5% by wt. of water) the salt will tend to retard the setting of the cement.
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Salt in Cement Slurries
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Salt in Cement Slurries
Expansion
Salt results in a more expansive cement.
Freezing
Salt reduces the freezing temperature of cement slurries.
9 of solution
EXAMPLE: 200,000 mg of NaCl 800,000 mg of H2O 1,000,000 mg of solution < 1 litre of solution
mg/L
ppm
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Volume of Sodium Chloride Solution
EXAMPLE: Adding 30 lbs of NaCl to 100 lbs of H2O increases the volume of solution by ~10.7%
30% by weight = 13.8% by volume (SG = 2.17) ??
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Density of Sodium Chloride Solution
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Sodium Chloride Solutions at 68 oF
0.96
0.98
1.00
1.02
1.04
1.06
1.08
1.10
1.12
1.14
0 10 20 30 40
Percent Sodium Chloride by Weight of Water
Volu
me
of S
olut
ion
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8.5
9
9.5
10
10.5
Dens
ity o
f Sol
utio
n, l
b/ga
l
1.068 9.36
, ga
l
20% NaCl 1.67 lbs NaCl / gal H2O 1.068 gal of solution 9.36 lb/gal
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Example: Salt Solutions
30% NaCl (by weight of water) is added to one gallon of fresh water. Calculate the density of the mixture:
(i) Before the salt goes into solution (ii) Using the solubility charts shown above.
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Problem : Salt Solutions
(i) Assuming that
lb/gal 9.51 mix =ρ
8.33) * (2.17 / 8.33) * (0.3011 x 8.33 * 0.301 * 8.33
++
=
mixmixSSWWmixmix2211 VρVρVρVρ...VρVρ =+=++
mix
SSwwmix V
VρVρρ +=
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Problem : Salt Solutions
(ii) From the chart, { 9.51 lb/gal vs. 9.8 lb/gal !! } { what if we had 60% salt? }
lb/gal 8.9mix =ρ
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Problem
Calculate the density and yield of a cement slurry consisting of:
65% Class “A” cement
35% Pozmix cement,
6% bentonite BWOC and
10.9 gal/sk of water.
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Problem
(i) Initial tabulations and calculations: Weight Specific Density Component lbs/sk Gravity lbs/gal Class “A” 94 3.14 8.33*3.14 = 26.16 Pozmix 74 2.46 8.33*2.46 = 20.49 Bentonite 2.65 8.33*2.65 = 22.07 Water 1.00 8.33*1.00 = 8.33
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Problem
(ii) Determine the properties of one sack of dry cement mixture; 65% Class “A” and 35% Pozmix:
(gal) Vol. (lbs) ht Weig Cement
3362.26.1661.1 61.194*0.65 sk 0.65 A,Class ==
2641.20.4925.9 25.974*0.35 sk 0.35 ,Pozmix ==
3.600 87.0
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Problem
(iii) Determine density and yield of final slurry:
14.7365 183.02
10.9 90.808.33*10.9 gal 10.9 Water,
2365.022.075.22 5.2287*0.06 6% Bentonite,
3.600 87.0 sk 1 mix, Cmt.
(gal) Vol. (lbs) Weight Component
=
==
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Problem
←==ρ lb/gal 42.1274.1402.183
mix
←= sk/ft 97.1 3
3gal/ft 48.7gal/sk 14.74Yield =