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1
PETE 411Well 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:Applied Drilling Engineering, Ch. 3
HW #17Cementing of Liner
due November 27, 2002
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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 they tend to prevent excessive sloughing or heavingof 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.
9of solution
EXAMPLE:200,000 mg of NaCl800,000 mg of H2O1,000,000 mg of solution< 1 litre of solution
ppm
or m
g /L
mg/L
ppm
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Volume of Sodium Chloride Solution
EXAMPLE:Adding 30 lbs of NaClto 100 lbs of H2Oincreases 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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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 ====ρρρρ
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/galClass “A” 94 3.14 8.33*3.14 = 26.16Pozmix 74 2.46 8.33*2.46 = 20.49Bentonite 2.65 8.33*2.65 = 22.07Water 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
←←←←========ρρρρ lb/gal 42.1274.1402.183
mix
←←←←==== sk/ft 97.1 3
3gal/ft 48.7gal/sk 14.74Yield ====