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PETE 411 Well Drilling. Lesson 32 Cementing - Salt Solutions. Cementing - Salt Solutions. Use of salt in Cement Slurries Unsaturated Salt Solutions Saturated Salt Solutions Types Cements Cement Additives Examples. - PowerPoint PPT Presentation
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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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Salt in Cement SlurriesSalt 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 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
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
mg/
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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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
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
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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