1 PETE 411 Well Drilling Lesson 32 Cementing - Salt Solutions.

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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:

Applied Drilling Engineering, Ch. 3

HW #17 Cementing 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 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.

9of solution

EXAMPLE:200,000 mg of NaCl800,000 mg of H2O1,000,000 mg of solution < 1 litre of solution

pp

m o

r 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

8.33) * (2.17 / 8.33) * (0.301

1 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/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

3362.26.16

61.1 61.194*0.65 sk 0.65 A,Class

2641.20.49

25.9 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,

2365.022.07

5.22 5.2287*0.06 6% Bentonite,

3.600 87.0 sk 1 mix, Cmt.

(gal) Vol. (lbs) Weight Component

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Problem

lb/gal 42.1274.14

02.183mix

sk/ft 97.1 3

3gal/ft 48.7

gal/sk 14.74Yield