PETE 411 Well Drilling

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PETE 411Well Drilling
Lesson 32Cementing - 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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ReadApplied Drilling Engineering, Ch. 3HW
17 Cementing of Linerdue 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 ( gt5 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.

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ppm or mg/L
mg/L
ppm
EXAMPLE 200,000 mg of NaCl 800,000 mg of
H2O 1,000,000 mg of solution lt 1 litre of
solution
of solution
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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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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

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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?

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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
  8.333.14 26.16
• Pozmix 74 2.46 8.332.46 20.49
• Bentonite 2.65
  8.332.65 22.07
• Water 1.00 8.331.00 8.33

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Problem

• (ii) Determine the properties of one sack of dry
  cement mixture 65 Class A and 35 Pozmix

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Problem

• (iii) Determine density and yield of final slurry

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Problem