Lesson 32 Cementing - Salt Solutions 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

Read: Applied Drilling Engineering, Ch Read: Applied Drilling Engineering, Ch. 3 HW #17 Cementing of Liner due November 27, 2002

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

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.

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.

Salt in Cement Slurries

Salt in Cement Slurries Expansion Salt results in a more expansive cement. Freezing Salt reduces the freezing temperature of cement slurries.

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

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)

Density of Sodium Chloride Solution

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.

Problem : Salt Solutions (i) Assuming that

Problem : Salt Solutions (ii) From the chart, { 9.51 lb/gal vs. 9.8 lb/gal !! } { what if we had 60% salt? }

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.

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

Problem (ii) Determine the properties of one sack of dry cement mixture; 65% Class “A” and 35% Pozmix:

(iii) Determine density and yield of final slurry: Problem (iii) Determine density and yield of final slurry:

Problem