“Down and Dirty“ Field Scale Analysis

1. “Down and Dirty“ Field Scale Analysis • This is a procedure used when the Account Representative or the field Technician is called upon to identify scale samples in the field. An operator may need to take immediate steps to remove scale from production tubing, flow lines, or other pieces of equipment, and time does not permit submitting the sample scale to a laboratory for analysis. The PCC personnel must be able to determine where the scale is calcium carbonate, iron carbonate, calcium sulfate, barium sulfate, strontium sulfate, or a combination of scales. The following procedure outlines various methods that the personnel in the field may use to determine the type of scale in question. At the very least, this method of identification will give a reasonable basis for recommending a removal treatment. • Prior to subjecting any scale sample to an analytical procedure, the sample should be rinsed in a solution of xylene to remove any oil coating. • Check with magnet to determine if any iron is in the solids. (Strongly magnetic? Slightly magnetic, Not magnetic) If magnetic, then you already know that it is some type of iron compound. • Put solid in water. If it dissolves, it’s salt (NaCl). If not, got to step 3. • Put solid in 15% HCl. If it violently effervesces (like Alka-Seltzer) with no odor and does not appreciably turn the acid yellowish/greenish, it’s Calcium Carbonate (CaCO3) scale. If not, go to step 4. • If it violently effervesces (like Alka-Seltzer), turns the acid yellowish/greenish, gives off “rotten egg” odor, it’s Iron Sulfide (FeS). If it slowly efferveseces, turns slightly yellowish/greenish, gives off slight “rotten egg” odor, turns white while effervescing, it’s Iron Carbonate (FeCaCO3). If not, go to step 6. NOTE: IRON CARBONATE SCALE IS A CORRROSION BY-PRODUCT OF CO2 AND WILL ALWAYS HAVE UNDER-DEPOSIT PITTING! • Put solid sample in scale converter. After some time, if it turns into “cottage cheese”, add 15% HCl. If it solubilizes, it’s Calcium Sulfate (CaSO4) scale. • If still no reaction, put solid into solvent. If it solubilizes, it’s hydrocarbon (paraffin, asphaltene). (If it burns with lighter, it’s hydrocarbon. • If no response from previous steps, the solid is either inert (sand, silica, clay) or Barium Sulfate (BaSO4) or Strontium Sulfate (SrSO4) scale…get to lab.

2. Soluble in water = salt (NaCl)

3. Not soluble in water BUT, when exposed to acid = Violent reaction with HCl = CaCO3

4. No reaction with water or HCl Scale converter turns it into an acid soluble sludge HCl solubilizes acid soluble sludge, i.e. converted scale = CaSO4

5. Scale Scale in Heavy Sludge Sludge Coated Scale in 15% HCL + Micel Approximately 10Seconds Later Micel solvents, such as PCC Acid Booster, prevents acid emulsions, removes hydrocarbons from acid soluble material, prevents sludge, increases permeability, leaves formation rock “water wet”

8. Scaling Tendency Calculations Calcium Carbonate: Multiply mg/liter of Bicarbonate by the mg/liter of Calcium If the resulting product is: Below 500,000 Tendency Remote Above 500,000 Tendency Possible Above 1,000,000 Tendency Probable Calcium Sulfate (Gypsum): Multiply mg/liter of Sulfate by the me/liter of Calcium Below 5,000,000 Tendency Remote 5,000,000 to 10,000,000 Tendency Possible Above 10,000,000 Tendency Probable

9. The components marked with an (*) are essential to obtaining a thorough and meaningful water analysis. Table 2 Relative Solubilities of Mineral Scales in Water Table 1 Primary Constituents of Oilfield Waters Table 3 Primary Variables in the Formation of Mineral Scales

10. Figure 1 - Representative Water Analysis Indicating Scaling Tendencies Table 4 Common Suspended Solids and their Probable Origins

11. Figure 3 - Calcium Sulfate Scale Figure 4 - Barium Sulfate Scale Figure 2 - Calcium Carbonate Scale