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“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.

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Presentation on theme: "“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."— Presentation transcript:

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. 1.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. 2.Put solid in water. If it dissolves, it’s salt (NaCl). If not, got to step 3. 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. 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! 5.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. 6.If still no reaction, put solid into solvent. If it solubilizes, it’s hydrocarbon (paraffin, asphaltene). (If it burns with lighter, it’s hydrocarbon. 7.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 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” ScaleScale in Heavy Sludge Sludge Coated Scale in 15% HCL + Micel Approximately 10 Seconds Later

6 QUALITATIVE ANALYSIS OF SOLIDS Soluble in HCL Component Soluble in SolventMagneticReactionAcid ColorSmell Water Soluble HydrocarbonsYesNoNone No CaCO3No ViolentNone No CaSO4No None No BaSO4, SrSO4No None No FeSNoWeakStrongYellowH2S No Fe2O3No WeakYellowNone No Fe3O4NoStrongWeakYellowNone No FeCO3No V StrongYellowNone No NaClNo None Yes Sand, Silt, ClayNo None No

7 QUALITATIVE ANALYSIS OF SOLIDS Soluble in HCL ComponentSoluble in SolventMagneticReactionAcid ColorSmellWater Soluble HydrocarbonsYesNoNone No CaCO3No ViolentNone No CaSO4No None No BaSO4, SrSO4No None No FeSNoWeakStrongYellowH2SNo Fe2O3No WeakYellowNoneNo Fe3O4NoStrongWeakYellowNoneNo FeCO3No V StrongYellowNoneNo NaClNo None Yes Sand, Silt, ClayNo None No HydrocarbonsParaffin; Asphaltenes CaCO3Calcium Carbonate; Calcite CaSO4Calcium Sulfate; Anhydrite; Gypsum BaSO4, SrSO4Barium Sulfate, Barite; Strontium Sulfate, Celestite FeSIron Sulfide Fe2O3Iron Oxide Fe3O4Iron Hydroxide FeCO3Iron Carbonate NaClSalt Sand, Silt, ClayInerts

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

9 CationsAnionsOther Properties *Calcium (Ca)*Chloride (Cl)*pH *Magnesium (Mg)*Carbonate (CO 3 )*Temperature *Sodium (Na)*Bicarbonate (HCO 3 )*Specific Gravity *Iron (Fe)*Sulfate (SO 4 )*Dissolved Carbon Dioxide *Barium (Ba) *Sulfide as H 2 S Strontium (Sr) Resistivity Manganese (Mn) Dissolved Oxygen Bacterial Population Oil Content Turbidity Suspended Solids – amount, size, shape, chemical composition The components marked with an (*) are essential to obtaining a thorough and meaningful water analysis. Table 2 Relative Solubilities of Mineral Scales in Water Mineral ScaleSolubility (mg/L) in Water Calcium Sulfate (Gypsum) - - CaSO 4. 2H 2 O2080 mg Calcium carbonate - - CaCO 3 53 mg Barium Sulfate - - BaSO mg Table 1 Primary Constituents of Oilfield Waters Table 3 Primary Variables in the Formation of Mineral Scales Scale, or DepositChemical FormulaPrimary Variables Calcium CarbonateCaCO 3 -Partial pressure of CO 2 (scale increases as CO 2 decreases) -Less Soluble with Increasing temperature -Pressure Drops -More soluble as TDS increases Calcium Sulfate CaSO 4. 2H 2 0 (dehydrate) CaSO 4 (anhydrite) -Less Soluble with Increasing temperature -Pressure drops -More soluble as TDS increases Barium Sulfate Strontium Sulfate BaSO 4 SrSO 4 -More soluble as Temperatures increase -More soluble as TDS increases Iron Compounds: Iron Carbonate Iron Sulfide Iron (II) Hydroxide Iron (III) Hydroxide Iron Oxide FeCO 3 FeS Fe(OH) 2 Fe(OH) 3 Fe 2 O 3 -Corrosion by-products -Bacterial activity -Dissolved gases -Depositions increase as pH increases (especially true after an acid job with spent acids)

10 TypeHydrocarbons Iron Compounds CarbonatesSulfatesInsolubles/organics -Oil Carry Over-Iron sulfide-Calcium -Formation fines -Paraffin-Iron oxidecarbonatesulfate-Sand DetailDeposition-Iron carbonate-Iron carbonate - Magnesium carbonate -Magnesium sulfate -Barium sulfate -Microbes - Asphaltenes -Separator-Corrosion-Scaling waters-Scaling water-Inadequate wellbore malfunction-Incompatible-Corrosion-Highcleanouts -Truck treatingwaters-Pressure dropstemperature-Pump intakes set schedules-Oxygen-Fluid property-Pumplow Probable-Surface tankintroductionchangesoutlets/shrouds-Bacterial activity Origindamages -Improper equipment sizing -Stimulation by- products -Incompatible waters -Natural, or induced, formation of asphaltenes (CO 2 flood) 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


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