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1. WO2020014109 - PROCÉDÉ DE TRAITEMENT DE REFLUX DE FRACTURATION ET D'EAU PRODUITE COMPRENANT UNE MATIÈRE RADIOACTIVE NATURELLE

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

CLAIMS

What is claimed is:

1. A method of treating frac flowback containing barium, naturally occurring radioactive material (NORM) and hardness employing a dual stage precipitation process to reduce or minimize the production of sludge containing NORM, the method comprising:

A. in a first stage precipitation process:

i. mixing a sulfate source with the frac flowback in a barium sulfate-NORM reaction tank and precipitating barium sulfate and NORM;

ii. after mixing the sulfate source with the frac flowback, subjecting the frac flowback to a solids-liquid separation process to produce a first effluent and a first sludge containing the barium sulfate and NORM;

B. in a second stage precipitation process:

i. adding an alkaline reagent to the first effluent and increasing the pH of the effluent;

ii. chemically softening the effluent by precipitating hardness; iii. after precipitating the hardness, subjecting the first effluent to a solids- liquid separation process and producing a second effluent and a second sludge containing the hardness;

C. recycling the first sludge containing the barium sulfate and NORM and mixing the first sludge with the frac flowback and the sulfate source; and

D. recycling a sufficient amount of the first sludge to maintain the NORM

concentration in the second sludge at or below a threshold level.

2. The method of claim 1 wherein the first stage precipitation process is carried in the absence of barium being added to the frac flowback.

3. The method of claim 1 wherein the first sludge is recycled at a rate (weight of sludge recycle/weight of sludge generated) of 100:1 or greater.

4. The method of claim 1 wherein recycling a sufficient amount of the first sludge includes recycling about 5 to 20 parts of barium sulfate (dry basis) to 1 part of precipitated barium sulfate.

5. The method of claim 1 wherein in the first stage precipitation process, the sulfate source is mixed with frac flowback in a barium-NORM reaction tank; and the method includes maintaining the concentration of the first sludge in the barium-NORM reaction tank between

about 10 g/L and 100 g/L so as to precipitate a majority of the NORM in the first stage precipitation process.

6. The method of claim 1 including recycling an amount of the first sludge that yields a residual sulfate concentration of less than 100 mg/L.

7. The method of claim 1 including recycling a sufficient amount of the first sludge to maintain the concentration of NORM in the second sludge below a threshold limit of

25 pCi/wet g.

8. A method of treating frac flowback containing barium, strontium, hardness and naturally occurring radioactive material (NORM) and employing a dual stage precipitation process to reduce or minimize the production of sludge containing NORM, the method comprising:

A. in a first stage precipitation process:

i. mixing a sulfate source with the frac flowback in a barium sulfate-NORM reaction tank and precipitating barium sulfate and NORM;

ii. after mixing the sulfate source with the frac flowback, subjecting the frac flowback to a solids-liquid separation process to produce a first effluent and a first sludge containing the barium sulfate and NORM;

B. in a second stage precipitation process:

i. adding an alkaline reagent to the first effluent in a reaction tank and increasing the pH of the first effluent;

ii. chemically softening the first effluent by precipitating hardness;

iii. after precipitating the hardness, subjecting the first effluent to a solids- liquid separation process and producing a second effluent and a second sludge containing the hardness;

C. recycling the first sludge containing the barium sulfate and NORM and mixing the first sludge with the frac flowback and the sulfate source; and

D. recycling a sufficient amount of the first sludge to maintain the NORM

concentration in the second sludge at or below a threshold level.

E. recycling the second sludge to the second stage reaction tank to assist in the chemical precipitation of hardness.

F. adding a“ballast” to the second stage precipitation process to assist in the

settling of the solids.

G. adding soda ash (sodium carbonate) or other carbonate sources to the second stage precipitation process to assist in the precipitation of calcium carbonate and/or strontium carbonate.