# US 2023/0054645 A1 · Dhsv scale removal method in the production string

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- Number: US 2023/0054645 A1
- Document ID: US20230054645A1
- Status: Published application
- Kind: A1
- Application number: 17/890,340
- Filed: 2022-08-18
- Published: 2023-02-23
- Earliest claimed: 2021-08-18
- Assignees: Petroleo Brasileiro S.A. - Petrobras
- Applicants: Petróleo Brasileiro S.A. - Petrobras
- Inventors: Mario Germino Ferreira Da Silva; Giselle Maria Lopes Leite Da Silva; Tiago Cavalcante Freitas; Rosane Alves Fontes; Fernando Antonio Moreira Da Silva
- Web page: https://patentgrep.com/patent/US20230054645A1

## CPC

- C01D 1/22: with carbonates or bicarbonates
- E21B 37/06: using chemical means for preventing or limiting {, e.g. eliminating,} the deposition of paraffins or like substances
- C01F 11/18: Carbonates
- E21B 41/02: in situ inhibition of corrosion in boreholes or wells
- C01C 1/26: Carbonates or bicarbonates of ammonium
- C01D: COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides C01B17/22; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia and cyanogen, containing nitrogen and other non-metals C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; phosphides C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- C01F: COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; sulfides or polysulfides of magnesium, calcium, strontium, or barium C01B17/42; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds other than ammonia or cyanogen containing nitrogen and non-metals and optionally metals C01B21/082; amides or imides of silicon C01B21/087}; metal {imides or} amides C01B21/092, {C01B21/0923}; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanic acid C01C3/14; salts of cyanamide C01C3/16; thiocyanates C01C3/20; {double sulfates of magnesium with sodium or potassium C01D5/12; with other alkali metals C01D15/00, C01D17/00})
- C01C: AMMONIA; CYANOGEN; COMPOUNDS THEREOF ({metal hydrides, monoborane, diborane or addition complexes thereof C01B6/00}; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; azides C01B21/08; {compounds other than ammonia or cyanogen, containing nitrogen, non-metals and optionally metals C01B21/082}; metal imides or amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; compounds containing silicon C01B33/00; compounds containing boron C01B35/00)

## Abstract

The present invention addresses to a method of removing scale from the DHSV of the oil production string aiming at maintaining the production of the wells and thus avoiding the loss of production. First, a neutralizing solution is placed in the service line, before pumping the scale removing solution through the string to act on the DHSV. Next, the acid is pumped into the production string to react with the calcium carbonate scale. After the time for the dissolution of the scale inside the DHSV, the well is opened for production by the service line. The spent acid is mixed with the neutralizing solution inside the service line, reducing its corrosiveness in relation to the service line, contributing to its preservation.

## Claims

### Claim at position 1

1- A DHSV SCALE REMOVAL METHOD IN THE PRODUCTION STRING, characterized in that it comprises the following steps:
(1) Opening the WCT valve that gives access from the production line to the interior of the production string;
(2) Pumping a 1st diesel spacer cushion;
(3) Pumping an alkalizer cushion in a volume 1.5 times the volume of acid that will be pumped;
(4) Pumping a 2nd diesel spacer cushion with a volume equal to that of the 1st diesel cushion;
(5) Pumping the DBX (diesel, butyl glycol and xylene) cushion;
(6) Pumping with completion fluid to displace the front of the 1st diesel spacer cushion to the WCT, then stopping pumping;
(7) Closing the WCT valve that gives access to the string;
(8) Opening the WCT valve that gives access to the lift gas line;
(9) Pumping, placing the 1st diesel spacer cushion, the entire alkalizer cushion and the 2nd diesel cushion to the interior of the gas lift line, in order to leave the interior of the WCT with diesel;
(10) Closing the WCT valve that gives access to the lift gas line;
(11) Opening the WCT valve that gives access to the production string;
(12) Pumping a cushion of DBX (diesel, butyl glycol and xylene) and the acid to the interior of the production string up to the DHSV;
(13) Waiting for the contact time between 30 minutes and 1 hour for the CaCO3 removal reaction;
(14) Opening the WCT valve that gives access to the lift gas line;
(15) Opening the well for cleaning and simultaneously pumping, through the lift gas line, the (alkaline) neutralizing solution to neutralize the acid that will be produced by the well, mixed with the oil.

### Claim at position 2 (depends on 1)

2- THE METHOD according to claim 1, characterized in that the alkalizer cushion consists of caustic soda and/or sodium bicarbonate.

### Claim at position 3 (depends on 1)

3- THE METHOD according to claim 1, characterized in that the acid is chosen from organic or mineral acids, such as 7% formic acid, 10% acetic acid and/or 15% hydrochloric acid.

### Claim at position 4 (depends on 1)

4- THE METHOD according to claim 1, characterized in that the neutralizing solution consists of caustic soda, sodium bicarbonate or ammonium carbonate.