Method of removing calcium-containing water-based filter cake using a biodegradable acid solution

Patent metadata

Field	Value
Publication number	US-11566161-B2
Application number	US-202016733495-A
Country	US
Kind code	B2
Filing date	Jan 3, 2020
Priority date	Jan 3, 2020
Publication date	Jan 31, 2023
Grant date	Jan 31, 2023

Abstract

A method of removing calcium-containing water-based filter cake from a wellbore involving contacting the calcium-containing filter cake with a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, and a surfactant. The method is performed at a pressure of 200 to 400 psi and a temperature of 50 to 125° C. The method removes calcium-containing filter cake made of water, calcium carbonate, a polymer or starch and a clay. The method meets industry standard steel corrosion rates of less than 0.049 lb/ft 2 per day. Also disclosed is a biodegradable acid solution of water, hydrochloric acid, formic acid, citric acid, and a surfactant that meets OECD 301B thresholds for ready biodegradability.

First claim

The invention claimed is:

1. A method for removing a calcium-containing filter cake from a wellbore, the method comprising:
contacting the calcium-containing filter cake with a biodegradable acid solution comprising
69.5 to 93.375 wt % of water,
5 to 20 wt % of hydrochloric acid,
0.75 to 3.5 wt % of formic acid,
0.75 to 3.5 wt % of citric acid, and
0.0075 to 0.75 wt % of a surfactant, each based on a total weight of the biodegradable acid solution,
wherein the biodegradable acid solution is contacted with the calcium-containing filter cake at a pressure of 200 to 400 psi, and
wherein the calcium-containing filter cake comprises water, calcium carbonate, a polymer or starch, and a clay.

2. The method of claim 1 , wherein the biodegradable acid solution has a density of 0.90 to 1.25 g/cm 3 at 20 to 30° C.

3. The method of claim 1 , wherein the biodegradable acid solution has a viscosity of 1.5 to 1.7 cP at 20 to 30° C.

4. The method of claim 1 , wherein the biodegradable acid solution has a surface tension of 30 to 33 mN/m at 20 to 30° C.

5. The method of claim 1 , wherein the biodegradable acid solution has a pH of −1.5 to −1.1 at 20 to 30° C.

6. The method of claim 1 , wherein the calcium-containing filter cake is substantially free of an oil.

7. The method of claim 1 , wherein the contacting is performed at a temperature of 50 to 125° C.

8. The method of claim 1 , wherein the contacting is performed for 1 to 48 hours.

9. The method of claim 1 , wherein a volume ratio of the biodegradable acid solution to the calcium-containing filter cake being contacted is 5:1 to 50:1.

10. The method of claim 1 , wherein greater than 92.5% of a volume of the calcium-containing filter cake is removed.

11. The method of claim 1 , wherein removing the calcium-containing filter cake from the wellbore increases the permeability of the wellbore by 90 to 100%.

12. The method of claim 1 , wherein the method removes the calcium-containing filter cake while causing a corrosion rate of steel of less than 0.049 lb/ft 2 per day at 50 to 125° C.

13. The method of claim 1 , wherein the biodegradable acid solution reaches a plateau of 75 to 99% of theoretical CO 2 by day 40 according to OECD 301B biodegradation test.

14. The method of claim 1 , wherein the surfactant is sodium dodecyl sulfate.

15. The method of claim 1 , wherein the biodegradable acid solution consists of:
69.5 to 93.375 wt % of water,
5 to 20 wt % of hydrochloric acid,
0.75 to 3.5 wt % of formic acid,
0.75 to 3.5 wt % of citric acid, and
0.0075 to 0.75 wt % of a surfactant, each based on a total weight of the biodegradable acid solution.

16. The method of claim 1 , wherein the biodegradable acid solution comprises:
84.75 to 86.75 wt % of water,
10 wt % of hydrochloric acid,
1.5 to 2.5 wt % of formic acid,
1.5 to 2.5 wt % of citric acid, and
0.25 wt % of a surfactant, each based on a total weight of the biodegradable acid solution.

17. The method of claim 16 , wherein the surfactant is sodium dodecyl sulfate.

18. The method of claim 1 , wherein the biodegradable acid solution is devoid of hydrofluoric acid.

19. The method of claim 1 , wherein the method causes a permeability decrease of no greater than 6% of an initial permeability of a wellbore limestone when performed at 100° C., with a differential pressure of 300 psi, and with a contact time of 6 to 20 hours.

Assignees

• Univ King Fahd Pet & Minerals

Inventors

• Elkatatny Salaheldin
• MAHMOUD Mohamed
• Sultan Abdullah

Classifications

• C09K8/035

  Organic additives · CPC title

• C09K2208/06

  Structured surfactants, i.e. well drilling or treating fluids with a lamellar or spherulitic phase · CPC title

• C09K8/524 Primary

  organic depositions, e.g. paraffins or asphaltenes · CPC title

• C09K8/528 Primary

  inorganic depositions, e.g. sulfates or carbonates · CPC title

• C09K8/032

  Inorganic additives · CPC title