Coal slag solidification of drilling fluid

• US 5,439,056 A
• Filed: 06/28/1993
• Issued: 08/08/1995
• Est. Priority Date: 06/28/1993
• Status: Expired due to Term

• Current Assignee: Shell Oil Company (Shell Plc)
• Original Assignee: Shell Oil Company (Shell Plc)
• Inventors: Cowan, Kenneth M.
• Primary Examiner(s): Suchfield, George A.
• Application Number:
  US08/084,660
• Time in Patent Office: 771 Days
• Field of Search: 166/292, 166/293, 106/767, 106/789, 106/790, 106/791, 175/65, 507/140
• US Class Current: 166/293
• CPC Class Codes: C04B 18/049 Wastes from oil or other wells, e.g. drilling mud
• CPC Class Codes: C04B 18/067 Slags
• CPC Class Codes: C04B 24/18 Lignin sulfonic acid or derivatives thereof, e.g. sulfite lye
• CPC Class Codes: C04B 28/021 Ash cements, e.g. fly ash cements fly ash as filler C04B18/08; Cements based on incineration residues, e.g. alkali-activated slags from waste incineration alkali-activated combustion residues as such C04B7/243; mixtures of the lime-pozzuolane type C04B28/18; Kiln dust cements
• CPC Class Codes: C04B 28/18 containing mixtures of the silica-lime type
• CPC Class Codes: C09K 8/16 characterised by the inorganic compounds other than clay
• CPC Class Codes: C09K 8/46 containing inorganic binders, e.g. Portland cement
• CPC Class Codes: E21B 33/13 Methods or devices for cementing, for plugging holes, crevices or the like
• CPC Class Codes: Y02W 30/91 Use of waste materials as fillers for mortars or concrete

Abstract

Drilling fluid is solidified by the incorporation therein of coal slag. In a preferred embodiment lime is also incorporated into said drilling fluid and/or said drilling fluid is a lime drilling fluid. Thus, there is provided a cementitious composition comprising drilling fluid, coal slag and, generally, lime.

Claims

1. A method for solidifying a drilling fluid in a borehole, said drilling fluid being a lime mud or a non-lime mud which is converted to a lime mud by addition of lime, comprising:

admixing coal slag with said drilling fluid to produce a cementitious slurry;

displacing said cementitious slurry into said borehole; and

allowing said cementitious slurry to solidify in situ.

2. A method according to claim 1 wherein said non-lime mud is converted to a lime mud by addition of lime and a viscosity reducer prior to the addition of said coal slag.

3. A method according to claim 1 wherein 10 to 50 lbs/bbl of lime is also incorporated into said drilling fluid in producing said cementitious slurry.

4. A method according to claim 3 wherein said coal slag is incorporated into said cementitious slurry in an amount within the range of 100 to 500 lbs/bbl of said cementitious slurry.

5. A method according to claim 1 wherein said coal slag is incorporated into said drilling fluid in an amount sufficient to give 100 to 500 lbs/bbl of said cementitious slurry.

6. A method according to claim 1 wherein said coal slag is introduced in an amount sufficient to give 150 to 300 lbs/bbl of said cementitious slurry.

7. A method according to claim 1 wherein said lime constitutes the only activator added to said drilling fluid and wherein said lime is added in the form of calcium hydroxide.

8. A method according to claim 1 wherein said coal slag is a quenched slag from the carbonization of coal.

9. A method according to claim 1 wherein said coal slag has a particle size such that it exhibits a Blaine specific surface area within the range of 4,000 to 9,000 cm² /g.

10. A method according to claim 1 wherein a lignosulfonate viscosity reducing agent is added to said drilling fluid in said production of said cementitious slurry.

11. A method according to claim 1 wherein said cementitious slurry contains in addition a component selected from Portland cement, blast furnace slag and fly ash.

12. A method according to claim 11 wherein said coal slag is quenched coal slag from the burning of coal in the production of heat and wherein said coal slag has a particle size such that it exhibits a Blaine specific surface area within the range of 4,000 to 9,000 cm² /g, said lime is added in the form of calcium hydroxide and in amount within the range of 10 to 40 lbs/bbl of said drilling fluid, and wherein said coal slag is added in an amount within the range of 150 to 300 lbs/bbl of said cementitious slurry.

13. A method according to claim 12 wherein said cementitious slurry is passed into direct fluid contact with drilling fluid in said borehole to displace said drilling fluid and wherein a displacement fluid in direct fluid contact with said cementitious slurry displaces said cementitious slurry into said annulus.