Pumpable geopolymer cement
This invention relates to an adaptable Geopolymer cement composition for application in oil and gas wells having a wide range of downhole temperatures. The base Geopolymer cement composition has an acceptable rheology of below 200 cP and can be tailored by the inclusion of various chemicals to control properties such as thickening time over a wide range of temperatures and densities. The disclosed Geopolymer cement composition is pumpable, mixable and stable. The composition can also be adapted to have expandable and swellable properties.
1. A pumpable geopolymer cement composition comprising:
an aluminosilicate source material;
an alkaline solution comprising a carrier fluid, an alkaline activator material and a silicate material, wherein, the weight:weight ratio of the alkaline solution:aluminosilicate source material is from 0.1 to 2:1, and the weight:weight ratio of the silicate material:alkaline solution is from 0.15 to 1:1,
wherein the composition further comprises a swellable material in an amount of from 10 to 60 wt % relative to the total weight of aluminosilicate source material in the composition.
2. The composition of claim 1 , wherein the aluminosilicate source material is fly ash type F.
3. The composition of claim 1 , wherein the alkaline solution comprises an alkaline activator material at a concentration of from 8 M to 12 M.
4. The composition of claim 1 , wherein the alkaline activator material is selected from one or more of sodium hydroxide and potassium hydroxide.
5. The composition of claim 1 , wherein the silicate material is a sodium silicate.
6. The composition of claim 1 , wherein the composition has a specific gravity of from 1.40 g/cm 3 to 1.91 g/cm 3 .
7. The composition of claim 1 , wherein the composition further comprises a weighting agent selected from one or more of the group consisting of barium sulfate, iron oxide, and manganese tetroxide, where the weighting agent is present in an amount of from 30 to 75 wt % relative to the total weight of aluminosilicate source material in the composition.
8. The composition of claim 7 , wherein the composition has a specific gravity of from 1.92 g/cm 3 to 2.99 g/cm 3 .
9. The composition of claim 1 , wherein the composition further comprises a lightweight material selected from one or more of the group consisting of silica-alumina microspheres, cenosphere, sodium-calcium-borosilicate in an amount of from 50 to 100 wt % relative to the total weight of aluminosilicate source material in the composition.
10. The composition of claim 9 , wherein the composition has a specific gravity of from 1.21 g/cm 3 to 1.55 g/cm 3 .
11. The composition of claim 1 , wherein the composition further comprises one or more of a defoamer, a fluid loss controller and a dispersant, where each, when present, is provided in a concentration of from 0.001 kg/L to 0.3 kg/L relative to the total volume of the composition.
12. The composition of claim 1 , wherein the composition further comprises a retarder material at a concentration of from 0.001 kg/L to 0.3 kg/L relative to the total volume of the composition.
13. The composition of claim 1 , wherein the composition further comprises a retarder material in an amount of from 5 to 60 wt % relative to the total weight of aluminosilicate source material in the composition.
14. The composition of claim 13 , wherein the retarder is a sugar or a sugar-substitute material.
15. The composition of claim 1 , wherein the composition further comprises a fast set material in an amount of from 25 to 45 wt % relative to the total weight of aluminosilicate source material in the composition.
16. The composition of claim 1 , wherein the composition further comprises an expanding material in an amount of from 2 to 10 wt % relative to the total weight of aluminosilicate source material in the composition.
17. A method of forming a pumpable geopolymer cement formulation comprising the steps of:
(a) mixing a carrier fluid with an alkaline activator material to form a first mixture;
(b) adding a silicate material to the first mixture of step (a) and mixing to form a second mixture; and
(c) adding an aluminosilicate material to the second mixture of step (b) and mixing,
wherein any one of steps (a) to (c) further comprises adding a swellable material in an amount of from 10 to 60 wt % relative to the total weight of aluminosilicate source material in the formulation.
18. The method of claim 17 , wherein one or both of the following apply:
one or more of a defoamer, a fluid loss controller and a dispersant are added and mixed into the first mixture of step (a) or the second mixture of step (b) and the resulting first or second mixture is then used in the subsequent step, where each of the defoamer, fluid loss controller and dispersant, when present, is provided in a concentration of from 0.001 kg/L to 0.1 kg/L relative to the total volume of the composition; and
(ii) a retarder material is added and mixed into the first mixture of step (a) or second mixture of step (b) and the resulting first or second mixture is then used in the subsequent step, where the retarder material is:
(I) provided in a concentration of from 0.001 kg/L to 0.3 kg/L relative to the total volume of the composition, optionally wherein the retarder material is lignosulfonate; or
(II) provided in an amount of from 5 to 60 wt % relative to the total weight of aluminosilicate source material in the composition, optionally wherein the retarder material is a sugar or a sugar-substitute material.
19. The method of claim 17 , wherein the mixing is conducted in line with the API RP10B-2 mixing procedure.