1. A method of cementing in a subterranean formation comprising:
introducing a cement composition into a wellbore penetrating the subterranean formation,
wherein at least a portion of the subterranean formation has a temperature less than or equal to the freezing point of an aqueous liquid, and
wherein the cement composition comprises:
(A) cement;
(B) water; and
(C) a pozzolan,
wherein the cement composition has a heat of hydration of less than 50 BTU per pound; and
causing or allowing the cement composition to set in the wellbore after the step of introducing.
2. The method according to claim 1, wherein the subterranean formation is located off-shore or in a permafrost region.
3. The method according to claim 1, wherein the subterranean formation contains a gas hydrate deposit.
4. The method according to claim 3, wherein gas hydrates are present in or adjacent to, a portion of the wellbore.
5. The method according to claim 1, wherein the cement is selected from the group consisting of Portland cements, gypsum cements, high alumina content cements, slag cements, high magnesia content cements, and combinations thereof.
6. The method according to claim 1, wherein the water is selected from the group consisting of freshwater, brackish water, saltwater, and any combination thereof.
7. The method according to claim 1, wherein the pozzolan comprises the compounds silicon dioxide, aluminum oxide, and calcium oxide.
8. The method according to claim 1, wherein the pozzolan further comprises iron III oxide, and wherein the silicon dioxide, iron III oxide, aluminum oxide comprise at least 70% of the total chemical composition of the pozzolan.
9. The method according to claim 1, wherein the pozzolan is ground granulated blast furnace slag.
10. The method according to claim 1, wherein the pozzolan comprises calcium oxide and wherein the concentration of calcium oxide in the pozzolan is equal to or less than the concentration necessary for the cement composition to have a heat of hydration less than 50 BTU per pound.
11. The method according to claim 10, wherein the concentration of calcium oxide in the pozzolan is equal to or less than the concentration necessary for the cement composition to have a heat of hydration less than 40 BTU per pound.
12. The method according to claim 1, wherein the pozzolan has a calcium oxide concentration of less than 15% by weight of the pozzolan.
13. The method according to claim 1, wherein the pozzolan has a calcium oxide concentration of less than 5% by weight of the pozzolan.
14. The method according to claim 10, wherein the concentration of calcium oxide is less than or equal to the concentration necessary such that the gas hydrates are not de-stabilized.
15. The method according to claim 1, wherein the particle size of the pozzolan is selected such that a mixture consisting essentially of the cement, the water, and the pozzolan develops a compressive strength of at least 500 psi at a time of 48 hours, a temperature of 100\xb0 F., and a pressure of 3,000 psi.
16. The method according to claim 1, wherein the cement composition develops a compressive strength of at least 500 psi at a time of 48 hours, a temperature of 100\xb0 F., and a pressure of 3,000 psi.
17. The method according to claim 1, wherein the pozzolan is in a concentration of at least 30% by weight of the cement.
18. The method according to claim 1, wherein the concentration of the pozzolan is selected such that the cement composition has a heat of hydration of less than 50 BTU per pound.
19. The method according to claim 1, wherein the concentration of the pozzolan is greater than or equal to the necessary concentration such that the gas hydrates are not de-stabilized.
20. The method according to claim 1, wherein the concentration of the pozzolan is greater than or equal to the necessary concentration such that the aqueous liquid in a solid state does not melt into a liquid state.
21. A method of cementing in a subterranean formation comprising:
introducing a cement composition into a wellbore penetrating the subterranean formation,
wherein at least a portion of the subterranean formation has a temperature less than or equal to the freezing point of an aqueous liquid, and
wherein the cement composition comprises:
(A) cement;
(B) water; and
(C) a pozzolan, wherein the pozzolan has a calcium oxide concentration of less than 15% by weight of the pozzolan, and wherein the pozzolan has a concentration of at least 15% by weight of the cement,
wherein the cement composition has a heat of hydration of less than 50 BTU per pound; and
causing or allowing the cement composition to set in the wellbore after the step of introducing.
22. The method according to claim 21, wherein the pozzolan has a calcium oxide concentration of less than 5% by weight of the pozzolan.
23. The method according to claim 21, wherein the concentration of the pozzolan is greater than or equal to the necessary concentration such that the aqueous liquid in a solid state does not melt into a liquid state.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical element comprising:
an electromotive force-generating element that generates an electromotive force in response to electromagnetic wave; and
an optical density-changing element that changes its optical density according to the electromotive force,
the optical density-changing element comprising:
at least one of metal sulfide and metal nitride; and
a material that causes a change of the optical density and adsorbs to said at least one of metal sulfide and metal nitride.
2. The optical element according to claim 1, wherein the metal sulfide is zinc sulfide.
3. The optical element according to claim 1, wherein the metal nitride is gallium nitride.
4. The optical element according to claim 1,
wherein the optical density-changing element comprises at least one of: a metal sulfide layer containing the metal sulfide; and a metal nitride layer containing the metal nitride,
and wherein said at least one of the metal sulfide layer and the metal nitride layer has a surface roughness factor of greater than 20.
5. The optical element according to claim 1, wherein the optical density-changing element further comprises a metal oxide layer including a material that causes a change of the optical density and adsorbs to the metal oxide layer.
6. The optical element according to claim 5, wherein the metal oxide layer has a surface roughness factor of greater than 20.
7. The optical element according to claim 5, wherein metal oxide of the metal oxide layer is tin oxide.
8. The optical element according to claim 5, wherein metal oxide of the metal oxide layer is antimony-doped tin oxide.
9. The optical element according to claim 1, wherein the electromotive force-generating element and the optical density-changing element are disposed apart from each other.
10. The optical element according to claim 1, wherein the electromagnetic wave is at least one of ultraviolet ray and visible light.
11. The optical element according to claim 1, wherein the electromotive force-generating element comprises a light-receiving element including semiconductor.
12. The optical element according to claim 1, wherein the electromotive force-generating element comprises a light-receiving element including at least one of silicon, titanium oxide, zinc oxide and tin oxide.
13. The optical element according to claim 1, wherein the optical density-changing element absorbs visible light in a colored state.
14. The optical element according to claim 1, wherein the optical density-changing element absorbs a plurality of visible light rays having different wavelengths in a colored state.
15. The optical element according to claim 1, wherein the optical density-changing element absorbs blue light, green light and red light in a colored state.
16. The optical element according to claim 1, wherein the optical density-changing element has a neutral gray absorption characteristic in a colored state.
17. The optical element according to claim 1, wherein the optical density-changing element exhibits an optical density of 0.2 or less at a wavelength \u03bb of 400 nm in a decolored state.
18. The optical element according to claim 1, wherein the optical density-changing element exhibits an average optical density of 0.125 or less in a wavelength \u03bb of from 400 nm to 500 nm, an average optical density of 0.125 or less in a wavelength \u03bb of from 500 nm to 600 nm, and an average optical density of 0.125 or less in a wavelength \u03bb of from 600 nm to 700 nm, in a decolored state.
19. The optical element according to claim 1, wherein the optical density-changing element has an antireflection layer.
20. The optical element according to claim 1, wherein the optical density-changing element further comprises a compound which undergoes coloring due to at least one of oxidation and reduction.
21. The optical element according to claim 1, wherein the optical density-changing element is uniform all over a surface of the optical density-changing element.
22. The optical element according to claim 1, wherein the optical density-changing element constitutes each of a plurality of segments, said plurality of segments constituting a display element.
23. The optical element according to claim 1, wherein the optical density-changing element exhibits an optical density of 0.5 or more on the average at \u03bb of from 400 nm to 700 nm during response to radiation of the electromagnetic wave.
24. The optical element according to claim 1, wherein a response time of change of the optical density with respect to the electromagnetic wave is 5 seconds or less.
25. A camera unit comprising an optical element according to claim 1.
26. The camera unit according to claim 25, wherein the optical density-changing element is disposed on an optical axis of a lens.
27. The camera unit according to claim 26, which is a film unit with lens.