Corrosion and erosion-resistant wellhousing

A process for cementing a well housing in a subterranean formation containing corrosive geothermal brines penetrated by a wellbore, the process comprising:

• (a) positioning an outer well casing into said wellbore so that a first annulus is formed between the inner surface of the wellbore and the outer surface of the outer well casing;
• (b) filling the first annulus with a hardenable cement slurry;
• (c) allowing the slurry to harden and form in the first annulus an outer cement liner substantially continuous and impermeable to said corrosive geothermal brines;
• (d) positioning an inner well casing into the wellbore so that a second annulus is formed between the outer surface of the inner well casing and the inner surface of the outer well casing;
• (e) filling the second annulus with a hardenable cement slurry;
• and
• (f) allowing the slurry in the second annulus to harden and form a cement liner substantially continuous and impermeable to the corrosive geothermal brine.

A process for cementing a corrosion-resistant wellhousing in a subterranean formation which contains corrosive fluids, the process comprising:

• (a) drilling a wellbore into the formation;
• (b) positioning within the wellbore an outer metal well casing so that a first annulus is formed between the inner surface of the wellbore and the outer surface of the outer well casing;
• (c) filling the first annulus with a hardenable cement slurry;
• (d) allowing the slurry to harden into a substantially continuous, impermeable, thermally stable outer liner of cement in the first annulus, the inner surface of the outer liner lying along the outer surface of the outer well casing so as to form a substantially impermeable barrier to the corrosive fluids of the subterranean formation;
• (e) positioning an inner metal well casing into the wellbore, the inner well casing having a diameter smaller than the diameter of the outer well casing so that a second annulus is formed between the outer surface of the inner well casing and the inner surface of the outer well casing;
• (f) filling the second annulus with a hardenable cement slurry;
• (g) allowing the slurry in the second annulus to harden into a substantially continuous, substantially impermeable inner cement liner, the outer surface of the inner liner lying along the inner surface of the outer well casing so as to form a substantially impermeable barrier to the corrosive fluids of the subterranean formation;
• and
• (h) producing well fluids comprising the corrosive fluids through the inner metal casing until the inner metal casing is substantially corroded away without substantial corrosion to the outer casing.

An apparatus for producing fluids from a wellbore penetrating a subterranean formation wherein the apparatus comprises:

• (a) a metal casing positioned within the wellbore;
• (b) a first cement liner comprised of a hardened, substantially continuous layer of cement having permeability of not more than about 1 millidarcy, which first cement liner lies along the outer surface of the metal casing;
• and
• (c) a second cement liner comprised of a hardened, substantially continuous layer of cement having permeability of not more than about 1 millidarcy, which second cement liner lies along the inner surface of the metal casing.

An apparatus for producing geothermal fluids from a wellbore penetrating a subterranean formation wherein the apparatus comprises:

• (a) a metal casing positioned within the wellbore;
• (b) a first substantially continuous cement liner comprised of a hardened layer of cement substantially impermeable to the geothermal fluids positioned between the metal casing and the wellbore;
• and
• (c) a second substantially continuous cement liner comprised of a hardened layer of cement substantially impermeable to the geothermal fluids is positioned within the metal casing with the outside surface of the second cement liner in contact with the inside surface of the metal casing.

An apparatus for producing corrosive fluids from a wellbore penetrating a subterranean formation containing corrosive fluids wherein the apparatus comprises:

• (a) an outer well casing positioned within the wellbore;
• (b) a first cement liner comprised of a hardened substantially continuous layer of cement substantially impermeable to said corrosive fluids, which first cement liner lies along the outer surface of the outer well casing;
• (c) an inner well casing positioned within the wellbore and further within the bore of the outer well casing located therein;
• and
• (d) a second cement liner comprised of a hardened substantially continuous layer of cement substantially impermeable to said corrosive fluids, which second cement liner lies along the inner surface of the outer well casing.

An apparatus comprising:

• (1) an essentially tubular metal casing;
• (2) an essentially tubular, continuous first concrete layer having permeability of not more than about 1 millidarcy surrounding and in contact with the outer surface of said metal casing;
• and
• (3) an essentially tubular, continuous second concrete layer having permeability of not more than about 1 millidarcy in contact with the inner surface of the metal casing.

An apparatus comprising:

• (1) an essentially tubular metal casing;
• (2) an essentially continuous, tubular first concrete layer substantially impenetrable to geothermal brines, said layer surrounding and being in contact with the outer surface of said metal casing;
• and
• (3) an essentially continuous, tubular second concrete layer substantially impenetrable to geothermal brines, said layer being in contact with inner surface of the metal casing.