Well completion systems

Claim 2

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead into said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means at a downhole location within said protective casing and below the top of said permafrost zone for suspending a lower section of said production casing from said protective casing, stuffing box means at the wellhead for sealing the annulus between said production casing and said protective casing while allowing for relative longitudinal movement of said casings at the wellhead, a tubing string within said production casing, and surface support means at said wellhead for suspending said tubing string from said production string.

Claim 3

The system of claim 1 further comprising tubing support means at a depth at least as great as said first-named support means for suspending a lower section of said tubing from said production casing.

Claim 4

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead into said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means at a downhole location within said protective casing and below the top of said permafrost zone for suspending a lower section of said production casing from said protective casing, a surface casing within said well externally of said protective casing and penetrating said permafrost zone, and second support means for suspending a lower section of said protective casing in said surface casing at a subterranean location above said first-named support means.

Claim 5

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead into said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means at a downhole location within said protective casing and below the top of said permafrost zone for suspending a lower section of said production casing from said protective casing, a surface casing within said well externally of said protective casing and penetrating said permafrost zone, and second support means for suspending a lower section of said protective casing in said surface casing at a subterranean location above said first-named support means.

Claim 6

The system of claim 3 further comprising a cement sheath in the annulus surrounding said protective casing and extending from a location below said first-named support means to above said first-named support means, and a column of liquid in said annulus above said cement sheath, said liquid having a freezing temperature substantially below 32* F. to maintain it in a liquid state.

Claim 7

The system of claim 4 further comprising a cement sheath in the annulus surrounding said surface casing extending from a location below said second support means to above said second support means, and a column of liquid in said annulus above said cement sheath, said last-named liquid having a freezing temperature substantially below 32* F. to maintain it in a liquid state.

Claim 8

The system of claim 5 wherein said liquid in the annulus surrounding said surface casing comprises a thixotropic liquid.

Claim 9

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead through said permafrost zone to a location below said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means within said protective casing for suspending a lower section of said production casing from said protective casing at a location below said permafrost zone, a surface casing within said well externally of said protective casing, and second support means for suspending a lower section of said protective casing in said surface casing at a subterranean location above said first support means.

Claim 10

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead through said permafrost zone to a location below said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means within said protective casing for suspending a lower section of said production casing from said protective casing at a location below said permafrost zone, a surface casing within said well externally of said protective casing, and second support means for suspending a lower section of said protective casing in said surface casing at a subterranean location above said first support means.

Claim 11

Thy system of claim 7 further comprising stuffing box means at the wellhead for sealing the annulus between said production casing and said protective casing while allowing for relative longitudinal movement of said casing at the wellhead.

Claim 12

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead through said permafrost zone to a location below said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means within said protective casing for suspending a lower section of said production casing from said protective casing at a location below said permafrost zone, a surface casing within said well externally of said protective casing, second support means suspending a lower section of said protective casing in said surface casing at a subterranean location above said first support means, stuffing box means at the wellhead for sealing the annulus between said production casing and said protective casing while allowing for relative longitudinal movement of said casings at the wellhead, a tubing string within said production casing, and surface support means at said wellhead for suspending said tubing string from said production casing.

Claim 13

In a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the combination comprising: a protective casing within said well extending downwardly from the wellhead through said permafrost zone to a location below said permafrost zone, a production casing within said protective casing extending from the wellhead through said permafrost zone to the subterranean formation, support means within said protective casing for suspending a lower section of said production casing from said protective casing at a location below said permafrost zone, a surface casing within said well externally of said protective casing, second support means suspending a lower section of said protective casing in said surface casing at a subterranean location above said first support means, stuffing box means at the wellhead for sealing the annulus between said production casing and said protective casing while allowing for relative longitudinal movement of said casings at the wellhead, a tubing string within said production casing, and surface support means at said wellhead for suspending said tubing string from said production casing.

Claim 14

The system of claim 9 further comprising tubing support means at a depth at least as great as said first-named support means for suspending a lower section of said tubing from said production casing.

Claim 15

The system of claim 10 further comprising a cement sheath in the annulus surrounding said protective casing and extending from a location below said first-named support means to above said first-named support means, a column of liquid in said annulus above said cement sheath, a second cement sheath in the annulus surrounding said surface casing extending from a location below said second support means to above said second support means, and a column of liquid in said last-named annulus above said second cement sheath.

Claim 16

In a method of completing a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the steps comprising: a. locating within said well a surface casing which extends downwardly from the wellhead into said permafrost zone, b. locating within said well and within said surface casing a protective casing which extends downwardly from the wellhead into said permafrost zone, c. suspending a lower section of said protective casing from said surface casing at a downhole location above the location hereinafter set forth in step (e), d. locating within said well and within said protective casing a production casing which extends from the wellhead through said permafrost zone to the subterranean formation, and e. suspending a lower section of said production casing from said protective casing at a downhole location within said protective casing and below the top of said permafrost zone.

Claim 17

In a method of completing a well extending from a wellhead through a permafrost zone of the earth to an underlying subterranean formation, the steps comprising: a. locating within said well a surface casing which extends downwardly from the wellhead into said permafrost zone, b. locating within said well and within said surface casing a protective casing which extends downwardly from the wellhead into said permafrost zone, c. suspending a lower section of said protective casing from said surface casing at a downhole location above the location hereinafter set forth in step (e), d. locating within said well and within said protective casing a production casing which extends from the wellhead through said permafrost zone to the subterranean formation, and e. suspending a lower section of said production casing from said protective casing at a downhole location within said protective casing and below the top of said permafrost zone.