Marine-drilling sub-base assembly for a soft-bottom foundation

Claim 2

A drilling sub-base assembly for use at a site under a body of water having a soft-bottom foundation wherein drilling operations are conducted through a moon pool of an offshore drilling vessel, comprising: a main section of the drilling sub-base assembly dimensioned for ease of passage through the moon pool, said main section having an aperture formed therein and being adapted to be positioned on the underwater bottom; and secondary sections pivotally affixed to said main section on at least two opposite sides thereof to hang from said main section to be in a substantially vertical position with respect thereto when the drilling sub-base assembly is located in the moon pool so that the drilling sub-base assembly may pass therethrough and said secondary sections in a substantially horizontal position relative to said main section when said drilling sub-base assembly is positioned on the underwater bottom wherein said secondary sections are restrained from moving to a position above the horizontal with respect to said main section so that the necessary foundational base for the carrying-on of drilling operations is provided.

Claim 3

A drilling sub-base assembly for use at a site under a body of water having a soft-bottom foundation wherein drilling operations are conducted through a moon pool of an offshore drilling vessel, comprising: a main section of the drilling sub-base assembly dimensioned for ease of passage through the moon pool, said main section having an aperture formed therein and being adapted to be positioned on the underwater bottom; secondary sections pivotally affixed to said main section on at least two opposite sides thereof to hang from said main section to be in a substantially vertical position with respect thereto when the drilling sub-base assembly is located in the moon pool so that the drilling sub-base assembly may pass therethrough and said secondary sections in a substantially horizontal position relative to said main section when said drilling sub-base assembly is positioned on the underwater bottom in order to provide the necessary foundational base for the carrying-on of drilling operations; positioning means on the drilling sub-base assembly for providing that said secondary sections are in their substantially horizontal position when the drilling sub-base assembly is positioned on the underwater bottom and in their substantially vertical position when the drilling sub-base assembly is in the moon pool; and restraint means on the drilling sub-base assembly for preventing said secondary sections from moving to a position above the horizontal with respect to said main section when the drilling sub-base assembly is positioned on the underwater bottom so that the necessary foundational base for carrying-on drilling is established.

Claim 4

A drilling sub-base assembly for use at a site under a body of water having a soft-bottom foundation wherein drilling operations are conducted through a moon pool of an offshore drilling vessel, comprising: a main section of the drilling sub-base assembly dimensioned for ease of passage through the moon pool, said main section having an aperture formed therein and being adapted to be positioned on the underwater bottom; secondary sections pivotally affixed to said main section on at least two opposite sides thereof to hang from said main section to be in a substantially vertical position with respect thereto when the drilling sub-base assembly is located in the moon pool so that the drilling sub-base assembly may pass therethrough and said secondary sections in a substantially horizontal position relative to said main section when said drilling sub-base assembly is positioned on the underwater bottom in order to provide the necessary foundational base for the carrying-on of drilling operations; positioning means on the drilling sub-base assembly for providing that said secondary sections are in their substantially horizontal position when the drilling sub-base assembly is positioned on the underwater bottom and in their substantially vertical position when the drilling sub-base assembly is in the moon pool; and restraint means on the drilling sub-base assembly for preventing said secondary sections from moving to a position above the horizontal with respect to said main section when the drilling sub-base assembly is positioned on the underwater bottom so that the necessary foundational base for carrying-on drilling is established.

Claim 5

The drilling sub-base assembly of claim 2 wherein said secondary sections are pivotally affixed to each side of said main section.

Claim 6

The drilling sub-base assembly of claims 2 or 3 wherein said positioning means comprises: tag line means affixed to said secondary sections to extend to the surface of the body of water in which said drilling sub-base assembly is located for raising said secondary sections from their substantially vertical position into their substantially horizontal position after the drilling sub-base has cleared the moon pool so that the drilling sub-base assembly may be set into position on the underwater bottom.

Claim 7

The drilling sub-base assembly of claim 4 wherein said positioning means further comprises locking means for securing said secondary sections in their horizontal position.

Claim 8

The drilling sub-base assembly of claims 2 or 3 wherein said positioning means comprises: buoyancy means affixed to said secondary sections for applying a sufficient buoyant force to said secondary sections so that said secondary sections are in their substantially horizontal position when the drilling sub-base assembly is set into position on the underwater bottom wherein said secondary sections are in their substantially vertical position when said drilling sub-base assembly is in the moon pool.

Claim 9

The drilling sub-base assembly of claim 6 wherein said buoyancy means comprises flotation can means affixed to said secondary sections and control means for controlling the operation of said flotation can means.

Claim 10

The drilling sub-base assembly of claim 6 wherein said buoyancy means comprises buoyancy pods affixed to said secondary sections.

Claim 11

The drilling sub-base assembly of claim 8 wherein said buoyancy means further comprises latching means for holding said secondary sections in their substantially vertical position when the drilling sub-base assembly is located in the moon pool and means for operating said latching means so that said secondary sections are free to move to their substantially horizontal position once the drilling sub-base assembly has cleared the moon pool so that the drilling sub-base assembly may be set into position on the underwater bottom.

Claim 12

Apparatus for use at a subsea drilling site wherein drilling operations are conducted through a moon pool of limited size of an offshore floating structure, comprising: a drilling sub-base assembly that is to be located at a subsea location where unstable soil conditions exist such that the underwater bottom provides relatively weak foundational footing for the carrying-on of drilling operations, said drilling sub-base assembly including a main section dimensioned to freely travel through the main pool of the offshore structure and having a central aperture extending therethrough, secondary sections pivotally affixed on at least two opposite sides of said main section to hang in a substantially vertical relationship relative to said main section when said drilling sub-base assembly is located in the moon pool of the offshore structure so that said drilling sub-base assembly may travel through the moon pool of the offshore structure and said secondary sections adapted to extend from said main section to be in a substantially horizontal relationship therewith when said drilling sub-base assembly is set into position on the underwater bottom to provide the foundational base necessary for the carrying-on of drilling operations, and means on said drilling sub-base assembly for providing that said secondary sections hang from said main section in substantially vertical relationship therewith when said drilling sub-base assembly is located in the moon pool of the offshore structure and for providing that said secondary sections extend from said main section and are restrained in a horizontal relationship therewith when said drilling sub-base assembly is positioned on the underwater bottom so that the necessary foundational base for drilling is established.

Claim 13

Apparatus for use at a subsea drilling site wherein drilling operations are conducted through a moon pool of limited size of an offshore floating structure, comprising: a drilling sub-base assembly that is to be located at a subsea location where unstable soil conditions exist such that the underwater bottom provides relatively weak foundational footing for the carrying-on of drilling operations, said drilling sub-base assembly including a main section dimensioned to freely travel through the main pool of the offshore structure and having a central aperture extending therethrough, secondary sections pivotally affixed on at least two opposite sides of said main section to hang in a substantially vertical relationship relative to said main section when said drilling sub-base assembly is located in the moon pool of the offshore structure so that said drilling sub-base assembly may travel through the moon pool of the offshore structure and said secondary sections adapted to extend from said main section to be in a substantially horizontal relationship therewith when said drilling sub-base assembly is set into position on the underwater bottom to provide the foundational base necessary for the carrying-on of drilling operations, and means on said drilling sub-base assembly for providing that said secondary sections hang from said main section in substantially vertical relationship therewith when said drilling sub-base assembly is located in the moon pool of the offshore structure and for providing that said secondary sections extend from said main section and are restrained in a horizontal relationship therewith when said drilling sub-base assembly is positioned on the underwater bottom so that the necessary foundational base for drilling is established.

Claim 16

The method of claim 11 wherein said drilling sub-base assembly is to be removed from the bottom, comprising: raising said drilling sub-base assembly from the underwater bottom; and moving said secondary sections from said substantially horizontal position into said substantially vertical position prior to raising said drilling sub-base assembly through the moon pool.