Offshore drilling structure

Claim 2

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, and having ballast compartments which permit it to be raised and lowered within the water, when at a drilling site, a working platform supported above the hull, said platform and hull having openings therethrough to pass drilling equipment between the platform and the subsurface, the bottom of the hull having a recessed area about the opening in the hull, said hull having holes connecting said recessed area with its top, and a thruster mounted within each hole for reducing the pressure within the recessed area so that, when the hull is supported on the subsurface, soil from the subsurface may be drawn into the recessed area.

Claim 3

An offshore drilling structure of the character defined in claim 1, including heating and cooling means in the hull adjacent said recessed area.

Claim 4

An offshore drilling structure of the character defined in claim 1, including means for supplying compressed air to said recessed area in order to force water therefrom and thereby reduce the draft of the hull.

Claim 5

An offshore drilling structure of the character defined in claim 3, wherein said air supplying means includes a source of compressed air, and means connecting the source with the holes in the hull.

Claim 6

An offshore drilling structure of the character defined in claim 1, wherein the outer sides of the hull include upper downwardly and outwardly extending portions, and lower downwardly and inwardly extending portions which intersect beneath the normal draft level.

Claim 7

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, a working platform upon which drilling equipment may be supported, legs supporting the platform above the hull, said hull and legs having ballast compartments which permit the hull to be raised and lowered within the water, when at a drilling site, said platform and hull having openings therethrough to pass drilling equipment between the platform and the subsurface, the bottom of the hull having a recessed area about the opening in the hull, said hull having holes connecting said recessed area with its top, and a thruster mounted within each hole for reducing the pressure within the recessed area so that, when the hull is supported on the subsurface, soil from the subsurface may be drawn into the recessed area.

Claim 8

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, a working platform upon which drilling equipment may be supported, legs supporting the platform above the hull, said hull and legs having ballast compartments which permit the hull to be raised and lowered within the water, when at a drilling site, said platform and hull having openings therethrough to pass drilling equipment between the platform and the subsurface, the bottom of the hull having a recessed area about the opening in the hull, said hull having holes connecting said recessed area with its top, and a thruster mounted within each hole for reducing the pressure within the recessed area so that, when the hull is supported on the subsurface, soil from the subsurface may be drawn into the recessed area.

Claim 9

An offshore drilling structure of the character defined in claim 6, including heating and cooling means in the hull adjacent said recessed area.

Claim 10

An offshore drilling structure of the character defined in claim 6, including means for supplying compressed air to said recessed area in order to force water therefrom and thereby reduce the draft of the hull.

Claim 11

An offshore drilling structure of the character defined in claim 8, wherein said air supplying means includes a source of compressed air, and means connecting the source with the holes in the hull.

Claim 12

An offshore drilling structure of the character defined in claim 6, wherein the outer sides of the hull include upper downwardly and outwardly extending portions, and lower downwardly and inwardly extending portions which intersect beneath the normal draft level.

Claim 13

An offshore drilling structure of the character defined in claim 10, wherein each of the legs extends upwardly and inwardly from the upper portions of the outer sides of the hull.

Claim 14

An offshore drilling structure of the character defined in claim 6, wherein the outer sides of the hull have upwardly and inwardly extending portions, and each of the legs extends upwardly and inwardly from the hull as substantial continuations of said portions of the platform.

Claim 15

An offshore drilling structure of the character defined in claim 12, including a downwardly and outwardly tapered shroud about each leg.

Claim 16

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, a working platform upon which drilling equipment may be supported, legs supporting the hull above the hull, said hull and legs having ballast compartments which permit the hull to be raised and lowered within the water, when at a drilling site, said platform and hull having openings therethrough to pass drilling equipment between the hull and the subsurface, said hull having holes therein connecting the top and bottom therein and arranged substantially symmetrically about the opening in the hull, a thruster mounted with each hole with its axis of rotation arranged substantially coaxially thereof, and means for selectively reversing the axial direction in which thrust from each of the thrusters is effective.

Claim 17

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, a working platform upon which drilling equipment may be supported, legs supporting the hull above the hull, said hull and legs having ballast compartments which permit the hull to be raised and lowered within the water, when at a drilling site, said platform and hull having openings therethrough to pass drilling equipment between the hull and the subsurface, said hull having holes therein connecting the top and bottom therein and arranged substantially symmetrically about the opening in the hull, a thruster mounted with each hole with its axis of rotation arranged substantially coaxially thereof, and means for selectively reversing the axial direction in which thrust from each of the thrusters is effective.

Claim 18

An offshore drilling structure of the character defined in claim 14, wherein the bottom of the hull has a recessed area about the opening in the hull, and the lower end of each of said holes connects with the recessed area.

Claim 19

An offshore drilling structure of the character defined in claim 15, wherein the recessed area comprises a plurality of recesses arranged about opening in the hull, and the lower end of at least one hole connects with each recess.

Claim 20

An offshore drilling structure of the character defined in claim 16, including heating and cooling means in the hull adjacent each recess.

Claim 21

An offshore drilling structure of the character defined in claim 16, including means for supplying compressed air to each recess in order to force water therefrom and thereby reduce the draft of the hull.

Claim 22

An offshore drilling structure of the character defined in claim 18, wherein said air supplying means includes a source of compressed air, and means connecting the source with the holes in the hull.

Claim 23

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, and having ballast compartments which permit it to be raised and lowered within the water, when at a drilling site, a working platform supported above the hull, said platform and hull having openings therethrough to pass drilling equipment between the platform and the subsurface, the bottom of the hull having a recessed area about the opening in the hull, said hull having first and second sets of holes connecting said recessed area with its top, a thruster mounted within each hole of the first set for reducing the pressure within the recessed area so that, when the hull is supported on the subsurface, soil from the subsurface may be drawn into the recessed area, and a variable orifice arranged in each hole of the second set so as to supply said thrusters with a continuing supply of water.

Claim 24

An offshore drilling structure, comprising a hull adapted to float on the water surface, during transit, and having ballast compartments which permit it to be raised and lowered within the water, when at a drilling site, a working platform supported above the hull, said platform and hull having openings therethrough to pass drilling equipment between the platform and the subsurface, the bottom of the hull having a recessed area about the opening in the hull, said hull having first and second sets of holes connecting said recessed area with its top, a thruster mounted within each hole of the first set for reducing the pressure within the recessed area so that, when the hull is supported on the subsurface, soil from the subsurface may be drawn into the recessed area, and a variable orifice arranged in each hole of the second set so as to supply said thrusters with a continuing supply of water.

Claim 25

An offshore drilling structure of the character defined in claim 20, including heating and cooling means in the hull adjacent said recessed area.

Claim 26

An offshore drilling structure of the character defined in claim 20, including means for supplying compressed air to said recessed area in order to force water therefrom and thereby reduce the draft of the hull.

Claim 27

An offshore drilling structure of the character defined in claim 22, wherein said air supplying means includes a source of compressed air, and means connecting the source with the first set of holes in the hull.

Claim 28

An offshore drilling structure of the character defined in claim 20, wherein the outer sides of the hull include upper downwardly and outwardly extending portions, and lower downwardly and inwardly extending portions which intersect beneath the normal draft level.

Claim 29

An offshore drilling structure of the character defined in claim 20, including means for selectively reversing the axial direction in which thrust from each of the thrusters is effective.

Claim 30

An offshore drilling structure of the character defined in claim 22, including means for selectively reversing the axial direction in which thrust from each of the thrusters is effective.