Patent EA-000448-B1 (EA)
Title: Off-shore production platform
Inventor: TOMA PIER-ARMAN
IPC: B63B35/44
Filed: 1997-01-24
Abstract: 1. Off-shore production platform, especially off-shore oil production platform, of the type including an upper barge (1) stretching above the level of the sea and connected to a completely submerged hollow lower base (3) by partially submerged connecting legs (2) forming a buoyancy tank and stretching substantially vertically, characterized in that the legs (2) along their submerged height include at least two successive portions (10, 14), a first portion (10) with solid walls delimiting a closed space and forming a buoyancy tank and a second portion (14) with openwork sidewall, the interior space of this second portion (14) being open to the surrounding marine environment. 2. Platform according to Claim 1, characterized in that the second portion (14) with openwork sidewall is a metal lattice structure (18). 3. Platform according to Claim 1 or 2, characterized in that the second portion (14) with openwork sidewall is arranged between the first portion (10) with solid walls and the base (3). 4. Platform according to any one of the preceding Claims characterized in that the first portion (10) with solid walls stretches at least partially immediately below said barge (1). 5. Platform according to any one of the preceding Claims, characterized in that the first portion (10) and second portion (14) are dimensioned such that over the usual swell period range, the pressure force (Fp) exerted on the first portion (10) with solid walls substantially compensates for the acceleration force (Fa) of the platform. 6. Platform according to Claim 5, characterized in that the first portion and second portion are dimensioned such that for two values of swell period lying within the usual swell period range, the pressure force (Fp) and the acceleration force (Fa) are equal. 7. Platform according to Claim 6, characterized in that the smallest value of swell period for which the pressure force (Fp) and. the acceleration force (Fa) equal, is greater than 4 seconds. 8. Platform according to any one of the preceding Claims, characterized in that the submerged height of the second portion (14) lies between one quarter and three quarters of the total submerged height of the leg (2). 9. Platform according to Claim 8, characterized In that the submerged height of the second portion (14) lays between substantially 0.4 and substantially 0.65 times the total submerged height of the leg (2). 10. Platform according to any one of the preceding Claims, characterized in that the legs (2) have a cylindrical external overall shape. 11. Platform according to any one of the preceding Claims, characterized in that the base (3) includes at least one passage (20) passing substantially vertically right through it. 12. Platform according to any one of the preceding Claims, characterized in that the base (3) is filled with a fluid forming ballast/ particularly with seawater. 13. Platform according to any one of the preceding Claims, characterized in that the barge (1) is mounted so that it can be moved along the legs (2) and in that mechanisms (6) are provided for the relative movement and locking of the barge (1) with respect to the legs (2). 14. Platform according to any one of the preceding Claims, characterized in that the said second portion (14) with openwork sidewall is arranged between two portions with solid walls along the submerged height of the legs (2).