FR2548367A1 - APPARATUS AND METHOD FOR DETECTING LEAKAGE IN A TENDERED PLATFORM PLATFORM TENSIONER - Google Patents

Abstract

The invention relates to a device and a method for detecting leaks in tubular rods filled with liquid under pressure. EACH TENSION 6 CONTAINS A LIQUID OF LOWER DENSITY THAN SEA WATER IN ORDER TO IMPROVE BUOYANCY AND REDUCE THE WEIGHT SUPPORTED BY A FLOATING STRUCTURE 2, 3. A CORROSION INHIBITOR LIQUID MIXED WITH THE LIQUID CONTAINED IN THE TENSION ROD , REDUCES CORROSION OF THE INTERNAL WALL OF THIS TIE ROD. FIELD OF APPLICATION: FLOATING PLATFORMS FOR DRILLING AND OPERATING OIL AND GAS WELLS, ETC.

Description

The invention relates generally

  Tie rods or tensioners of tensioned rope platforms.

  The invention more particularly relates to tie rods or tensioners filled with pressurized liquid, and relates to the detection of leaks, buoyancy and corrosion resistance. A change in pressure indicates a deficiency of the structure. the buoyancy of the tie rods or tensioners reduces the weight supported by the floating structure. Corrosion resistance extends the service life

useful pulling.

  In deep water, the use of bottom-based foundations for drilling and oil well operations is prohibitively expensive because of the expense of manufacturing and installing such wells. large structures In deeper waters exceeding 300 m, floating marine structures moored at the bottom of the sea may be used to carry out drilling and production operations.

in a cost-effective way.

  When the water depth exceeds 300 m, the tethered cable platform concept can be used for drilling and oil production operations. A tethered cable platform comprises a floating marine structure moored to fixed points of anchoring to the seabed by means of vertically tensioned cables, also called turnbuckles or drawbars Drilling, production and processing equipment, as well as crew quarters, are placed in or on the floating structure. Tensioners or tie rods can be of two designs, namely cables and tubular legs. U.S. Patent No. 4,285,615 discloses a docking apparatus for a structure floating on a body of water, comprising a corrosion resistant cable system, which comprises a multi-drains cable having voids between adjacent strands "; U.S. Patent No. 4,226,555 discloses a mooring system for a stretched cable platform comprising a tensioned cable which has a plurality of tubular members interconnected by screw connections "L". use of previously tensioned vertical mooring elements prevents vertical movements, but allows lateral movement of the floating structure

  When the waves pass The application of a pre-tension is carried out by deballasting the floating marine structure after the tie rods have been mounted between this structure and anchoring bases fixed to the bottom of the sea.

  An inspection of the tie rods or turnbuckles is necessary, which is both a maintenance expense and a safety precaution. The repair and replacement of the tie rods are both very expensive and difficult operations. The cracks and corrosion due to Seawater exposure decreases the tensile strength and service life of the tie rod The desirability of reducing tie rod corrosion has been recognized in the art. The aforementioned patent N 4,285,615 describes a device designed to provide corrosion resistance to a tensioned cable, this device isolating the steel cable.

  of the surrounding environment consisting of seawater.

  The invention relates to a method and a device for the detection of structural defects affecting a tubular tie rod, for increasing buoyancy.

  of this tie rod and to extend its useful life.

  The invention relates to a method and a device for detecting leaks in a tubular tie rod or tensioner, for increasing its buoyancy and for extending its useful life. Several segments of the tie rod, each comprising a tubular element and closable couplings, are assembled to form

  This tubular tie is filled with a corrosion-preventing liquid, having a density less than that of seawater. A compressor is used to pressurize the contents of the tubular tie rod and manometers detect variations. pressure.

  The corrosion preventing liquid protects the inner wall of the tie rod against corrosion by seawater. The liquid having a density lower than that of seawater increases the buoyancy of each tie rod, thereby reducing the weight supported by the structure. floating marine Pressure variations indicate cracks or perforations

  the tie rod, or a faulty coupling joint.

  The invention relates to a method and apparatus for detecting leaks in a tubular tie, to increase the buoyancy of this tie rod and to extend its useful life. A method and apparatus for detecting leaks indicative of defects The increased buoyancy of the tie rod reduces the weight supported by the floating marine structure and allows a more efficient design of this structure. Increasing the service life of the tie rod improves the safety and reduces routine maintenance costs. the performance of deep-water drilling by reducing maintenance,

  repair and replacement of the tie rods.

  The subject of the invention is also a

  An improved design tensioned platform using the present invention as described above.

  The invention will be described in more detail with reference to the accompanying drawing as a non-limiting example and in which: Figure 1 is a schematic elevation, partly in section, of a platform with tensioned cables; Figure 2 is a partial enlarged elevation on an enlarged scale of one of the tie rods shown in Figure 1; and FIG. 3 is a section of the tie rod along the line 3-3 of FIG. 2. FIG. 1 is a diagrammatic elevation

  partially cut, a platform 1 with tensioned cables installed on a drilling site There is provided a lower platform 2 on which can be mounted the living quarters of the crew, the equipment of well testing and treatment equipment.

  There is also provided an upper platform 3 on which can be mounted a pilot's cabin, cranes, the drill tower, a ripable base, the drill string and a helicopter landing area.

  Similar conveniences can also be placed on the upper and lower platforms, as is well known to the oil exploration and production specialist. Platforms 2 and 3 are supported by a plurality of annular columns. platform & tensioned cables is in its floatation state as shown, columns 4 and pontoons 5 extend below the surface of the water Several tie rods 6 extend between each support column 4 and anchoring means comprising a foundation plate 7 fixed to the bottom 8 of the sea by means of friction piles 9, so as to reduce the movement of the structure A drill string 10 and extension tubes 11 extend 30 of the platform 1 or 2 to the bottom 8 of the sea, passing between the pontoons 5, during the drilling and production operations A base plate 12 holds the extension tubes in a fixed position by

compared to the bottom 8 of the sea.

  FIG. 2 is a detailed view on an enlarged scale of a tie rod or tensioner 6 represented in the form of a tubular element. Several pulling segments, each consisting of a tubular element and of couplings that can be closed, are assembled to form The tubular element generally comprises a relatively thin wall with respect to its overall diameter. A tubular element having inside and outside diameters of 45 and 50 cm respectively has been designed. FIG. 3 represents a section of the tie rod of the figure 2, next

line 3-3.

  According to the present invention, a liquid, advantageously a liquid preventing corrosion

  and having a density lower than that of seawater, enters the tie rod through a conduit at its upper end A liquid mixture of soft water and hydrazine meets the above criteria.

  After the introduction of the liquid into the tie rod, a compressor 13 applies a pressure, via the conduit, to the contents of the tie rod. A pressure greater than the maximum hydrostatic pressure exerted by the seawater on the tie rod is recommended for avoid the case where the pressure inside the tie rod is equal to the pressure of the seawater at the same height A positive net internal pressure is used to detect a leakage A valve is closed in order to retain the contents under pressure Pressure gauges monitor the pressure in the draft Pressure reductions, above a predetermined value, produce a signal informing

  the crew members of a defective tie rod.

  Corrosion-Resistant Liquid Protects the Inner Walls of the Tubular Tie from Exposure to Seawater A liquid with a density lower than that of seawater provides buoyancy and reduces the weight of the tie rod supported by the structure Floating except for any deficiency at pressurization, a pressure variation indicates a leak affecting the tie rod and may be attributed to a crack or perforation of the wall of the tie rod, or to a

defective coupling seal.

  It goes without saying that many modifications can be made to the device and the method described and shown without departing from the scope of the invention.

Claims (14)

  Apparatus for detecting a leak in a stretched cable platform tie, characterized in that it comprises a fluid tight tubular tie rod (6), means for supplying the tie rod with fluid, means (13) intended to pressurize the liquid, means for controlling the pressure, said control means detecting variations in the pressure of the liquid in the tie rod, means for connecting an upper end of the tie rod to a floating marine structure (2 , 3), and means for connecting a lower end of the tie rod to anchoring means (7, 9) attached to the bottom of the sea.   2 Apparatus for detecting a leak in a tie rod of a platform with tensioned cables, characterized in that it comprises a floating marine structure (2, 3), anchoring means (7, 9) fixed to the bottom of the sea, at least one tie rod (6) mounted between the floating marine structure and the anchoring means and consisting of a fluid-tight tubular element, means for supplying the tie rod with fluid, means (13) for pressurizing the liquid, and means for controlling the pressure, said control means detecting changes in the pressure liquid in the tie rod.   3 Apparatus according to one of the claims   1 and 2, characterized in that the liquid is water.   Apparatus according to one of claims 1 and 2, characterized in that the liquid is a hydrocarbon.   Apparatus according to one of the claims   1 and 2, characterized in that the liquid comprises,   in a mixture, a corrosion inhibitor.   Apparatus according to one of the claims   1 and 2, characterized in that the density of the liquid   is less than that of seawater.   Apparatus according to one of the claims   1 and 2, characterized in that the pressure of the liquid in the tie rod is greater than the maximum hydrostatic pressure exerted by the seawater on the tie rod. 8 Method for detecting a leak in a tie rod of a platform with tensioned cables, characterized in that it consists in mounting a tie between a marine floating structure and anchoring means fixed to the bottom of the sea, the pulling being a fluid-tight tubular member, supplying the tie rod with fluid, pressurizing the fluid, and controlling the pressure of the liquid in the tie rod to detect leaks in the latter.   Process according to claim 8, characterized in that the liquid is water.   Process according to claim 8, characterized in that the liquid is a hydrocarbon.   11. Process according to claim 8, characterized in that the liquid comprises, as a mixture, a corrosion inhibitor.   Process according to Claim 8, characterized in that the density of the liquid is lower to that of seawater.   Method according to claim 8, characterized in that the liquid maintains a pressure greater than the maximum hydrostatic pressure exerted by the sea water on the pulling.