US3646770A - Method and apparatus for stabilizing an offshore drilling platform structure - Google Patents

Method and apparatus for stabilizing an offshore drilling platform structure Download PDF

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Publication number
US3646770A
US3646770A US43875A US3646770DA US3646770A US 3646770 A US3646770 A US 3646770A US 43875 A US43875 A US 43875A US 3646770D A US3646770D A US 3646770DA US 3646770 A US3646770 A US 3646770A
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United States
Prior art keywords
pile
water
floor
fluid
pump
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Expired - Lifetime
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US43875A
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English (en)
Inventor
Francois Van Daalen
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Shell USA Inc
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Shell Oil Co
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    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D3/00—Improving or preserving soil or rock, e.g. preserving permafrost soil
    • E02D3/02—Improving by compacting
    • E02D3/10—Improving by compacting by watering, draining, de-aerating or blasting, e.g. by installing sand or wick drains
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D27/00—Foundations as substructures
    • E02D27/32—Foundations for special purposes
    • E02D27/52—Submerged foundations, i.e. submerged in open water
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/22—Piles
    • E02D5/226—Protecting piles
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/22—Piles
    • E02D5/54—Piles with prefabricated supports or anchoring parts; Anchoring piles
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
    • E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
    • E02D5/74—Means for anchoring structural elements or bulkheads

Definitions

  • ABSTRACT A method and apparatus for stabilizing an offshore drilling platform structure adapted to rest on the floor of a body of water by perforating at least one of the piles of the structure, thereby establishing fluid communication between the soil surrounding the pile and the interior of the pile. The fluid level in the pile is then maintained at a relatively constant low level.
  • This invention relates to offshore drilling platform structures, and, more particularly, to a method and apparatus for stabilizing an offshore platform structure.
  • FIG. 1 is a vertical sectional view of preferred apparatus for carrying out the technique of my invention
  • FIG. 2 is a detailed vertical sectional view of a portion of the apparatus of FIG 1;
  • FIGS. 3 and 4 are vertical sectional views, partly schematic, of an example of the technique of my invention.
  • the axial capacity of friction piles depends on the adhesion that is developed along the surface of the pile. This adhesion is related to the shear strength of .the soil surrounding the pile. TI-Ie relation between soil/pile adhesion and soil shear strength is complicated and not fully understood. Except for very stiff clays at shallow depths, an increase in shear strength generally corresponds to increased adhesion. Therefore, if the shear strength of the surrounding soil can be increased, pile capacity can be increased without altering the dimensions of the piles.
  • FIG. 1 shows an offshore drilling structure having a plurality of legs (only legs 11 and 12 being shown in FIG. I) for supporting a platform 13 above the surface 14 of a body of water, such as ocean 15.
  • Legs 11 and 12 rest on the mudline or floor 16 of the body of water 15, the legs of structure 10 having friction pile means associated therewith extending into the soil of floor 16 for maintaining the legs in position on the floor l6 and thus stabilizing structure 10.
  • pile means 17 and 18, shown in dottedlines, are associated with legs 11 and 12, respectively.
  • Suitable bracing means 19 preferably extend between the legs of structure 10 for bracing structure 10 for bracing structure 10 as is well known in the art.
  • the piling means 18 of leg 12 includes a drainage pile 20 which is driven therethrough into the ocean floor 16.
  • Pile 20 includes at its lower end a penetrating portion 21 for penetrating the ocean floor 16.
  • Pile 20 is further perforated as at perforations 22 and 23 for reasons to be discussed further hereinbelow. Although only two such perforations are shown, obviously one or more perforations may be formed in pile 20 in accordance with the teachings of my invention, preferably at a significant distance below the floor 16.
  • the drainage pile 20 exemplifies one means for establishing fluid communication between the interior of a pile and the surrounding soil at a depth below the floor of the body of water.
  • fluid communication can be established by driving an unperforated pile and then perforating it in situ, by driving a preformed porous concrete pile, by casting such a concrete pile in place, or the like.
  • Such a pile can be substantially any axial load-bearing elongated hollow structure and substantially any means can be used to establish fluid communication between its interior and the surrounding soil.
  • a tubing string 24 preferably carries at its lower end a pump 25, or similar pumping means, for pumping fluid entering pile 20 through perforations 22 and 23.
  • a spider 26 or similar device is preferably connected to pump 25 to maintain the pump 25 in place, i.e., in spaced relation from the wall of the pile 20.
  • Suitable holes 27 are formed in pump 25 for permitting the aforementioned fluid from entering pump 25.
  • a conventional sucker rod 28 extends downwardly through leg 12 into fluid communication with pump 25 for removing fluids pumped by pump 25 to a remote location, such as platform 13 where the fluid is discharged onto water surface 14.
  • the drainage pile 20 of structure 10 is preferably applied thereto during the construction of structure 10.
  • fluid is withdrawn from the soil surrounding the pile 20 through perforations 22 and 23 formed therein until the soil is compacted to a shear strength equaling that of soil at a deeper depth.
  • the effective stress of the soil surrounding the pile 20 is increased by lowering the pore water pressure in the surrounding soil.
  • the perforated pile 20 acts as a sand drain since gravity drainage of water occurs from the soil through perforations 22 and 23.
  • the water being drained into pile 20 is kept at a constant low level by pumping it through pump 25 and sucker rod 28 to he water surface.
  • the pressure of the pore water in the soil decreases as a function of time and place and thus a consolidation process begins. This decrease in pore pressure results in an increased effective stress and thus in an increased shear strength.
  • the capacity of pump 25 and the number of perforations are preferably so arranged that substantially all of the water present in the soil that drains into pile 20 during a period of at least several weeks is removed.
  • the water-removing equipment i.e., pump 25, perforations 22 and23, sucker rod 28, etc.
  • the water-removing equipment is preferably arranged for continuous or intermittent operation throughout the period in which a high load-bearing capacity is important.
  • drain hole or holes may be formed in the piles already in place and pumping units similar to unit 25 and sucker rod 28 may be installed therein in the manner disclosed in a copending applic t qntp l lmsontSsr-figufi.
  • a drain hole is prepared by sonically driving a hollow, bore-forming tool downwardly into the earths formation, removing the core of earth material out through the center of the bore-forming tool, placing an eduction or jet-pumping unit through the bore of the tool into the bottom of the borehole, and filling the borehole with a granular material such as sand either prior to or simultaneously with withdrawal of the boreforming tool.
  • EXAMPLE Leg 12 with its associated drainage pile 20 is shown schematically in FIG. 3.
  • WI refers to the water level in pile 20.
  • a plurality of perforations are formed in pile 20, the total extent of the perforations being indicated as a permeable part L of pile 20.
  • Gravity drainage of water occurs from the soil into the pile 20 through perforated part L'.
  • the water in the pile is kept at a constant low level, i.e., W1 by pumping it to the surface (not shown in FIG. 3).
  • the pressure of the pore water in the soil decreases as a function of time and place, or, in other words, a consolidation process starts.
  • the rate at which a steady state is approached is relatively high in sand.
  • u is the neutral stress.
  • the total normal stress on a horizontal plane at that depth is:
  • h is the water depth
  • y is the water density
  • Ay is the density difference between water and air
  • Ay is the density difference between soil and water (submerged density of soil).
  • C cohesion
  • F is an improvement factor
  • K is the lateral earth pressure coefficient
  • FIG. 4 An experiment was carried out as shown in FIG. 4.
  • a pile 29 was formed comprising a 1-inch outer diameter pipe 30 perforated over a 6-inch length and covered with a screen 31.
  • the pile 2 9 was placed in a S-gallon bucket 32 after which the bucket 32 was filled with water and soil, either sand or clayi.e., tests were carried out in both sand and clay.
  • a load was transferred to the pile 29 by a string 33 connected to pipe 30 acting over two pulleys 34 and 35.
  • a weight 36 was attached to the free end of string 33.
  • the deflection at the pile head was measured by a dial gauge 37 at the pile head.
  • Table I The results of the tests are shown in Table I.
  • a method for stabilizing an offshore platform structure adapted to rest on the floor of a body of water and having a plurality of friction piles extending into the floor of said body of water comprising the steps of:
  • step of maintaining the fluid level in said pile at a relatively constant low level includes the step of intermittently pumping fluid from said soil to said body of water.
  • Apparatus for stabilizing an offshore drilling platform structure adapted to rest on the floor of a body of water comprising:
  • an offshore drilling platform structure having a plurality of legs adapted to rest on the floor of a body of water;
  • pile means extending into the floor of said body of water associated with each of said legs adapted to maintain said legs in a stable position on said floor of said body of water;
  • fluid drain means formed in at least one of said pile means below said floor of said body of water communicating with fluid present in the soil forming said floor of said body of water;
  • the fluid drain means includes a plurality of perforations extending along said pile means a substantial distance below said floor of said body of water.
  • said pumping means includes a pump in fluid communication with said fluid drain means
  • sucker rod extends through said tubing string and said tubing string extends through said pile means.
  • sucker rod extends to said water surface 8.
  • spacer means associated with said pump for spacing said pump from the wall of said pile means.

Landscapes

  • Engineering & Computer Science (AREA)
  • Structural Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Paleontology (AREA)
  • Civil Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Agronomy & Crop Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Soil Sciences (AREA)
  • Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
  • Fertilizers (AREA)
US43875A 1970-06-05 1970-06-05 Method and apparatus for stabilizing an offshore drilling platform structure Expired - Lifetime US3646770A (en)

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US4387570A 1970-06-05 1970-06-05

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US3646770A true US3646770A (en) 1972-03-07

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Country Status (6)

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US (1) US3646770A (enExample)
CA (1) CA950217A (enExample)
DE (1) DE2127615A1 (enExample)
FR (1) FR2095881A5 (enExample)
GB (1) GB1351992A (enExample)
NL (1) NL7107604A (enExample)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6036404A (en) * 1993-08-31 2000-03-14 Petroleo Brasileiro S.A.-Petrobras Foundation system for tension leg platforms
US6318933B1 (en) 1993-08-31 2001-11-20 Petroleo Brasileiro S.A. Foundation system for tension leg platforms
CN109629568A (zh) * 2018-12-30 2019-04-16 中交第三航务工程局有限公司江苏分公司 海上风电导管架基础钢管桩用浮式稳桩平台的沉桩工艺
US10309072B2 (en) * 2016-11-08 2019-06-04 Guangxi University Water-permeable pipe pile system capable of accelerating soil consolidation and method of using the same
CN110144904A (zh) * 2019-06-06 2019-08-20 招商局重庆交通科研设计院有限公司 一种具有自锚固功能的仰斜式排水结构及其施工方法
CN117773440A (zh) * 2024-02-26 2024-03-29 广州文船重工有限公司 一种风电导管架的可移动式内胆工装

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2895301A (en) * 1955-02-08 1959-07-21 California Research Corp Stabilization of submarine raft foundations
US2919552A (en) * 1953-09-02 1960-01-05 Hayward John Thomson Method of stabilizing submerged hulls on sand bottoms
US3274782A (en) * 1963-07-05 1966-09-27 Richard E Landau Dewatering clayey and silty soil
US3550384A (en) * 1969-02-07 1970-12-29 Exxon Production Research Co Lateral restraint of pile within jacket leg

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2919552A (en) * 1953-09-02 1960-01-05 Hayward John Thomson Method of stabilizing submerged hulls on sand bottoms
US2895301A (en) * 1955-02-08 1959-07-21 California Research Corp Stabilization of submarine raft foundations
US3274782A (en) * 1963-07-05 1966-09-27 Richard E Landau Dewatering clayey and silty soil
US3550384A (en) * 1969-02-07 1970-12-29 Exxon Production Research Co Lateral restraint of pile within jacket leg

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6036404A (en) * 1993-08-31 2000-03-14 Petroleo Brasileiro S.A.-Petrobras Foundation system for tension leg platforms
US6142709A (en) * 1993-08-31 2000-11-07 Petroleo Brasileiro S.A. - Petrobras Foundation system for tension leg platforms
US6312195B1 (en) 1993-08-31 2001-11-06 Petroleo Brasileiro S.A. — Petrobras Method of installing foundation for tension leg platform
US6318933B1 (en) 1993-08-31 2001-11-20 Petroleo Brasileiro S.A. Foundation system for tension leg platforms
US6568880B2 (en) 1993-08-31 2003-05-27 Petroleo Brasileiro S.A. - Petrobras Foundation system for tension leg platforms
US10309072B2 (en) * 2016-11-08 2019-06-04 Guangxi University Water-permeable pipe pile system capable of accelerating soil consolidation and method of using the same
CN109629568A (zh) * 2018-12-30 2019-04-16 中交第三航务工程局有限公司江苏分公司 海上风电导管架基础钢管桩用浮式稳桩平台的沉桩工艺
CN110144904A (zh) * 2019-06-06 2019-08-20 招商局重庆交通科研设计院有限公司 一种具有自锚固功能的仰斜式排水结构及其施工方法
CN117773440A (zh) * 2024-02-26 2024-03-29 广州文船重工有限公司 一种风电导管架的可移动式内胆工装
CN117773440B (zh) * 2024-02-26 2024-04-19 广州文船重工有限公司 一种风电导管架的可移动式内胆工装

Also Published As

Publication number Publication date
GB1351992A (en) 1974-05-15
NL7107604A (enExample) 1971-12-07
CA950217A (en) 1974-07-02
FR2095881A5 (enExample) 1972-02-11
DE2127615A1 (de) 1971-12-09

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