US3107495A - Method of erecting an offshore structure - Google Patents

Description

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United States Patent Ofifice 3,107,495 Patented Oct. 22, 1963 New Jersey Filed Apr. 29, 1959, Ser. No. 809,838 2 Claims. (Cl. 61-46) This invention pertains to improvements in off-shore oil drilling constructions and construction methods, and provides for such and related applications, drilling platforms and methods of installation embodying novel and unique features which greatly reduce the time and expense involved while affording a superior type of structure.

In the past decade, commercial exploitation of offshore drilling for oil has increased enormously. In consequence, improvements in installation methods, materials and structures for such purposes have received increasing attention.

According to one construct-ion heretofore successfully employed, the drilling platform comprises a precast rectangular concrete deck frame, mounted at each of its corners on a pair of prestressed concrete, shell piles, one a plumb or vertical pile and the other 'a batter pile. This construction has the disadvantage, however, that each pair of the vertical and batter piles must be connected by means of a concrete cap which is poured in two stages. The first portion of each cap is poured before placement of the concrete deck frame. After the concrete has set, the deck frame is lowered onto the caps, whereupon the second portion of each cap is poured to finish off the structure. This is both time consuming and expensive.

In accordance with the present invention the drilling platform comprises a prefabricated superstructure of steel consisting of a skeletal framework of substantial area and depth, trussed against vertical, horizontal and corner-tcorner deflection, and on which is mounted at spaced points about its periphery, a series of upstanding collars of roughly oval contour in plan view.

The transverse dimensions of these collars are such, as in one modification, to enter a batter pile therein, or in another modification, to enter a pair of piles comprising a pair of batter piles or alternatively, a vertical and a batter pile, and with suflicient clearance, in each modification, that concrete may be subsequently poured into the space between the collar and pile or pile pair, as the case may be.

The piles are so driven, as by means of a spotting tem plate, that after they are cut off to the required elevation above the water level, their upper ends will be positioned in alignment with the respective collars of the platform as the latter is lowered into position by means of a barge crane.

For initially securing the respective collars to the so entered pile or pile pairs, preparatory to pouring the concrete, each collar has tapped therethrough at spaced points extending vertically and peripherally thereof, a series of bolts which are adjustable by a wrench to grip the so entered pile or pile pairs on all sides, thereby temporarily to support the platform on the piles. After the bolts are thus tightened, there is no relative movement between the piles and the platform frame. The space between each collar and the pile or pile pair entered therein is then filled with concrete. The motion of the piles due to wave action will not disturb the setting of the concrete.

Each of the piles is then filled with a solid plug of concrete which extends from the cut-off elevation to a point several feet below the water surface. The top of each pile or pile pair is furnished with a steel pedestal anchored in the concrete plug, to receive the drilling floor.

Thus the invention provides, in one of its aspects, a

simple means of connecting the superstructure to the piles.

Having thus described the invention in general terms, reference will now be had, for a more detailed description, to the accompanying drawings, wherein:

FIG. 1 is a view in elevation, and partly in section, of a platform superstructure and pile assembly, in accordance with the invention; while FIG. 2 is a plan view thereof, and FIG. 3 a sectional elevation at 3-3 of FIG. 2. FIG. 4 is an enlarged plan view of one of the collar and pile assemblies of the FIGS. 1-3, inclusive, showing; while FIG. 5 is a vertical section taken at 5-5 of FIG. 4. FIGS. 6 and 7 are, respectively, a plan view and a view in elevation of a collar and pile assembly, employing a pile pair consisting of a vertical pile and a batter pile assembled in the collar and secured thereto as above described. FIG. 8 is a plan view similar to FIG. 6 of another modification wherein a pair of batter piles are assembled in a collar of the superstructure.

FIGS. 9 and 10 are, respectively, views in elevation and plan, of a pile anchoring and template arrangement for adjust-ably anchoring the center or well conductor pile head at the exact location desired, and for driving the platform supporting piles thereabout in alignment with the platform collars respectively, for entry therein. FIG. 11 is an enlarged view in elevation of the upper portion of FIG. 9. FIG. 12 is a fragmentary detail of a winch arrangement for appropriately tensioning the cables of the FIGS. 9-11, inclusive, anchoring assembly.

Referring to FIGS. 1-5 inclusive, the drilling foundation therein shown, comprises a steel frame superstructure 10, mounted on four prestressed concrete, tubular or shell type piles 11-14 inclusive, of cylindrical contour disposed about a central or well conductor pile 14a. The piles are made up of centrifugally spun, precast concrete sections, each of about 16 feet in length. A plurality of longitudinally extending holes are cored at equi-spaced intervals about the circumference of the shells as they are spun, and the shell sections are fastened together by post tensioned cables extending through the core holes, as at 15, 16, FIG. 5. The pile sections may be produced "as set forth in Us. Patents 2,550,858, I. T. Parret, and 2,602,979, M. Van Buren, and joined with post tensioned cables as described in US. Patent 2,609,586, R. M. Parry.

The piles as thus assembled are of such length that when driven into the bed 17 of a body of water 18, where drilling is to be carried out, the upper ends will extend sufficiently above the water level 19, that they may be cut off to the required elevation, for mounting the superstructure 10 thereon. The steel superstructure 10 is completely prefabricated in the land-based yard as a unitary structure, which is lifted onto a barge and transported to the drill site where it is placed on the piling as described more in detail below.

As shown in FIGS. l-3 inclusive, the superstructure is of substantially rectangular configuration in elevation and in plan, having disposed at its respective corners, the above mentioned collars 20-23, inclusive, into which the piles 11-14 are respectively entered and secured to the superstructure as hereinafter explained. Extending horizontally between adjacent collars, such 'as 20, 23, are pairs of upper and lower channel members, as at 24, 25 and 26, 27, the inner faces of which are welded to the opposite ends, respectively, of vertically extending I beams, 'as at 28, 29, disposed intermediate the ends of said channel members, and to end plates disposed at the opposite ends thereof, as at 30, 31. The vertical members function as struts, and the channels and struts are braced against lateral and corner-to-corner deflection, by

3 additional I beams extending in oppositely inclined diagonal directions between the upper and lower channel pairs and adjacent verticals, as at 32, 33 and 34, 35.

A series of parallel and equi-spaced I beams, as at 41, extend between the oppositely disposed upper channel members 25 and 47, being welded at their opposite ends thereto, respectively. These beams serve as flooring beams for a steel floor grating 43 mounted thereon and secured thereto. The floor beams are in turn buttressed at intermediate points by a pair of cross or I beams 54 51, which extend beneath the floor beams, between the oppositely disposed pairs of vertical beams 52, 53 and 54, 55, respectively, being welded to these verticals.

The superstructure as thus far described is additionally braced by a series of I beams, extending diagonally beneath the floor beams, as at 56, 57, from the vertical member 58, to the vertical members 52, 53, respectively, and as at 59, 60, from the vertical members 52, 53, respectively, to the midpoint of the I beam 51. In similar fashion additional I beams extend diagonally from the midpoint of beam 50, as at 61, 62, to the vertical members 54, 55, respectively, and as at 63, 64, from these members, respectively, to the vertical member 65.

Diagonal bracing for the lower part of the superstructure, is provided by pipe sections, as at 7 -73 inclusive, which extend, respectively, etween the midpoints of adjacent lower channel members, being welded to thereat, as more particularly shown in FIG. 3, for pipe sections 70, 71, terminating at the inner lower channel members 27 and 74, respectively.

The trussing of the superstructure is thus such that the entire structure acts as a portal frame when subjected to design loads.

The well conductor pile 14a extends through the framework of the superstructure in the manner shown in FIGS. 1 and 2, and is accessible through an opening 3%} in the floor grating 48. It is braced at its upper end, by means of a clamping ring 81, from which tie rods, as at 82, 83, equipped with turnbuckles, as at 84, extend to the I beams 50, 51, being appropriately secured to each. The flooring area around the well conductor pipe is strengthened by additional flooring I beams as at 85, 86, extending between beams 50, 51, and cross beams 86a, 87, extending between beams 85, 36.

The superstructure includes a landing platform 30 carried by the lower portion of the framework and equipped with a boat fender system 91 of timbers, and also a barge fender system 92, also mounting fending timbers 93. A stairway 94 extends from the upper grating 48 to the lower grating 95 of the landing platforms. The construction of these items being conventional, requires no detailed description.

FIGS. 4 and 5 are illustrative of the corner mounting of the FIGS. l-3, inclusive, superstructure on each of the piles 11-14 inclusive. It will be observed from these views that the collar A which is typical of any of the collars 20-23 inclusive, of FIG. 1, is substantially in the form of an oval-shaped tube, i.e., oval in plan view as in FIG. 4, with the wall portion parallel to the axis of the tube, as in FIG. 5. The collar has formed integral with or welded to its outer surface at equi-spaced intervals, strengthening ribs or flanges, as at 100.

As further shown in these views, the sectional dimensions of the collar A, are substantially greater than that of the pile B entered therein, and such as to provide ample space between the two on all sides for plugging with concrete, as at 101. For example, for accommodating a pile of 54" in diameter, appropriate dimensions for the collar would be 6'9 for the longer axis, 5'6" for the shorter axis, and the height 7'2.

Tapped through the collar at vertically and circumferentially spaced intervals, are a series of threaded bolts, as at 102-105, inclusive, provided with nut heads, as at 106, for adjusting with a manually or power actuated wrench, and lock nuts, as at 107, for locking the bolts in any desired position of adjustment.

Reverting to FIGS. 1-3, as was above explained, when the piles 1 1-1 4 inclusive, have been driven to the desired depth and cut oil to the desired elevation above the water level, the superstructure 10 is lowered into position, with the collars 20-23 inclusive, aligned with the tops of the piles 1.1-1.4 inclusive, respectively, and the piles entered therein. At this stage the bolts 102-105, inclusive, FIGS. 4 and 5 are adjusted substantially to their outermost positions to provide ample clearance for entry of the pile heads into their respective collars to the extent shown in FIG. 5. The bolts are then adjusted inwardly until they grip the pile head on all sides in the manner illustrated in this figure, thus temporarily to support the superstructure 14) in the pile heads in the relative positions shown in FIG. 1. The space between each collar and pile is then filled with liquid concrete, as at 101, FIG. 5, for which purpose a temporary retaining ring is placed around the pile to close 011 the opening between the pile and the base of the collar, as at 108, FIG. 5, which may be done either before or after the pile has been entered into the collar. During the setting of the concrete, the bolts 102- 105, inclusive, grip the pile head with sutficient firmness that the motion of the piles due to wave action will not disturb the setting.

Each pile is also filled with a solid plug of liquid concrete which extends from the out 01f elevation to a point several =feet below the water level, as at 109, FIGS. 1 and 5. To retain the concrete plug during pouring and setting, a disc of wood or the like is initially thrust into the pile cavity to the desired depth and held by friction, as at 110, FIG. 1.

While the concrete of the plug is still liqu-id, the tubular base 111, FIG. 5, of a steel pedestal 112, is thrust into it to support on each pile head, a drilling fioor, as at 113, FIG. 1, for drilling floor 114.

Referring to FIGS. 9-12, inclusive, there is shown a suitable type of template and anchor line assembly for accurately spotting and driving the batter piles 11-13, inclusive, in relation to the well conductor pile 14a. The template shown generally at 115, comprises a central sleeve member 116 integral with a cap member 116a terminating in a lifting eye 116b, which assembly is sleeved over the upper end of the well pile 14a and retained by the cap 116a in the position shown in FIG. 11. To the sleeve member 116, there is pivotally attached, as at 117, a series of four radially extending arms, as at 1 18, terminating at their outer extremities in arcuately shaped guide members 119, adapted to engage and guide the batter piles 11-13, inclusive, during driving in the manner shown in FIG. 11.

During driving the arms 118 are maintained in the elevated position shown, by cables 112i), equipped with tumbuckles 121, which extend between the guide members 119 and an upper portion of the sleeve 116, as at 121. When the driving is complete, the cables 120 are released, so that the arms can be folded down in the direction of the arrows X, and thus clear the batter piles in order to permit removal of the template by the crane cable 1 16c attached to the lifting eye.

In order to pull the top of the center pile 14a, to exact location at the water level, if necessary, preparatory to driving the batter piles 11-13, inclusive, anchor lines, as at 125, may be utilized, which extend from small hand or power driven winches, as at 126, mounted on the sleeve member 116, thence to anchors, as at 127, embedded in the water bed 17. By appropriately actuating the winches 126, the center pile may be adjusted at the water level to the exact location desired, and held there by the anchor lines during driving of the batter piles.

FIGS. 6 and 7 show a modification of the invention wherein the superstructure 10 of FIGS. 1-3 is supported at each of its four corners on a pair of piles, comprising a plumb or vertical pile 1 30 and a batter pile 131. For this purpose a modified type of collar is required for mounting on the superstructure. The modified collar,

shown at C, has substantially the contour in elevation of the numeral 8, the side walls being intended at the middle of the longer axis, as at 132, 133, and having Welded thereto at equi-spaced intervals vertically, a series of strengthening ribs or flanges, as at 134-, which follow the contour of the collar along their inner edges, but have rectilinear outer edges spanning, as at 135, 136, the indented collar portions. Tapped through the collar at spaced points vertically are a series of adjusting bolts, as at 137-146, inclusive, like those of the FIGS. 4 and 5 embodiment.

After the pile pairs are driven and cut off to the proper elevation above the water level as above described, the superstructure mounting the collars C, is lowered into position to enter the pile pairs in the collars respectively, in the manner shown. The bolts are then tightened agm'nst the piles 130', 131.

In this modification, the purpose of imparting the numeral 8 configuration to the collars, is to permit the adjusting bolts to grip each pile over a suflicient circumferential extent of each to hold both firmly in position until the concrete has been poured and set. Thus it will be noted that bolts 140444 grip pile 1 31 on all sides, while the remaining bolts similarly grip pile 130. The straight outer edges v135, 136 of the flanges 134, prevent the indented portions 132, 133 of the collars from being pulled away from the piles.

When the bolts have been thus adjusted, the space between the piles and collars is filled with liquid concrete as previously described. Also the piles are filled with plugs of liquid concrete as above described in which are embedded the tubular bases of steel pedestals, such as 147', to receive the drilling floor as previously described.

The collar construction of FIG. 8 is generally like that of FIGS. 6 and 7 except for being adapted to receive a pair of batter piles instead of one plumb and one batter pile. The collar D is of the numeral 8 contour in plan and braced by flanged ribs as at 150, the inner edges of which follow the collar contour indentations, as at 1, 152, but which have rectilinear outer edges spanning these indentations, as at 153, 154, for reasons above explained. It will be seen that the two sets of adjusting bolts, 155, 156, grip the piles 157, 158 circumierentially thereabout in each instance.

What is claimed is:

1. The method of erecting an offshore structure consisting of a unitary platform mounted on pile ends by means of metal collars integral with said platform and of substantially greater transverse dimensions than said pile ends, said collars having adjusting bolts tapped therethrough at spaced points thereabout, said method comprising: driving said piles at spaced intervals such that their upper ends may be entered into said platform collars,

respectively, lowering said platform into a position such that said pile ends are so entered into the respective collars, maintaining the platform so positioned while adjusting the bolts of each collar to grip on all sides the V pile entered therein, and filling the space between each.

collar and pile end with liquid concrete and allowing the concrete to harden and set.

2. The method of mounting a drilling platform of unitary and rigid construction for oifshore oil drilling and the like, said platform having integral therewith at points spaced about its periphery, a plurality of metal collars disposed substantially perpendicular to said platform and adapted to receive the upper ends, respectively, of a series of supporting piles of substantially smaller transverse dimensions than said collars, each collar having tapped therethrough at spaced intervals, a series of bolts, threadedly adjustable to frictionally engage a pile end entered within said collar for securing the platform thereto and supporting the same thereat, said method comprising:

driving a series of piles at spaced intervals such that their .upper ends may be entered into said platform collars,

respectively, lowering said platform into a position such that said pile ends are so entered into the respective collars and maintaining the platform so positioned while adjusting the bolts of each collar to grip the pile entered therein, filling the space between each collar and pile with liquid concrete, and allowing the same to harden and set.

References Cited in the file of this patent UNITED STATES PATENTS 1,284,565 Bennet Nov. 12, 1918 1,585,254 Lund May 18, 1926 1,617,762 Kiefer Feb. 15, 1927 1,807,962 Cassiere June 2, 1931 2,429,952 Willey Oct. 28, 1947 2,589,146 Samuelson Mar. 11, 1952 2,592,448 McMenimen Apr. 8, 1952 2,651,181 Alcom et al. Sept. 8, 1953 2,653,451 McCullough Sept. 29, 1953 2,667,038 Bayley Jan. 26, 1954 2,736,172 McChesney Feb. 28, 1956 2,775,095 Harris Dec. 25, 1956 2,775,869 Pointer Jan. 1, 1957 2,822,670 Suderow Feb. 11, 1958 2,933,898 Upson Apr. 26, 1960 FOREIGN PATENTS 2,228 Great Britain June 27, 1873 OTHER REFERENCES Civil Engineering, pp. 41-43, July 1956.

Reprint of Civil Engineering magazine article, July 1956, Prestressed Precast Platform Built in Gulf, Robert N. Bruce, Jr.

Claims (1)

1. THE METHOD OF ERECTING AN OFFSHORE STRUCTURE CONSISTING OF A UNITARY PLATFORM MOUNTED ON PILE ENDS BY MEANS OF METAL COLLARS INTEGRAL WITH SAID PLATFORM AND OF SUBSTANTIALLY GREATER TRANSVERSE DIMENSIONS THAN SAID PILE ENDS, SAID COLLARS HAVING ADJUSTING BOLTS TAPPED THERETHROUGH AT SPACED POINTS THEREABOUT, SAID METHOD COMPRISING: DRIVING SAID PILES AT SPACED INTERVALS SUCH THAT THEIR UPPER ENDS MAY BE ENTERED INTO SAID PLATFORM COLLARS, RESPECTIVELY, LOWERING SAID PLATFORM INTO A POSITION SUCH THAT SAID PILE ENDS ARE SO ENTERED INTO THE RESPECTIVE COLLARS, MAINTAINING THE PLATFORM SO POSITIONED WHILE ADJUSTING THE BOLTS OF EACH COLLAR TO GRIP ON ALL SIDES THE PILE ENTERED THEREIN, AND FILLING THE SPACE BETWEEN EACH COLLAR AND PILE END WITH LIQUID CONCRETE AND ALLOWING THE CONCRETE TO HARDEN AND SET.

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