RU2531694C1 - Mounting of screw-fit pile anchor - Google Patents

Abstract

FIELD: oil-and-gas industry.

SUBSTANCE: invention relates to development of oil and gas deposits and can be used for anchoring of mining equipment at sea bottom. Proposed method comprises fitting the pile anchor in place by screwing the cylinder in soil, well drilling via wellhead, lowering of reinforced well casing in the well and cementing the string inner space. Note here that casing pipe is pre-furnished with lengthwise sawcuts. Prior to cementing of casing string, charge is lowered to 1.5-2.0 m from well bottom to explode its so that inverted plume is formed in the area if sawcuts as well as cavities in soil to be filled with concrete.

EFFECT: higher reliability of retention.

3 dwg

Description

The invention relates to methods for developing underwater, mainly marine liquid and gaseous deposits, in particular, to methods for fixing mining equipment on the seabed by means of anchors.

Known screw-piling pile anchor for floating structures in the sea, mainly floating platforms for oil and / or gas production, including a hollow cylinder with an external thread and a limiter mounted on the thread, an anchor docking station with a rack, an anchor chain attachment unit, and also installed in the upper part inside the cylinder along its axis there is a small cylinder with an external thread (mouth), as well as exhaust valves. In addition, the anchor includes a pile from a string of reinforced casing, made with the possibility of fastening to the mouth. The housing is made with the possibility of deepening into the seabed, for which teeth are made on the end surface of the housing. A threaded cylinder is installed on the outer surface for screwing into the seabed. The armature is provided with a concreted in the well casing, passing through threaded cylinder (see. Utility Model "MARINE AUTONOMOUS SYSTEM FOR OIL, semi-submersible floating drilling platforms, marine mining RACK pumping oil, ice resistant FLOATING PLATFORM FOR OIL, ledostojkih FLOATING TANK FOR COLLECTING AND OIL STORAGE. ANCHOR FOR FLOATING STRUCTURES IN THE SEA "according to RF patent No. 86231, application: 2008135989/22, 05.09.2008).

As a prototype, the method of installing such an anchor is selected, which consists in screwing the cylinder into the ground to the limiter, drilling the well through the mouth, lowering the reinforced casing pipes into the well, and pouring concrete into the cavity of the column.

The indicated method of installation and fastening of the screw-anchor anchor does not provide reliable retention of floating structures during strong storms or in an encounter with an iceberg.

The objective of the present invention is to increase the reliability of the retention of floating structures relative to the seabed during storms, collisions with icebergs and moving ice fields.

This problem is solved due to the fact that in the method of installing a screw-pile pile anchor by screwing the cylinder into the ground to the limiter, drilling the well through the mouth, lowering the reinforced casing pipes into the well, pouring concrete into the cavity of the column, according to the invention, the lower casing is preliminarily provided with longitudinal cuts, before pouring concrete into the casing string at a distance from the bottom of the well 1.5-2.0 m lower the charge and undermine the charge with the formation in the area of cuts inverted with Ulthan and the formation of caverns in the ground, while the cavity is also filled with concrete.

A significant increase in the reliability of anchor fastening is provided by the creation of a concrete block placed inside the soil of the seabed, while the dimensions in terms of concrete blocks significantly exceed the similar dimensions of the other parts of the anchor. In the explosion, the lower casing is destroyed in the zone where the longitudinal cuts are made, the pipe breaks and its longitudinal elements are bent to the sides in the form of feathers of the sultan. The injected concrete covers these curved longitudinal elements and, when solidified, acquires the quality of a metal-reinforced concrete monolith. In addition, the explosion not only ensures the creation of an underground cavity, but significantly compacts the walls of the formed cavity, providing a closed cavity without gaps, which prevents excessive consumption of concrete.

The invention is illustrated by drawings, where Fig. 1 shows a diagram of the fastening of a floating ice-resistant drilling platform by means of anchors, Fig. 2 - screw-anchor anchor, Fig. 3 - screw-anchor anchor with a stand (pile).

An oil rig 1 mounted on a platform 2 having the shape of an icebreaker skirt. The platform 2 is equipped with pontoons 3 and is connected through chains 4 with screw-anchor anchors.

The anchor device structurally consists of two parts: screw-anchor anchor and anchor strut 5. The screw-anchor anchor is a hollow cylinder 6 made of strong steel, closed on one side. On the outer surface of the cylinder 6 there is a thread. The diameter of the cylinder is 2 m, the length is 20 m. In the center, on the closed side, there is a small cylinder 7, with a diameter of 0.5 m, and a length of 4 meters. She also has a thread on the outer surface. On the closed side there is an attachment unit 8 of the anchor chain 4, a threaded docking assembly 9 of the anchor with the strut 5, exhaust valves 10. At the end of the screw-anchor anchor, the stopper 11 is screwed onto the thread. When the post 5 is lowered, the stopper 11 is first immersed in the ground and then through him, the hollow cylinder 6 is screwed into the bottom soil.

Anchor pile 5 is a column of powerful pipes with a diameter of 0.35 m and a length of 100-150 m. The wall thickness is 0.07 m.

Thus, the screw-suction pile anchor includes a hollow cylinder 6 with an external thread and a stop 11 mounted on the thread, a docking node 9 of the anchor with a rack 5, an anchor chain attachment unit 8, and also a small cylinder 5 s installed in the upper part inside the cylinder 6 along its axis external thread (mouth), as well as exhaust valves 10, in addition, there is a pile 12 of a string of reinforced casing, made with the possibility of fastening to a small cylinder 7 (mouth), longitudinal cuts are made on the bottom of the last casing of pile 12 (not showing any). The length of the cut corresponds to half the length of the casing.

The screw-anchor anchor is attached to a special rack 5, on a floating platform 2. As the rack 5 is mounted, the anchor, using special mechanization, lowers to the bottom. As soon as the limiter 11 stops on the bottom soil, the post 5 begins to rotate using a special rotor. The mass of the strut 5 presses the anchor with certain efforts and helps the anchor to easily screw into the bottom. As soon as cylinder 6 (anchor) is completely screwed into the bottom soil, the rotation stops. In the process of screwing in, the liquid that has entered the cavity between the outer surface of the central pipe 7 and the inner surface of the main pipe - cylinder 6 (annular gap) is evacuated through the outlet valves 10. When trying to raise the screw-anchor anchor installed at a depth of 200 m, hydrostatic pressure will exert resistance of 600 TC. Then, through the stand 5, inside which there is a column of process pipes, the drilling tool is lowered and a well with a diameter of 0.4 m is drilled through the central, small cylinder. The central small cylinder 7 in this case plays the role of the mouth.

Well 16 is drilled to a depth of 100-150 m. Then pile 13, like a casing string, is lowered into the well and fixed at the mouth 7. The pipes that make up pile 13 are 10 m long. Half of the lowest pipe has longitudinal cuts along the entire circumference every 8-10 cm. After the pipe has lowered into the well, a charge of a certain power is lowered into it. At a height of 1.5 m above the bottom of the well, on command from the platform, it is blown up. Excessive pressure from the explosion breaks the pipe along the cuts, forming an inverted "sultan" of steel leaves. The explosion also forms a volume cavity 13 at the end of the well, called a “cavity”. The volume of the cavity is 6-8 m ³ . From experience it is known that from excess pressure, the inner surface of the cavity is significantly compacted. Then, in pile 12, and hence in the cavity, concrete 12 is pumped under pressure until the entire pile 13 is filled. In the concrete 12 of the cavity, steel sheets 14 of the broken pipe turn out to be. After the hardening of concrete, they form a reinforced concrete block 15, repeating the volume of the cavity. It is recommended to use heavy grades of concrete, for example, barite, for these purposes. This ensures reliable fastening screw screw pile anchor

Operational characteristics of screw-screw, pile anchor.

Chain 4 can be attached to any floating marine object and the screw-anchoring pile anchor will hold it. It is not possible to pull out a pile anchor, with reinforced concrete block 14 at the end from 100 m depth, by any natural elements, including storms, moving ice fields and even Arctic icebergs. It is advisable to use a chain of increased strength. The thickness of the link bar is 150 mm. The resulting heavy chain can be lightened with cylinders 15 filled with a special lightening mixture, for example, a mixture of broken glass and epoxy or another more modern mixture. Such a circuit can withstand a break of more than 7000 Tc. The specified chain can stop the Arctic iceberg weighing up to 2 million tons or more. French scientists at one time made a mathematical model for towing an iceberg weighing 7 million tons. According to their calculations, such an iceberg had to tow one tug! And only 20 atomic icebreakers of the “50 Years of Victory” type, the most powerful in the world with a thrust of 350 Tc, can create an effort of 7000 Tc. Together they can stop any, even the Antarctic iceberg, let alone a small Arctic iceberg. In addition, the drift velocity of Arctic icebergs is extremely low, not more than a few cm per second, due to the lack of fast surface currents in the Barents Sea. In the literature you can find that the drift velocity of Arctic icebergs is 25 cm per second. This means that the daily drift speed is 50 miles. This is indicated the highest speed, which takes place only in the area of the Greenland current. In the rest of the Arctic, including the Barents Sea, the daily speed of icebergs does not exceed several miles. This means a few centimeters per second!

The screw-anchor pile anchor is designed to mount ice-resistant floating drilling platforms on the Arctic shelf, as well as anywhere in the world ocean at depths of 100 m and deeper that produce hydrocarbons, for example, at the Shtokman gas condensate field.

Claims (1)

Method of installing screw-pile pile anchor by screwing the cylinder into the ground to the limiter, drilling a well through the mouth, lowering reinforced casing pipes into the borehole, pouring concrete into the cavity of the casing, characterized in that the lower casing is provided with longitudinal cuts before pouring concrete into the casing string at a distance from the bottom of the well 1.5-2.0 m lower the charge and undermine the charge with the formation in the area of cuts inverted sultan and the formation of a cavity in the ground, while concrete ie filled cavity.

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