WO2012004235A2 - Method for preventing the escape of environmentally harmful substances in underwater drilling operations and pipe string therefor - Google Patents

Abstract

A description is given of a method for preventing the escape of environmentally harmful substances in drilling operations for the extraction of oil and gas in underwater formations, comprising the steps of producing a pipe string (4) by using large pipes (3) and a tubular cutting sleeve (7) at the bottom end of the pipe string (4), lowering the pipe string (4), held by a float (1), with the cutting sleeve (7) leading the way, down to the formation on the bed (6) of the water, sinking the cutting sleeve (7) into the formation by applying a load, installing a submersible pump (8) in the pipe string (7) and reducing the internal pressure in the pipe string by continuously lowering the filling level below the water level of the water surrounding the pipe string and collecting the pumped-out water in a tank (12).

Description

 Method for preventing the escape of environmentally harmful substances in underwater wells and pipe string therefor

The invention relates to a method for preventing the escape of environmentally harmful substances in wells for recovering oil and gas in submerged formations. The invention further relates to large pipes for producing a pipe string for carrying out the method.

When drilling holes in submerged formations, such as under the sea or a lake, it is known to secure the well at the bottom of the sea or lake with a blowout preventer and the blowout preventer by a protective tube system, called a riser, to connect with the floating device on which the drilling rig or conveyors are arranged. The drill string and delivery lines are routed through the riser and blowout preventer to the wellbore. The disadvantage here is that damage to the preventer or in the area below the preventer of the escape of oil or gas and thereby caused pollution of the sea, lake or the like can not be prevented. The invention has for its object to provide a method which provides greater security against the escape of environmentally harmful substances when drilling in submerged formations.

The object is achieved by the method specified in claim 1. According to the invention, the method comprises the following steps:

a) producing a pipe string using large pipes and a tubular cutting shoe at the foot of the pipe string,

b) lowering the pipe string held by a floating body with the cutting shoe first to the formation at the bottom of the water such that the cutting shoe surrounds the drilling site or the borehole with any facilities present there,

 Sinking the cutting shoe into the formation by loading the cutting shoe with its own weight and the weight of at least a part of the pipe string,

 Installing a submersible pump in the tubing and lowering the internal pressure in the tubing by continuously lowering the level in the tubing below the water level of the surrounding surrounding pipe string by pumping existing and inflowing medium from the tubing into a collection container.

In the method according to the invention, the cutting shoe and the lower end of the tubing surround an area surrounding the borehole at the bottom of the water or the sea and any facilities there including blowout preventer and riser pipe.

Furthermore, in the water-filled pipe string by lowering the filling level, a negative pressure is generated, so that it can only come to an inflow, but not to a leakage of liquid medium in the entire region of the pipe string. In this way, it is ensured with great certainty that even with damage to the drilling rig or the delivery lines no oil can escape to the outside when they are passed through the pipe string to the bottom. Even if there is a leak on the pipe string, it can only lead to the ingress of water into the pipe string, which can be compensated up to a repair by a corresponding increase in the discharge capacity. Furthermore, the method according to the invention offers the advantageous possibility of arranging a device for outbreak prevention at the upper end of the pipe string and thus over water. The method according to the invention is equally suitable for combating an accident in a subsea drilling system, for example by breaking a Bohroder conveyor line. For this purpose, the pipe string from large pipes can be drained above the damaged area and guided with the aid of robot and camera in such a way that the cutting shoe surrounds the damaged area. The cutting shoe deposited at the accident site is then pressed into the pending seabed by the weight of the pipe string or part thereof. According to the method, the internal pressure is then lowered by lowering the level in the tubing by about 2 to 3 bar, which can no longer flow into the open sea at the disaster point emerging oil, but rises within the tubing and can be pumped off together with inflowing water.

According to another proposal of the invention, the large pipes of the pipe string are limited axially movable connected to each other. This ensures that even with a ground fault on the seabed, the cutting shoe of the pipe string can automatically reset. Furthermore, the load of the cutting shoe can be varied with the aid of the movable connection by means of defined lowering of the upper end of the tubing string held by the floating body.

In order to be able to limit the load on a device arranged on the floating body for lifting, lowering and holding the pipe string, according to a further proposal of the method according to the invention, at least a part of the pipes of the pipe string can be connected to a buoyant body. Furthermore, it can be provided that the upper end of the pipe string is movably mounted on the floating body in the vertical direction. As a result, vertical movements of the float can be compensated by sea state and thereby limited forces on the pipe string can be limited. To produce the pipe string, according to a further proposal of the invention, large pipes are used which comprise an outer pipe, an inner pipe concentrically arranged in the outer pipe and pressure-tightly connected at its ends to the outer pipe by ring walls, and a pipe formed between the outer pipe and the inner pipe hollow annulus have. The large pipes thus constructed have a high rigidity and thus withstand high pressure and bending loads. The hollow annulus forms a buoyant body which reduces the tube weight in the water to about 80%. The annular space can according to the invention have valves for flooding and emptying. By completely or partially flooding the annulus with water, the tube weight can be increased more or less. This also makes it possible to change the load on the cutting shoe.

Furthermore, it is advantageous if in the annular space, the inner tube with the outer tube connecting stiffeners are arranged. The stiffeners may consist of extending parallel to the tube axis strips or profiles.

According to a further proposal of the invention, the large pipe at its pipe ends matching counterparts of a pipe connector, wherein the one pipe end has a pipe sleeve and the other pipe end connectable with such a pipe socket pipe spigot and the pipe sleeve on its inside and the pipe pin on its outside in the same Separation distance from one another along a circumferential line have a plurality of support elements, which cooperate in the manner of a bayonet connection with the support elements of a correspondingly shaped pipe pin or a correspondingly shaped pipe sleeve to connect the respective pipe end with a matching counterpart at the pipe end of a second appropriately designed large pipe. Such a pipe connector is described in EP 0 705 405 B1, the contents of which are hereby incorporated by reference. Such a pipe connector has proven itself in practice in the implementation of civil engineering work. It can transmit very high forces and be easily assembled and released. In the connection position of the pipe connector is reliably locked by a releasable securing element.

Preferably, the pipe connector according to the invention in the axial direction on a movement play, which can be up to several centimeters. Due to the play of movement of the pipe connector, the axial length of the pipe string can vary and thereby compensate settlement of the cutting shoe and vertical movements of the float.

At the lower end of the pipe string according to the invention a tubular cutting shoe is arranged with a circular cutting edge. The cutting shoe, which consists of a thick-walled pipe, preferably has an inner diameter which is at least equal to the inner diameter of a large pipe connected to the cutting shoe. To carry out the method according to the invention, it is not absolutely necessary that the pipe string is formed over its entire length from large pipes. For example, it may be useful in combating an accident at a greater depth, if a portion of the pipe string has a smaller inner diameter than the large pipes, wherein at the transition between the section and the adjoining large pipe, a reducer is arranged.

The invention will be explained in more detail with reference to embodiments. Show it FIG. 1 shows an application example of the method and the device according to the invention,

 2 shows a side view of a large pipe according to the invention and FIG. 3 shows an end view of the large pipe according to FIG. 2,

Figure 4 shows another example of the method and the

 Device according to the invention.

In the application shown in FIG. 1, the oil and gas emerging from a production well bore at a marine site on the seabed are collected by means of the method according to the invention and controlled to be transported overground, where it can be disposed of in the usual way or further processed. In this application, from a float 1, such as a pontoon or ship, by a keel tube 2 of the float 1 on the float 1 with the aid of suitable facilities gradually from large pipes 3 composite pipe string 4 using suitable lifting devices to a failure point 5 on the seabed. 6 lowered. At the lower end of the pipe string 4, a cutting shoe 7 is arranged, which consists of a thick-walled tube having the same outer diameter as the large pipes and an inner diameter which is larger than the inner diameter of the large pipes. Alternatively, a cutting shoe with larger dimensions, e.g. in the manner of a bell, are used when a larger area is to be covered at the accident location of the cutting shoe. The cutting shoe 7 has at its lower end an inlet opening which is surrounded by a cutting edge formed by its wall.

During the lowering of the pipe string 4, the large pipes 3 hang with their reduced by buoyancy weight to each other, which sets due to the design of the pipe connector at the joints a maximum axial play, which may be a few millimeters or centimeters depending on the design. When lowering the pipe string 4, the cutting shoe 7 is guided by means of robots and underwater cameras so that it passes over the damaged area 5. If the cutting shoe 7 deposited on the seabed 6, it is burdened by further lowering the tubing 4 with the weight of a series of large pipes 3, which gradually put on each other, the axial clearance disappears at the joints. As a result of this load, the cutting shoe 7 penetrates deeper into the seabed 6 and thereby closes the damaged area 5 better. In addition, the inflow of water is counteracted.

While the cutting shoe 7 digs into the seabed 6, at the same time with the aid of a submerged in the tubing 4 submersible pump 8, the penetrated into the tubing 4 water and oil pumped in such an amount that the level 9 within the tubing 4 about 20 to 30 m below the level of the sea level 10 drops. This has the consequence that the internal pressure in the pipe string is 2 to 3 bar below the pressure of the sea. From the area enclosed by the cutting shoe 7 and the area adjacent to the opening of the cutting shoe 7 area escaping oil, gas and water is therefore sucked into the cutting shoe 7 and the tubing string 4 and flows in the tubing string 4 upwards. Since the internal pressure in the tubing 4 at any point is less than the pressure of the surrounding the tubing 4 water, even leaks in the tubing 4 can not lead to leakage of oil or gas. At the upper end of the tubing 4 and the sucked oil and water are conveyed by means of submersible pump 8 via a riser 1 1 in a collecting container 12, from which they can be removed for separation and further treatment by suitable means. The rising gas is sucked off with the aid of a suction device 13, which is connected to the upper end of the tubing 4. The lifting, lowering and holding of the pipe string 4 can be carried out in a simple manner by means of a device arranged on the float 1, as described in DE 1 97 21 635 C2. However, other suitable lifting equipment can be used for this purpose. The holding of the tubing string 4 on the floating body 1 can be done with the aid of a hydraulic interceptor 1 4, which operates semi-automatically and is similar to a wedge pot formed in a rotary table. When lifting or lowering the lowering speed of the pipe string can be measured with an optical measuring device. If a predetermined maximum value of the lowering speed is exceeded, then the interceptor 14 is automatically closed. On the floating body 1, the pipe string 4 holding support device 14 is advantageously supported by means of springs 15 movable in the vertical direction, so that vertical movements of the float 1 can be compensated. Other, for example, hydraulic devices for compensating movement can also be provided.

The large pipe 3 shown in FIGS. 2 and 3 for forming the pipe string 4 has a cylindrical outer pipe 30 and a cylindrical inner pipe 31 arranged concentrically therein. The longer outer tube 30 is connected to the inner tube 31 with conical annular walls 32 arranged at the ends of the inner tube 31. Between the outer tube 30 and the inner tube 31 is an annular space 33 in which pairs of stiffening strips 34 are arranged at a regular circumferential distance. Each pair has two V-shaped stiffening strips 34, which are arranged so that they extend from a common attachment point on the inner tube 31 from diverging to two attachment points on the outer tube 30. The stiffening strips 34 extend in the longitudinal direction parallel to the axis of the tubes and have the same length as the inner tube 31st The lower end in the drawing of the outer tube 30 is extended beyond the annular wall 32 and forms with the extended portion of a pipe sleeve 35, which is provided on its inside a plurality of rectangular support members 36 which are arranged at a regular distance from each other and about their Have circumferential length corresponding distance from each other. Adjacent to the annular wall 32, a support ring is further secured in the pipe sleeve 35, which has a distance from the support elements 36.

In the upper end in the drawing of the outer tube 30, which also protrudes beyond the annular wall 32, a pipe section 37 is inserted, which forms a protruding from the outer tube 30 pipe spigot 38. The pipe spigot 38 is on its outside in the same way as the pipe socket 35 with a multiplicity of parallelepipedal support elements 39 which are at the same distance from each other as the support elements 36 and can be pushed back between the support elements 36. In this way, the two ends of the large pipe 3 are provided with matching counterparts of a pipe connector, which can be connected by axial nesting and mutual rotation by a distance corresponding to the distance between the support members 36, 39, as described in detail in EP 0 705 405 B1 , The connection position is locked by a securing element that can be mounted from the outside through a window 40 in the pipe sleeve 35.

The annular walls 32 each have an opening 41, in which a flood valve or a drain valve is used or which can be closed with a stopper. If the annular space 33 remains empty, it forms a buoyant body, which reduces the weight of the pipe in the water. If the effect of the buoyant body omitted or reduced, the annulus can be completely or partially filled with water via the valves used. Figure 4 shows an application of the method and associated apparatus to a deep well at the bottom of a sea or inland water. The process has the task of protecting the sea or inland waters from contamination by the drilling process and possible damage to the drilling or conveying equipment. As described above in connection with Figure 1, prior to sinking the bore, a tubing string 4 of large pipes 3 is lowered from a floating body 1 to the ground to be drilled and anchored to the bottom of the pipe string cutting shoe 7 in the ground by ramming. If required, the anchoring of the cutting shoe 7 with the lower pipe end can be done additionally by cementing. If the pipe string 4 is sunk and anchored, the water level in the pipe string 4 is lowered by a few meters below the water level of the surrounding water body by a lowered into the tubing 4 submersible pump 8 and held at this lowered level. In the shelter space 19 formed by the pipe string 4, drill pipes, such as a riser strand 20 and a drilling or production string 21, can now be guided to the lower anchoring end of the pipe string 4. The riser strand 20 can be anchored in the usual way in the bottom of the well or by means of a suitable latching device in the lower end of the tubing 4. With the help of the drill string 21 having at its lower end a drill bit and possibly a drill motor, then the sinking of the deep hole.

At the upper end of the tubing string 4, the drill pipes are passed through a cover plate 16 which is mounted on the upper Rohrstrangende. The cover plate 16 has a guide tube 1 7, in which the riser strand 20 is guided and supported. At the upper, protruding from the guide tube 17 end of the riser strand 20, a device 22 for outbreak prevention (blowout preventer) is arranged, which closes the end of the riser strand 20 and forms a secure passage for the drill string 21. This arrangement of the device 22 is due to the protected arrangement of the drill pipes within the tubing 4 allows. It has the advantage of easy and inexpensive installation, maintenance and control of the device 22, which increases safety. If, during the drilling operation, environmentally damaging substances escape from the drill pipes, they are taken up by the protective space 19 formed by the pipe string 4 and can be removed therefrom by being pumped out. A leakage of pollutants from the tubing 4 is not possible due to the lower ambient pressure compared to the internal pressure in the shelter 19 even if the tubing 4 is leaking at one point.

Claims

A method for preventing the escape of environmentally harmful substances in wells for recovering oil and gas in submerged formations comprising the steps of:  a) producing a pipe string (4) using large pipes (3) and a tubular cutting shoe (7) at the foot of the tubing string (4),  b) lowering of a float (1) held pipe string (4) with the cutting shoe (7) first to the formation at the bottom (6) of the water such that the cutting shoe (7) surrounds the drilling site or the borehole with any facilities there,  c) sinking the cutting shoe (7) into the formation by loading the cutting shoe (7) with its own weight and the weight of at least a part of the pipe string (4),  d) installing a submersible pump (8) in the tubing (4) and lowering the internal pressure in the tubing (4) by continuously lowering the level in the tubing (4) below the water level of the tubing (4) surrounding water by existing and inflowing Medium from the tubing (4) is pumped into a collecting container (12). A method according to claim 1, characterized in that the large pipes (3) of the pipe string (4) are limited axially movable connected to each other. 3. The method according to any one of claims 1 or 2, characterized in that at least part of the large pipes (3) of the tubing string (4) are connected to a buoyant body. 4. The method according to any one of the preceding claims, characterized in that the upper end of the tubing string (4) in the vertical direction is movably mounted on the floating body (1). 5. The method according to any one of the preceding claims, characterized in that when drilling a hole, the drill pipes through the pipe string (4) of large pipes (3) are guided and that a device (22) for outbreak prevention (blowout preventer) at the top of the Pipe string (4) is placed over the water level. 6. tubing for performing the method according to any one of the preceding claims, characterized by at least one large tube (3) having an outer tube (30), in the outer tube (30) concentrically arranged inner tube (31), which at its ends by Ring walls (32) pressure-tight manner with the outer tube (30) is connected, and between the outer tube (30) and the inner tube (31) formed hollow annular space (33). 7. Pipe line according to claim 6, characterized in that the large pipe (3) valves for flooding and emptying of the annular space (33). 8. Pipe strand according to one of claims 6 or 7, characterized in that in the annular space (33) of the large tube (30), the inner tube (31) with the outer tube (30) connecting stiffeners are arranged. 9. tubing according to claim 8, characterized in that the stiffeners consist of parallel to the tube axis extending strips (34) or profiles. Pipe string according to one of claims 6 to 8, characterized in that the large pipe (3) has at its pipe ends counterparts of a pipe connector, wherein the one pipe end a pipe sleeve (35) and the other pipe end with such a pipe socket (35) connectable pipe spigot (35) 38) and the pipe sleeve (35) on its inside and the pipe spigot (38) on its outer side at the same pitch from one another along a circumferential line a plurality of supporting elements (36, 39) which in the manner of a bayonet connection with the supporting elements (36, 39) of a correspondingly shaped pipe pin (38) or a correspondingly shaped pipe sleeve (35) cooperate to connect the respective pipe end with the matching counterpart at the pipe end of a second appropriately designed large pipe (3). Pipe strand according to claim 10, characterized in that the pipe connector can be locked in the connecting position by a releasable securing element. Pipe strand according to one of claims 10 or 11, characterized in that the pipe connector has a play of motion in the axial direction. Pipe strand according to one of claims 6 to 12, characterized in that at the lower end a tubular cutting shoe (7) is arranged with a circular blade whose inner diameter is at least equal to the inner diameter of at least one connected to the cutting shoe large pipe (3). Pipe string according to claim 13, characterized in that it comprises a portion having a smaller inner diameter than that at least one large pipe (3), wherein between the portion and the at least one large pipe, a reducer is arranged. Pipe string according to one of claims 6 to 14, characterized in that the upper end has a guide and support for through the pipe string (4) guided drill pipes. Apparatus for carrying out the method according to one of claims 1 to 5, characterized by a floating body (1), a pipe string (4) made of large pipes (3), arranged on the float lifting device with lifting and holding devices (14) for lifting and holding the large pipes (3), a power supply device, a submersible pump (8) which can be lowered into the pipe string (4) and a collecting tank (12) which can be connected to the outlet of the submersible pump (8). Apparatus according to claim 16, characterized in that at the upper end of the tubing string (4) a cover plate (16) is arranged with a penetrating this guide and support for imported from above into the tubing drill pipes. Apparatus according to claim 17, characterized in that above the cover plate (16) on the drill pipes, a device (22) for outbreak prevention (blowout preventer) is arranged.