HK1096551B - System, tank and output unit for transporting untreated drill cuttings - Google Patents

Abstract

System for transport of untreated drill cuttings, comprising a tank (2). The tank (2) is arranged below the deck of a ship (1) and has an output unit (10) at the bottom (6), to feed the drill cuttings towards an output opening (8). A pump (21) is provided below the bottom of the tank (2) to feed the drill cuttings through an unloading line (13). The unloading line (13) has a substantially uniform cross section and is shaped so that the velocity of the flow close to the inner wall is substantially equal in the same cross section. The tank (2) has an upper circular cylindrical part (3) and a lower frustuconical part (4) and a substantially flat bottom (6). In the flat bottom (6) is an output opening (8), which extends from the side wall (5) of the frustuconical part (4) to an inner dome or cone (11).

Description

System, tank and output device for transporting untreated drill cuttings

The present application relates to a system for transporting untreated drill cuttings. By "untreated" it is meant that the drill cuttings have not undergone any effective treatment, such as by the addition of a liquid, in order to make them useful for transportation.

During the production of oil and gas, drilling a well produces a large amount of drill cuttings. These cuttings include rock, water and residues of various chemicals used as additives in the drilling process. Drill cuttings also contain hydrocarbons, such as oil.

Initially, the cuttings are simply disposed of on the seabed. However, researchers have found that drill cuttings can severely damage the environment and have a significant impact on spawning of deep-sea fish, among other things. Many countries today therefore no longer allow for dumping of drill cuttings onto the seabed in vulnerable areas. Thus, the cuttings must be transported to shore for disposal or, alternatively, for grinding or re-injection. On shore, drill cuttings are disposed of in an environmentally friendly manner. Several treatment methods are also included, wherein a portion of the drill cuttings may be commercially utilized before disposal of the remaining waste water.

There are many systems for separating drill cuttings from downhole drilling fluids. Examples thereof are described in patents NO311232, NO312915, NO19985493, NO19991798, US2001/0039887, GB 2350851.

A system for removing dumped drill cuttings from the seabed is also known from WO 01/38648.

The systems currently used for transport are highly labour-intensive and the number of cranes participating in the system is often unsatisfactory, in particular the number of drilling rigs. The systems on the supply vessel are also labor intensive and take up space. No new proposals have been made for systems that can transport untreated drill cuttings under deck in a satisfactory manner. At present, the most common mode of transport is the filling of drill cuttings into open trolleys on drilling platforms (or vessels), as described in US5971084, US20032400 (corresponding to US6585115), WO03/095789 and NO 19995270. The skip is then lifted by the crane onto the supply vessel. The skip is then transported to a shore reception plant on the deck of the supply vessel. Such deck transport is considered unsafe. If the supply vessel encounters stormy weather, the skip is at risk of being engulfed by seawater, either by intentional and sudden inclination, or by negligence of work. It is therefore highly desirable to be able to transport drill cuttings under the deck.

The cuttings are very viscous. Attempts have been made to transport the drill cuttings in a tank containing an agitator to keep the drill cuttings as liquid as possible. However, this causes the drill cuttings to be partially converted into a concrete-like mixture, which cannot be pumped. The transport of the skip is of little significance, since the skip can be emptied more or less by turning them upside down. However, when using a ship tank, this is not possible and the stoned cuttings prove to be almost impossible to remove. It has also been proposed to add liquid in order to keep the drill cuttings liquid. However, this does not solve the problem, and in addition to this, large amounts of liquid must also be delivered. The above examples are described in US6345672 and GB 2330600.

NO20021070 proposes the use of a tank towed behind a ship for transporting drill cuttings. If the can is detached and drifts away, there is a consequent risk of contamination.

Although US6345672 and GB2330600 propose solutions to the problem, the present invention is still based on the use of tanks arranged under the deck, for example the deck of a supply vessel, to transport the drill cuttings. Unlike previous attempts, the present study led to the conclusion that: the design of the tank and output mechanism has a large impact on whether the cuttings can be transported from the tank. When trying to find a solution to the transport problem, either during the actual transport or when feeding the drill cuttings from the tank, the stirring first has proved to have a very negative effect on the viscosity of the drill cuttings. The greater the degree of agitation of the drill cuttings, the greater the degree of lithification of the drill cuttings. This is because the particles within the drill cuttings are locally compressed, resulting in water displacement and an increase in particle density. It is therefore an object of the present invention to avoid any agitation of the drill cuttings to the maximum extent.

Another possible solution is to dry the drill cuttings prior to conveying to allow them to be conveyed in powder form. However, such drying requires a lot of energy and time to perform, resulting in an increase in the space required on the platform of the ship for storage.

In order to successfully achieve the above object, tanks have been given a suitable design in which the cuttings are conveyed towards the tank outlet with minimal agitation and the output mechanism is designed so that the cuttings are agitated as little as possible during the feed-out process.

According to a first aspect, the general idea of the invention comprises a tank, an output mechanism, a controlled gate valve and a pipe down into a pump feeder car. The whole system is implemented as follows: a system for transporting untreated drill cuttings, comprising a tank for containing drill cuttings during transport, the tank having an output means at the bottom of the tank for transporting the drill cuttings out of the tank by pushing the drill cuttings towards an output opening on the bottom of the tank, wherein the tank is arranged below the deck of a ship and comprises a substantially cylindrical upper part and a frustoconical lower part terminating in a substantially flat bottom, the side wall of the frustoconical lower part extending at an angle between 20 ° and 45 ° towards the flat bottom and the flat bottom having an inner dome or cone concentrically arranged against the flat bottom, and a displacement pump arranged at a lower level than the bottom of the tank for receiving the drill cuttings and transporting the drill cuttings forward through a discharge line having a substantially constant cross-sectional area and being shaped such that the drill cuttings flow through the same cross-sectional area The flow velocity is substantially the same near the inner wall of the discharge line and the flat bottom comprises an outlet opening extending from the side wall of the lower part of the frustum cone towards the inner dome or cone.

A second aspect of the invention provides a tank for transporting drill cuttings which achieves the desired effect by features of: the output opening extends from the sidewall of the frustoconical lower portion towards the inner dome or cone.

A third aspect of the present invention provides an output mechanism which achieves the intended effect by the features: at least one arm extends from the hub to the circumference of the flat bottom.

Preferably, the pump has an independently variable speed feed screw. It is also possible to add a liquid containing chemicals and to perform air blowing.

Preferably, the operation and output of the pump is controlled by pressure, speed and torque, and the position of the cuttings in the feeder car is monitored and dry running is avoided.

The invention will be described in more detail with reference to the accompanying drawings, in which:

figure 1 is a longitudinal cross-section of a part of a vessel containing a cuttings tank according to the invention;

FIG. 2 is a top view of the vessel portion and tank;

FIG. 3 shows two canisters according to the present invention with associated output pumps and tubing;

figure 4 shows an output mechanism according to the invention and an output pump for a canister according to the invention;

FIG. 5 shows a pump for a tank according to the invention, and a feed wagon and a valve according to the invention;

FIG. 6 shows a section through an output mechanism according to the invention;

FIG. 7 shows a more detailed cross-sectional view through a portion of the output mechanism; and

fig. 8 shows a hydraulic diagram and a pump for an output mechanism according to the invention.

Fig. 1 and 2 show a vertical section and a horizontal section, respectively, of a vessel 1 in which a plurality of tanks 2 according to the invention are arranged. Preferably, each tank has a circular cross-section, the upper part 3 of which is cylindrical and the lower part 4 forms a frustum of a cone with a side wall 5 extending at an angle between about 20 ° and 45 ° towards a circular flat bottom 6. The shape of the tank is a combination of considerations in making full use of existing space and in the process of outputting, trying to minimise agitation when material is being carried out through the opening in the base 6 of the tank 2. Maximum utilization of the existing space is achieved by designing the cans with a rectangular cross section and having their straight side walls against each other. But this does not result in an efficient output of material, since a large amount of material will remain in the lower corners of the tank. A cylindrical shape (e.g., with a straight sidewall) will also leave material in the lower portion of the can against the sidewall.

The most efficient output can be achieved by a tank having a conical shape with an output opening at its conical tip. The steeper the conical wall, the easier the output process can be carried out. However, such tanks do not make full use of the available space.

The result of the compromise between making the best use of space and obtaining the best output is to have a cylindrical upper part and a conical lower part. It has been found that the frustoconical shape provides sufficient output capacity while increasing the height available for the cylindrical portion.

The total height H that can be utilized is determined by the distance between the bottom 70 (inner double bottom) and the deck 81 of the vessel. This height H can vary from vessel to vessel and within the same vessel. From this height, the entire height h of the pump device below the tank is deducted₁. The height between the deck 81 and the top cargo rail 80 is h₂For connecting hoses, feed nozzles or the like.

The diameter D of the cylindrical part 3 of the tank should be 3 meters minimum. It is not advantageous to use a smaller diameter than this. The diameter does not exceed half the width of the ship, since this is less efficient in utilizing the available space. Currently, 7 meters is considered the largest diameter that can be implemented.

In order to ensure a satisfactory output of the material to be conveyed, the width of the output opening 8 (see fig. 4) should be at least 300 mm. However, it is believed that outlet openings larger than 600 x 800 cannot be implemented because it is difficult to design a valve with an opening larger than this that can simultaneously withstand the weight of the material contained in the tank. The valve may be rectangular as shown, and may alternatively be circular or oval.

Referring briefly to fig. 4, there is shown an output device 10 positioned immediately above the flat bottom 6. In this figure, the tank wall 5 and the upper part 3 are not shown. The output means 10 will be described in detail below, but reference will be made here to the fact that the output means 10 generally have a conical portion 11 which occupies a small portion of the volume of the tank 2. The angle of the conical portion is approximately equal to or steeper than the angle of the side wall 5. Due to this conical shape 11, only the outer part of the bottom 6 is in contact with the material contained in the tank 2. The width b of the outer part should be almost equal to the width of the opening 8. The opening 8 may be rectangular or circular.

The above limitations will ensure that the shape of the can is defined almost uniquely. The difference in shape can lead to poor space utilization or to a complicated material output process.

Figure 3 shows in more detail two tanks 2 with pumping devices 12. A filling device 9 is shown connected to one of the tanks 2. The filling may be performed from one or more similar tanks on the drilling platform or the drilling vessel. Alternatively, filling may be carried out by means of a skip or a large filling bag to a hopper (not shown) above the empty filling plant 9. The filling device may be common to all tanks on the supply vessel 1 and may be moved from one tank to another, or there may be a separate filling device 9 for each tank.

The pumping device 12 will be described in more detail below. From the pumping device 12 the material is transferred into a pipe or hose 13 or a combination of pipes or hoses. The tube or hose 13 has as little internal diameter variation as possible. Furthermore, it should not have too much or too much abrupt bending. This is to avoid water being carried out of the cuttings, making it difficult to transport the cuttings through the pipe 13. The pipe 13 is connected to a receiving device (not shown) on the beach comprising a skip, a large charging bag, a tank or a landfill.

Figure 3 also shows a system 14 for introducing air into the side wall 5. It can be done by means of a blast, especially at the very beginning of the output process, in order to make it easier for the output device to move the material.

Fig. 4 shows the output device 10, arranged against the flat bottom 6. It has a cone or dome structure 11 which is designed to be rotatable. Preferably, the cone is at the same angle as the side wall 5 of the conical part 4 of the can. On the dome 11, there are output arms 15, 16. The two arms extend down the cone 11, along the flat bottom 6 and up the side wall 5. Preferably, the arms 16 are arranged diametrically opposite to balance the forces exerted on the output device. It is also possible to use only one arm 16 or to use more than two arms 16. The arms 15 also extend down the cone 11 and along the base 6 but terminate at the circumference of the base 6. The cone 11 does not have to be conical and may have any dome shape to ensure that the material moves down towards the flat bottom 6.

A sliding track (not shown) may be provided in order to reduce friction between the arm and the side wall of the conical portion, the track extending substantially in the direction of rotation of the arm.

Preferably, the arms are formed with their leading edges closer to the base so as to form a gap between the arms and the base, which gap widens in the direction of the trailing edges of the arms. This helps to avoid wedging of particles between the arms and the base.

Fig. 4 shows a part of the supporting beam 17 of the tank 2.

Below the outlet opening 8 there is a shaft 18 with a gate valve 19. The gate valve 19 is considered to be the most suitable type of valve for this application because it can withstand heavy materials. The shaft 18 leads down to a receiving chamber 20 which in turn leads to a dispensing pump, preferably a screw pump 21. The pumping system will be described in more detail with reference to fig. 5.

As mentioned above, the opening 8 can be closed by means of a gate valve 19. The gate valve has a shutter 22 operated by an actuator 23. The transmission may be a hydraulic cylinder as shown. The gate valve may be opened from a fully closed position to a fully open position corresponding to 100% of the cross-sectional area of the aperture, but intermediate positions are also envisaged in order to control the output of material from the tank.

The output is mainly controlled by adjusting the gate valve opening. The amount of material discharged is determined by the capacity of the pump 21. For this reason, a charging position indicator (not shown) is provided in the receiving chamber 20, which ensures that the gate valve opening can be reduced when the charging position in the receiving chamber reaches a certain height. In order to leave room for the height measurement, the horizontal length of the shaft to the receiving chamber 20 is greater than the horizontal length of the valve 19. At the bottom, the receiving chamber 20 is shaped like a cylinder, in which a feed screw (not shown) is arranged for feeding the cuttings into the pump 21. A cleaning nozzle may be mounted in the receiving chamber (preferably in the upper part) for flushing out residual cuttings after emptying the tank.

Instead of the screw pump 21, other types of displacement pumps may be used, such as a double piston pump. Suitable dual piston pumps currently used to pump cement may be utilized.

Preferably, the screw pump 21 and the output device 12 are operated at a constant speed.

It may be appropriate to operate the feed screws of the pumps 21 separately. As mentioned above, there are preferably two feed screws (not shown); the first screw is located in the receiving chamber (as described above) and the second screw is arranged behind the first screw, i.e. in the actual pump housing 21. The feed capacity of the first screw is slightly greater than the feed capacity of the second screw. This ensures that the entire working volume of the second screw is filled, which reduces the risk that water is carried out of the cuttings and the cuttings are compressed into a concrete-like mass. Pumps of this type are known, but serve other purposes, unlike the present invention. Preferably, the feed screw is directly driven by the hydraulic motor. This provides strength, excessive pressure and torque protection, and a small structural size. The downstream of the pump used is preferably formed by a smooth steel tube (optionally with a transition to the hose) which is acid-resistant, with gentle bends and with as few cross-sectional changes as possible.

Tests have shown that it works well so that the first screw runs at a rotational speed of more than 50% of the second screw. This may be desirable to some extent but results in an increase in viscosity and an increased risk of clogging the end of the receiving chamber. If a separation operation of the first screw is involved, the torque control of the screws will be a parameter.

A device 24 is provided for introducing liquid and/or polymer into the transition between the receiving chamber 20 and the pump housing 21. The addition of a solution containing up to 20% water and 0.5% polymer has proven effective. Injecting soft soap can replace the added polymer mixture. The cuttings are then broken up and made highly viscous, but if the feed is sufficient, the pump can function satisfactorily without the addition of polymer. The discharged material is too viscous to flow, but can still be pumped through a pipeline system without a sharp bend. The resistive torque within the pump can be measured by a sensor to determine whether and how much liquid to inject.

The pump and the pipe are arranged so that it can be used with a smooth bore pipe having the largest possible bend radius. Dimensional variations within the tube and between the tube and the hose should be avoided. It may be sufficient for the pump 21 to have a nominal pressure of 12 bar. The pump may have a guard against dry running and a wear monitor. The internal diameter of the discharge line/hose is suitably between 6 "and 8". The inside of the hose may be coated with a plastic to make it smoother. Preferably, the ship is also equipped with these hoses (e.g. on reels) to avoid using standard discharge hoses that are not smooth enough or have limitations.

Preferably, a pressure gauge is provided within the pump for monitoring the pressure within the pump.

In addition to the addition of water and/or polymer, air may be injected, preferably at one end of the pump, as indicated at 25. The air injected in the form of a blast can break up hard solidified pieces of material. It is also conceivable to use air blowing in the discharge line in order to assist the material to come out downwind.

The output means 10 serve to convey the material towards the output opening 8. The material should be removed by the output device 10 as little as possible to avoid unnecessary agitation. All output arms 15, 16 sweep across the flat base 6. Which carries material through the flat bottom 6 portion and up to the output opening 8. Furthermore, the two arms 16 sweep over the conical edge 5 of the tank 2 in order to facilitate the movement of the material down towards the bottom 6. As mentioned above, the outlet opening 8 extends all the way from the lower edge of the conical rim 5 to the conical portion 11 of the outlet mechanism. This will minimize the movement of the cuttings through the output opening 8. Ideally, the same material should not be pushed along the bottom 6 for more than one revolution.

The description will be explained in more detail with reference to fig. 6 and 7. These two figures show the conical portion 11 with arms 15, 16. The arms 15, 16 and conical portion 11 are connected to a hub (hub)30, which in turn is connected to a drive shaft 31 by splines. The drive shaft 31 is directly driven by a hydraulic motor 32 fixed to a collar 33. The collar 33 depends from an inner cone 34, which inner cone 34 is in turn fixed to the bottom 6 of the tank 2.

Below the bottom 6 of the tank is a cover 35 which seals a space 36, in which space 36 the engine is placed. This space 36 is oil-filled. At the location where the drive shaft passes through the collar 33 is a lip seal 37 which seals the oil filled space 36 at the upper part of the space 36.

The gap 38 (see fig. 7) between the conical portion 11 and the hub 30 on the one hand and the inner cone 34 and the collar 33 on the other hand is filled with air. This is to avoid that material in the can that may penetrate between the conical portion 11 and the inner cone 34, penetrates the lip seal 37 all the way through and cause damage thereto. In order to maintain an airtight seal, a passage 39 is provided in the collar 33 through which air under pressure is delivered to the gap 38.

In the embodiment shown, the engine 32 is mounted from below. However, with a suitably sized introduction opening, it is still easy to install from above.

Above the hub 30 and bolted thereto is a conical tip 40. The conical top 40 serves to lead the material out to the conical portion 11. The connecting section between the conical tip 40 and the hub 30 forms a bolted ring to allow the conical tip to be replaced by a conventional stirring arm if the material being conveyed needs to be stirred during the conveying process.

Fig. 8 shows a hydraulic diagram of a delivery system according to the invention. The tank is schematically indicated 2, the output 10 and the hydraulic motor of the output 10 is indicated 32. The figure also shows the transmission 23 for the valve body 22 and the hydraulic motor 50 for the pump 21. The engine 32 of the output device is controlled by a two-way valve 51 on the discharge side. Here also a throttle 52 ensures a smooth start of the output. A pressure relief valve 53 is also provided adjacent the pump 21. The continuous connection of the motor 50 of the pump 21 to the motor 32 of the output device 10 ensures that the speeds of these motors are always matched. In connection with the engine 50, there are also provided a pressure sensor 54, a torque limiter 55 and a proportional control valve 56.

The actuator 23 of the hydraulically controlled valve body 22 is fitted with a three-way valve 57 and pressure reducing valves 58 and 59, the pressure reducing valves 58 and 59 being in opposite directions. A position sensor 60 is also provided. The transmission 23 can be operated independently of the engines 32 and 50 and is the most important device to control the output from the tank 2.

Fig. 8 also shows a compressed air system with a two-way valve 61 and which is equipped with a pressure sensor 62 and a temperature sensor 63. The system is arranged to blast material into the pump in order to prevent the material from forming a hard mass when low viscosity drill cuttings are present.

A position sensor 64 is also provided which measures the position within the pump inlet chamber and if other parameters allow this will increase the feed rate.

The above describes a pumping device located directly below the tank. However, this is not the most important for material having a vertical path from the tank into the pump. The pump may also be positioned slightly to one side of the tank to allow material to flow into the pump at an angle. By arranging the pump in this way, the flow channels from two or more tanks can lead to the same pump. This allows to reduce the number of pumps and their associated equipment, saving considerable space. This arrangement of the pump is particularly advantageous in the case of low viscosity drill cuttings.

To the rig, the tanks may be used to deliver chemicals, for example, to the rig or vessel. And the output mechanism may optionally be used as a stirrer, possibly together with the stirrer arm described above. It is appropriate to provide EX-protection to all components to allow delivery of flammable chemicals. For this reason, an electric motor is not preferred.

Claims (8)

1. A system for transporting untreated drill cuttings, comprising a tank for containing drill cuttings during transport, the tank having an output means at the bottom of the tank for transporting the drill cuttings out of the tank by pushing the drill cuttings towards an output opening in the bottom of the tank, wherein the tank is arranged below the deck of a ship and comprises a substantially cylindrical upper part and a frustum-conical lower part, which terminates in a substantially flat bottom, the side walls of which extend towards the flat bottom at an angle between 20 ° and 45 ° and which has an inner dome or cone concentrically arranged against the flat bottom, and a displacement pump arranged at a lower level than the bottom of the tank for receiving the drill cuttings and transporting the drill cuttings forward through a discharge line having a substantially constant cross-sectional area and being shaped so as to flow through the same transverse cross-section The flow velocity is substantially the same in cross section near the inner wall of the discharge line, and the flat bottom comprises an outlet opening extending from the side wall of the lower part of the frustum cone towards the inner dome or cone.

2. A system according to claim 1, characterised in that the discharge line is formed of a material having a low coefficient of friction or that the discharge line has an inner wall of such a material.

3. The system according to claim 1, characterized in that the volumetric pump has a first feed screw with a larger feed capacity than a lower second feed screw.

4. The system of claim 1, wherein the dome or cone is formed by a hub in the output device, the hub comprising one or more arms arranged to rotate so as to transport the cuttings towards the output opening.

5. System according to claim 1 or 4, characterised in that the output opening has valves arranged to assume positions between fully closed and fully open in order to control the output speed of the cuttings.

6. System according to claim 1 or 4, characterised in that the tank has a maximum diameter of at least 3 metres and no more than half the internal width available to the vessel, the side wall of the frustum-conical lower part has an angle between 20 ° and 45 °, and the dome or cone has an angle between 20 ° and 45 °.

7. The system of claim 4, wherein at least one arm extends from the hub to a circumference of the flat bottom.

8. The system of claim 7, wherein at least one arm extends at least partially upwardly along the frustoconical lower portion of the canister.