WO2013055225A1

WO2013055225A1 - System for active sealing of a drill string

Info

Publication number: WO2013055225A1
Application number: PCT/NO2012/000056
Authority: WO
Inventors: Per Espen Edvardsen; Tom Kjetil Askeland
Original assignee: Siem Wis As
Priority date: 2011-10-11
Filing date: 2012-10-04
Publication date: 2013-04-18
Also published as: NO20111380A1; NO334008B1

Abstract

A system is described for an active sealing barrier in connection with drilling in water carrying or hydrocarbon carrying wells, comprising two or more active sealing elements (30a, 30b, 30c) arranged in a housing (20) and with a mutual distance apart that is greater than the length of a pipe coupling (11) which makes it possible to have a leak proof pressure barrier when a drill stem (10) of a varying diameter is inserted into or taken out of a well, and also that the system comprises a number of inlet channels (50a, 50b) for injection/evacuation of a pressure medium, arranged to distribute the pressure load between said sealing elements (30a, 30b, 30c).

Description

SYSTEM FOR ACTIVE SEALING OF A DRILL STRING

The present invention relates to a system for an active sealing barrier in connection with drilling in water carrying or hydrocarbon carrying wells, comprising two or more sealing elements arranged in a housing or container.

In more detail the invention relates to equipment, a system and method for actively sealing around a drill stem that moves into or out of oil wells and gas wells. The invention can be used for all water carrying or

hydrocarbon carrying types of wells including wells that have a valve tree (subsurface safety valves) placed on the ocean bed, a platform, a vessel, an installation and on land .

The invention relates to systems and methods that make intervention and drilling possible in the above mentioned water carrying or hydrocarbon carrying wells and in particular for ocean based wells both with and without using a riser connection to a surface vessel or an

installation. The system and the method cover work in the above mentioned water carrying or hydrocarbon carrying wells carried out with the help of a drill stem. The invention will represent an active seal around a drill stem that moves into or out of water carrying or

hydrocarbon carrying wells. The invention relates to situations where the well pressure is higher and lower than the surrounding pressure at the valve tree, this means that the invention will withstand pressure from both sides during operation and testing. Typical seals for this use can be so-called annulus valves (annular preventers) that are normally found as standard equipment during drilling operations. These valves are normally non-rotating and when in an open position provide the necessary opening for drilling equipment and

completing equipment to go through, normally 18¾" internal diameter. They are normally closed in that a hydraulic function pushes on a rubber element which is thereby forced in towards the equipment that is in the valve, thus to establish a hydraulic seal over the rubber element.

There are also alternative embodiments where the sealing element itself is installed on a bearing, which means that the element rotates with the drill stem. These rotating elements are normally closed in the same way as the stationary elements mentioned above. Today's rotating elements offer a somewhat reduced available inner diameter to be able to drive drilling and completing equipment through, typically 11" inner diameter.

The invention will be particularly suited to operations that involve drilling through existing production pipes in a well, and then particularly ocean based wells where the invention, together with other systems, will be able to contribute to removing the riser connection to the surface vessel or installation.

Today' s methods to carry out well interventions or drilling in ocean bed installed wells with the help of a drill stem are based on using a riser connection between the wellhead and the surface equipment on the surface vessel or the installation. This requires a large, and thereby a costly, surface vessel or surface installation which must have room for blowout preventer (BOP) for the riser, risers for the ocean depth where the work is being carried out and also other equipment which is required for pressure control and emergency handling.

For a long time active seals have been used for so-called "annular preventers (annular BOP)". These have large rubber elements that are forced together with the help of hydraulic pistons. Normally these seals are stationary without rotation, but there are some embodiments where the seal itself rotates inside the casing on a ball bearing.

From patent literature reference is made to, among others, US 2012/0043726 Al that describes a system for a sealing barrier in connection with drilling in hydrocarbon

carrying wells, comprising two or more active sealing elements. US 2012/0043726 Al does not describe that the sealing elements can be actively opened and closed, but on the other hand are adapted to be elastically regulated according to the diameter of the drill stem. Furthermore, there is no description that a friction reducing medium can be injected between the packer elements in the seals.

US 2010/0218937 Al describes a system for a sealing barrier in connection with drilling in hydrocarbon

carrying wells, comprising several sealing elements. US 2010/0218937 Al does not describe that the sealing

elements can be actively opened and closed and are adapted to elastically regulate themselves according to the diameter of the drill stem or that it is known to have inlet channels for a pressure medium between the seals.

Similarly, US 2005/0061499 Al shows a system for a sealing barrier in connection with drilling in hydrocarbon carrying wells. US 2005/0061499 Al does not show that it is known that a friction reducing medium can be injected between the packer elements in the seals, or that it is known to have inlet channels for a pressure medium between the seals.

The present invention has several objects, among them to prevent drilling fluid from the well to be able to leak into the environment, and also to make it possible to be able to supply the well with a pressure in addition to the drilling fluid and thereby be able to carry out pressure controlled drilling operations. The invention will be able to prevent that fluid flows from the surroundings (for operation without a riser: water, and for operation with a riser: drilling fluid) into the well.

With a barrier is meant that the system isolates the well pressure and that one continuously monitors the state of the barrier with the help of pressure and temperature monitoring above, between and below the seals. The seals are assembled so that they form a common outer pressure container that shall retain the pressure.

According to the invention a system is provided for an active seal barrier in connection with drilling in water carrying or hydrocarbon carrying wells, comprising two or more sealing elements arranged in a housing or container and with a mutual spacing apart that is greater than the length of a pipe coupling and which makes possible a leak proof pressure barrier when a drill stem with a varying diameter is led into, or taken out of, the well and also that the system comprises a number of inlet channels for injection/evacuation of a pressure medium arranged to distribute the pressure load between said sealing

elements .

Alternative embodiments are given in the dependent claims The active sealing barrier can be arranged to provide a full opening for drilling tools when it is not in use and the sealing barrier can, when activated, be arranged to provide a seal against a drill stem of a varying diameter.

One or more seals can be arranged to be actively opened and closed when the drill stem coupling shall be led through the system. The individual active sealing element can be connected to a hydraulic line arranged to inject grease or a friction reducing medium directly into the sealing surface between packers in the sealing elements and the drill stem to lower the friction and temperature and also to increase the sealing effect against gas.

Furthermore, the pressure difference between the well and the surroundings can be arranged to be distributed with an equal part to each of the seals that are active at any given time via a pressure distribution system that communicates with the hydraulic fluid between the seals through the hydraulic gates.

The sealing elements can comprise at least one disc-formed or ring-formed packer element of an elastic material, such as an elastomeric material, arranged to surround said drill stem. Furthermore, the sealing elements can be arranged to rotate inside the housing. With well safety equipment is meant the required blowout safety appliances (BOP, stop valves, etc.) and the necessary connections for guiding and control of well fluid or drilling fluid. Belonging to the invention is a pressure distribution function, a so-called gradient system. The system is connected into the spaces between the sealing elements via hydraulic pipes and has several functions. One function is to generate a given pressure in the space between two seals, in this way to control the pressure load to the individual seal and thereby distribute the total load over two or more seals. Another function is to represent an evacuation/supply of fluid in the space between two seals when the pipe connection enters into this space with its larger diameter. With the help of the gradient system the total pressure load between the annular space of the well and the surroundings is distributed over the seals that are active at any given time.

Example: If there is a total pressure load of 90 bar over the seals, the pressure will be distributed with a 30 bar part-pressure over each sealing element. Thus, the load on the individual seal is reduced, the life span is increased significantly and one has a redundance function if a seal should have a reduced effect.

The seals can be actively regulated so that during

drilling operations it is possible to be able to lead pipe couplings through and also to be able to function as a leak proof barrier when the drill stem is led through the system. The sealing elements can be placed mutually spaced apart with a distance that means that only one of the sealing elements will be able to be exposed to a pipe coupling in the drill stem at any given time. The drill stem is driven into the well with the help of the weight of the drill stem and downhole tools, and also any forces that are supplied with the help of external systems. In connection with drilling operations in wells with the help of a drill stem, snubbing or coil pipes, the necessary complimentary systems will be used to maintain other functions that are required for the carrying out of the operation (cutting and sealing functions, disconnection systems, drilling fluid systems, etc.)- This invention encompasses the active sealing function where two or more seals are combined, the distribution of the pressure load over these, and also injection of a

lubricating agent directly into the sealing surface. The invention does not take into consideration how the drill stem that shall go into the well is operated or driven and thus covers any form of such methods.

Furthermore, the sealing elements can comprise at least one disc-formed or ring-formed packer element of an elastic material, such as an elastomeric material,

arranged to surround said drill stem. The sealing elements can also be arranged to rotate in the housing or the container .

The invention shall now be explained in more detail with reference to the enclosed figures, in which:

Figure 1 shows a section of the system according to the present invention.

Figures 2-8 show the system in different

configurations, as a drill stem is driven through.

Figure 9 shows a known sealing arrangement that can be integrated with the present invention.

Figure 1 shows a possible embodiment of the invention. An outer container or housing 20 is assembled by three active sealing elements 30a, 30b, 30c. Through this runs a drill stem 10 which, at regular intervals, is connected together via a pipe coupling 11. The system is, in this case, mounted on the top of another required well safety device 40. In the spaces between the sealing elements 30a, 30b, 30c, there are hydraulic pipe couplings 50a, 50b for communication with a pressure distribution function. In addition, the hydraulic pipe couplings 50a, 50b make it possible to move fluid according to need, typically when the pipe coupling 11 with its increased diameter compared with the rest of the drill stem 10, enters, or comes out of, the areas between two closed seals. To reduce

friction, supply cooling and also prevent leaks, any individual sealing element 30a, 30b, 30c can be supplied with grease or other friction reducing agents directly into the sealing surface between the sealing element and the drill stem 10 via the inlet channels 60a, 60b, 60c. For the opening and the closing of the sealing elements 30a, 30b, 30c hydraulic pistons can be used, for example, that force the sealing elements together. Other known techniques can also be used. Grease or another friction reducing agent will be injected with a pressure which is preferably somewhat higher than the highest pressure that surrounds the seal from the well or the surroundings and will, in that way, ensure that inflow of fluid or gas through the seal will not happen.

The seals can be controlled from an open, normally 18¾" ID, to close against a drill stem. The embodiment can be with a rotating seal (the seal is fastened to a bearing) or with a stationary seal without a bearing.

Figure 1 shows an embodiment of the present system

comprising three sealing elements 30a, 30b, 30c that are all open. The sealing elements are placed a mutual distance apart which makes room for a pipe coupling 11 between them. The configuration and the system can be used independently of whether the well safety system 40 is localised on the ocean bed or is available at the

surface/land. Other equipment that is required in the operation can be installed below and/or above the sealing system. Figure 2 shows the system in operation with all the sealing elements 30a, 30b, 30c closed against the drill stem 10. In this situation the total pressure load will be distributed over the three elements 30a, 30b, 30c.

Figure 3 follows the situation in figure 2 and shows a situation where the lowest sealing elements 30b, 30c seal against the drill stem 10 while the uppermost 30a is opened sufficiently to let the pipe coupling 11 pass with minimal wear. The pressure is now held, in the main, by the middle 30b and the lowest sealing element 30c.

Figure 4 follows the situation in figure 3 one has now closed all the three sealing elements 30a, 30b, 30c against the drill stem 10, and the pipe coupling 11 is between the uppermost 30a and the middle element 30b.

Figure 5 follows figure 4 and the middle sealing element 30b is now opened sufficiently to let the pipe coupling 11 pass with minimal wear down to be in position immediately above the bottom element 30c. The pressure is now held, in the main, by the top 30a and the bottom 30c seal elements.

Figure 6 follows figure 5, one has now closed all the three sealing elements 30a, 30b, 30c against the drill stem 10, and the pipe coupling 11 is between the middle element 30b and the bottom element 30c.

Figure 7 follows figure 6, one has now opened the lowest element 30c sufficiently to let the pipe coupling pass with minimal wear. The pressure is now held, in the main, by the top 30a and the middle sealing element 30b.

Figure 8 follows figure 7, one has now closed all the three sealing elements 30a, 30b, 30c against the drill stem 10, and the pipe coupling 11 is now below all the elements 30a, 30b, 30c and further operation of the drill stem 10 can be initiated. The pressure load is now

distributed over all the closed elements. Figures 2-8 show how the active seals 30a, 30b, 30c is normally operated when a pipe coupling 11 shall be driven through to ensure that the sealing elements 30a, 30b, 30c are not subjected to wear from the pipe coupling 11 which one normally experiences after operations on the drilling deck. The sequence is carried out in reverse order if one pulls the drill stem out of the well.

In the following, different embodiments shall be

described, but it must be understood that other

configurations are also possible within the framework of the invention.

Configuration 1; embodiment of the present system

localised on the top of an imagined configuration in connection with a drilling operation.

The system refers to figure 1. The system can be comprised of a well safety system 40 for use when drilling and the active seal 20 including the sealing elements 30a, 30b, 30c. The active seal 20 is placed above the well safety system 40 in the assembly and will maintain pressure control during drilling or intervention work. The seal 20 shall be able to withstand pressure from both sides, but preferably higher pressure from the well side than from the surroundings. Above the active seal 20 there is initially no other equipment. This means that during operation where the well safety system 40 and the active seal 20 are placed on the ocean bed they will be

surrounded by water. The drilling intervention or well intervention will then be carried out without a riser. Configuration 2; embodiment of the present invention localised on the top of an imagined configuration in connection with a drilling operation. The system refers to figure 1. The system is comprised of a well safety system 40 for use in drilling and the active seal 20 includes the sealing elements 30a, 30b, 30c. The active seal is placed above the well safety system 40 in the assembly and will maintain pressure control during drilling or intervention work. The seal shall be able to withstand pressure from both sides, but preferably higher pressure from the well side than from the surroundings.

A riser 70 is connected above the active seal 20 that leads the drill stem 10 and other well tools into and out of the well, in addition to being able to handle the drilling fluid. The riser 70 can run in both water and air to be able to lead associated equipment on board an installation, a floating rig or on land.

The present invention can be combined with a sealing arrangement for dynamic sealing around a drill stem, as described in US 2010/0218937 Al . This sealing arrangement for dynamic sealing around a drill stem 10 or a coiled pipe, can comprise an extended, dynamic sealing unit 110 which is arranged to surround the drill stem, as the sealing unit 110 comprises a number of sets of main seals 120, arranged mutually spaced apart in the longitudinal direction of the sealing unit 110, where said main seals 120 comprise at least one disc-formed or ring-formed packer element 130 of an elastic material, such as an elastomeric material, arranged to surround said drill stem. Furthermore, said main seal 120 can comprise at least one inlet channel arranged to receive a friction reducing medium through, or via the seal, directly into the sealing surface of the packer element 130 against the drill stem.

Thus, the packer elements 130 can make up the packers the sealing elements 30a, 30b, 30c in the present

inventio .

The friction reducing medium can be injected between said disc-formed or ring-formed packer elements 130 via injection lines 140. Correspondingly, the injection lines 140 can be connected to the inlet channels 60a, 60b, 60c.

Furthermore, the sealing unit can be connected to an injector arranged to inject said friction reducing medium via a port 150 in the side wall of the sealing unit, and said friction reducing medium can be oil, grease or similar lubricating agents.

Claims

C L A I M S

1. System for active sealing barrier in connection with drilling in water carrying or hydrocarbon carrying wells, comprising two or more active sealing elements (30a, 30b, 30c) arranged in a housing (20) and with a mutual space apart that is greater than the length of a pipe coupling (11) and which makes it possible to have a leak proof pressure barrier when a drill stem (10) with a varying diameter is inserted into or taken out of a well, and also that the system comprises a number of inlet channels (50a, 50b) for injection/evacuation of a pressure medium, arranged to distribute the pressure load between said sealing elements (30a, 30b, 30c) .

2. System according to claim 1,

c h a r a c t e r i s e d i n that the active sealing barrier is arranged to provide a full opening for drilling tools when it is not in use and that the sealing barrier is arranged to provide a seal against a drill stem of a varying diameter when it is activated.

3. System according to claim 1,

c h a r a c t e r i s e d i n that one or more seals are arranged to be actively opened and closed when the drill stem coupling shall go through the system.

4. System according to claim 1,

c h a r a c t e r i s e d i n that the individual, active sealing element (30a, 30b, 30c) is connected to a hydraulic line (60a, 60b, 60c) arranged to inject grease or a friction reducing medium directly into the sealing surface between packers in the sealing elements (30a, 30b, 30c) and drill stem (10) to reduce the friction and temperature and also to increase the sealing effect against gas.

5. System according to claim 1,

c h a r a c t e r i s e d i n that the pressure

difference between the well and the surroundings is arranged to be distributed with an equal part across each of the, at any time, active seals (30a, 30b, 30c) via a pressure distribution system that communicates with the hydraulic fluid between the seals (30a, 30b, 30c) through the hydraulic ports (50a, 50b) .

6. System according to claim 1,

c h a r a c t e r i s e d i n that the sealing elements comprise at least one disc-formed or ring-formed packer element of an elastic material, such as an elastomeric material, arranged to surround said drill stem.

7. System according to claim 1,

c h a r a c t e r i s e d i n that the sealing elements (30a, 30b, 30c) are arranged to rotate in the housing (20) .