NO20210299A1 - Rigless drilling and wellhead installation - Google Patents

Description

The present invention relates to methods and systems for establishing a well foundation as well as drilling and installation of a surface casing without use of a drilling rig. More specifically it relates to methods for establishing a well foundation subsea using a vessel instead of a drilling rig.

When oil fields are established on the seabed, it is common practice to place a drilling rig at the oil field and do the drilling of wells from this drilling rig. The rigs are stable and provided with equipment to compensate for wind and waves to ensure the well drilling process is performed in a controlled way.

However, drilling with a drilling rig is expensive due to high day rates. It can also be time consuming, as the rig has to be transported to the field and anchored up before drilling can start. Delays may happen due to weather conditions or other unexpected incidents during transport and anchoring of the rig. It is also to some extent overkill to establish a drilling rig for some parts of the operation, especially the first part of the process when the well foundation is established. This initial well establishing process can be drilled in open water without any well control.

After years with large oil fields at acceptable depths and relatively close to land, the focus is now more on smaller fields which also can be more remotely placed as the development in petroleum technology makes is possible and viable to explore these options. At the same time, there is an increase in smaller oil companies trying to enter the petroleum marked by taking over oil fields with presumed marginal income expectations.

The development of smaller fields in more demanding environment also increases the focus on simplification and cost savings. In this context, there is a need to look at the drilling operation, which present a substantial cost even before production has started. This can be an unaffordable obstacle especially for smaller companies or marginal fields.

A further problem that can arise during establishment of a well is release of shallow gas.

It is therefore an object of the present invention to provide methods and systems that will reduce the total cost of a well, thereby enabling exploitation of fields previously regarded as not viable.

Another object of the invention is to provide for a quick escape of an installation vessel in an event of release of shallow gas.

Another object of the invention is to provide a method for establishing well foundation, as well as drilling and installation of a surface casing using a vessel, and thereby without any use of a drilling rig.

Yet another object of the invention is to provide systems for establishing well foundation, as well as for drilling and installation of a surface casing without use of a drilling rig.

According to a first aspect of the present invention, this is achieved with methods using a vessel, and not a rig, for establishing well foundation, and for drilling and installation of a surface casing.

According to a second aspect of the invention, this is achieved with systems using such methods.

The main features of the present invention are given in the independent claims. Additional features of the invention are given in the dependent claims.

A method for establishing a well foundation without use of a drilling rig can comprise the following steps:

• A subsea node, such as e.g. a suction anchor or a subsea template, is installed as a foundation during a rig-less installation and/or drilling operation;

• A bottom hole assembly (BHA) having a drill bit motor and a kelly bushing adapter allows a non-rotating kelly pipe or string to travel freely up and down (i.e. to freely travel axially) and prevents it from rotation; here a kelly pipe is a pipe that is not round in order to prevent rotation. The kelly bushing adapter allows the kelly pipe to freely travel axially, but prevents it from rotation. The kelly bushing adapter can be configured to lock into one from the group consisting of: a suction anchor, a low pressure housing and/or a high pressure housing. As mentioned before, at this stage, the bottom hole assembly (BHA) above the drill motor can move freely axially, but will not rotate.

• The non-rotating kelly pipe or string and the kelly bushing adapter transfer the reactive torque produced from the rotating drill bit to the subsea node (e.g. the suction anchor) and into the seabed.

These and other aspects of the invention are apparent from and will be further elucidated, by way of example(s), with reference to the drawings, wherein:

Fig. 1-5 show a well hole drilling method according to the present invention.

Fig. 6-10 illustrate a casing running and cementing method according to the present invention.

A subsea node 1 is provided for the drilling method. The subsea node 1 forms an outer protective casing for the drilling equipment and will provide a means for anchoring drilling equipment and/or well foundation to the seabed. The subsea node 1 is typically completed with a wellhead assembly comprising an outer well housing or low pressure housing (LPH) 2 and an inner well housing or high pressure housing (not shown). The outer well housing 2 can be provided with an outer conductor piping. The subsea node 1 can be completed with the wellhead assembly prior to or after completion of the well drilling.

The subsea node 1 is preinstalled in a separate operation on a seabed 12. The completion of the subsea node 1 with the low pressure housing (LPH) 2 is often done onshore prior to any other offshore operation while the high pressure housing (not shown) is installed after drilling of the first section of the well.

It is possible to drill the first section of the well without BOP. However, when the well is approaching high pressure subterranean structures, a BOP has to be installed on the subsea node 1.

Drilling at first a part of a well 20 with a vessel 18 and without a BOP, will reduce the cost of each well by limiting the rig time for well drilling and simplify the structure requirement for this first drilling part. Thereafter a rig can arrive and install the BOP directly at a preinstalled wellhead. It is also a safe method as the vessel 18 doesn't need to be straight above the well centre and can easily escape in an event of release of shallow gas.

Fig. 1:

An onshore preassembled drilling assembly according to the present invention comprises a bottom hole assembly (BHA) 5. This BHA 5 can typically comprise a drill bit with stabilizers, a drilling motor, which can be, but is not limited to, for example a drilling motor 6, a kelly bushing adapter 3, a non-rotating or non-circular string or pipe 7, which can be, but is not limited to, for example one piece of a kelly string, a side entry sub 8 with a swivel and a lifting sub 9.

The drilling assembly is lifted into the sea and lowered down on a cable 11 of a vessel crane 19 into the subsea node 1 and the LPH 2. In this context, the cable 11 can be a cable, wire, rope or chain.

The BHA 5 is lowered into the subsea node 1 and the kelly bushing adapter 3 is locked to the subsea node 1. And more particularly, torque keys of the kelly bushing adapter 3 are aligned with the subsea node 1 and then the kelly bushing adapter 3 is locked to the low pressure housing or well housing 2 using a locking mechanism 4. When the kelly bushing adapter 3 is locked to the subsea node 1 and the bottom hole assembly 5,, the bottom hole assembly 5 is prevented from rotational movement or moving sideways, but is allowed to move vertically.

The locking mechanism 4 can be any locking device that can be remotely operated or be configured to be operated by an ROV. The locking mechanism 4 lock the kelly bushing 3 to the subsea node 1 or well housing 2.

Fig. 2A-2B:

While the drilling assembly weight is set down, a fluid is pumped through a hose 10 into the side entry sub 8 down the kelly string 7 in order to drive the drilling motor 6 that spins the drill bit. The fluid can be provided from the vessel 18 or a fluid reservoir on the sea bed. The drill bit of the BHA 5 can be driven hydraulically from a high volume pump (not shown) on the vessel 18 (fig.2A).

A pump 24 for drill cutting removal can be used for the circulation of the fluid. The pump can be positioned on the seabed 12 as shown in fig.2B.

The hose 10 can be, but is not limited to, for example a black eagle hose, a coil tubing or any flexible hosing. The fluid can be any drilling fluid.

The reactional force that is created between the BHA 5 and the seabed 12 under the ground will be absorbed by the kelly bushing adapter 3 and transferred via the LPH 2 to the subsea node 1.

Drill cuttings returns are escaping through cement return ports 23 on the LPH 2 with or without a drill cutting disposal pump system 24

Fig. 3:

Once the total depth is reached, the drilling assembly will be pulled back using the cable 11 of the hoisting mechanism 19 on the vessel 18. The hoisting mechanism can be a crane or winch.

When the drilling motor 6 reaches the kelly bushing adapter 3, or any other catch device if used, the kelly bushing adapter 3 will be unlocked by opening the locking mechanism 4.

Fig. 4:

When the kelly bushing adapter 3 is unsecured, the whole drilling assembly will be pulled up. On fig.4, the kelly bushing adapter 3 is attached to the bottom hole assembly 5. When the locking mechanism 4 is unlocked, the kelly bushing adapter 3 is released from the subsea node 1 or the well housing 2.

However, in another embodiment, the kelly bushing adapter 3 can be part of the subsea node assembly. In this embodiment, the kelly bushing adaper 3 will remain on the seabed when the locking mechanism 4 is unlocked, while the bottom hole assembly is raised to the vessel.

Fig. 5:

The whole drilling assembly is then pulled to the water surface by pulling back on the cable 11 leaving the drilled well hole / borehole 20 ready for running a surface casing assembly.

Fig. 6:

The surface casing assembly is usually prepared onshore into one unit and comprises: a high pressure housing (HPH) 13 and a surface casing 21 with a check valve 22, a HPH running tool 15, a cement stinger 14, a side entry sub 16 with a swivel and a lifting sub 17.

The hose 10 from the vessel 18 is connected to the side entry sub 16.

The whole surface casing assembly is dispatched from the vessel 18 and lowered down on the wire 11 of the vessel crane 19.

Fig. 7A-7B:

The surface casing assembly is stabbed into the LPH 2 and run in the hole 20 on the wire 11. Finally, the HPH 13 latches and locks into the LPH 2.

Under the running-in step, circulation of seawater or other suitable fluid in the well hole 20 can be done using a pump on the vessel 18 (fig.7A), down the hose 10, through the side entry sub 16 and through the HPH running tool 15.

Alternatively, the pump 24 on the seabed can be used for the circulation of the seawater or the suitable fluid through the well hole 20 (fig.7B).

Fig. 8:

The surface casing 21 is cemented in place by pumping cement from the vessel 18, through the hose 10, into the side entry sub 16, through the HPH running tool 15 and down the cement stinger 14.

Cement returns are coming back out through the check valve 22, along outside of the surface casing assembly, and finally the cement returns are flown out through the ports 23 in the LPH 2.

Fig. 9:

The HPH running tool 15 is released and then pulled out of the hole 20 together with the lifting sub 17, the side entry sub 16 and the cement stinger 14 using the vessel crane wire 11.

Fig. 10:

Left on the seabed 12 is a well 20 ready for a floating drilling unit to latch a BOP on to the HPH or wellhead 13.

Finally, the vessel 18 can move to a next well to be made.

It is not compulsory to remove the complete bottom hole assembly 5 from the well 20. In some situations, parts of or the complete bottom hole assembly is sacrificed in the well. In these situations, the cable 11 between the bottom hole assembly 5 and the vessel 18 is cut and the vessel can prepare to drill a new well and/or move to a new location.

In some occasions, a special kelly bushing has to be made if a kelly bushing, that is longer than what the vessel 18 can handle, is needed. Separate pipe sections or lengths can thus be connected together at or on the vessel 18, for example while running all this into the sea. For about a 50 meters hole, potentially a one piece pipe can be used, as mentioned before.

Depending on the length, the surface casing can be deployed as one assembly, if not it can be made up on the vessel 18 and then run into the sea, similar to what is done on a drilling rig.

The weight on the drill bit can be adjusted by a hive compensated crane on the vessel 18. This means that the crane 19 can have some hive compensating equipment thereon.

The total string weight should be configured to give sufficient weight to the bit in order to be able to carry on and/or fulfil the operations.

If the string is not very long, the whole string can be made up onshore and deployed straight from the back deck of the vessel 18 by the crane 19.

If a deeper hole is required, the string can be built of joints in the vessel moon pool. Thus, some handling equipment should be provided by the subsea contractor.

Additional modifications, alterations and adaptations of the present invention will suggest themselves to those skilled in the art without departing from the scope of the invention as defined in the following patent claims.

Claims (6)

C L A I M S

1. Method for installation of a surface casing (21) using a vessel (18) at an oil field, the method comprising:

- preparing a well casing assembly, a high pressure housing running tool (15), a cement stinger (14), a high pressure housing side entry sub (16) and a high pressure housing lifting sub (17) into one unit onshore or on a vessel (18);

- connecting a hose (10) from the vessel (18) to the side entry sub (16) of the surface casing assembly;

- dispatching the well casing assembly from the vessel (18);

- lowering the well casing assembly by means of a crane or winch (19) on the vessel (18);

- stabbing the well casing assembly into the low pressure housing (2) and running it into the borehole (20) supported by the wire (11);

- latching and locking a high pressure housing (13) of the well casing assembly into the low pressure housing (2);

- cementing the surface casing (21) in place by pumping cement from the vessel (18), through the hose (10), into the side entry sub (16), through the high pressure housing running tool (15) and down and out of the cement stinger (14); - releasing the high pressure housing running tool (15); and

- pulling out of the borehole (20) together with the lifting sub (17), the side entry sub (16) and the cement stinger (14) by using the hoisting means on the vessel (18).

2. The method according to claim 1, wherein the well casing assembly is a surface casing assembly comprising the high pressure housing (13) and the surface casing (21) or a conductor assembly comprising a low pressure housing (2) with an outer conductor piping.

3. Method according to claim 1 or 2, wherein cement returns are coming back out through a check valve (22) of the surface casing (21), along outside of the surface casing assembly, and finally the cement returns go out through ports (23) in the low pressure housing (2).

4. System for installation of a surface casing (21) using a vessel (18) at an oil field, the system comprising:

- a surface casing assembly comprising a high pressure housing (13), a surface casing (21), a high pressure housing running tool (15), a cement stinger (14), a high pressure housing side entry sub (16) and a high pressure housing lifting sub (17), where the surface casing assembly is configured to be dispatched from a vessel (18) and then lowered down on a wire (11) of a crane (19) on the vessel (18) and is further configured to be stabbed into a subsea node (1) with a low pressure housing (2) and to be run into a borehole (20) on the wire (11); and

- a hose (10) from the vessel (18) and connected to the side entry sub (16) of the surface casing assembly;

wherein the high pressure housing (13) of the surface casing assembly is configured to be locked into the low pressure housing (2);

wherein the cement stinger (14) is configured to cement the surface casing (21) in place in the borehole (20) by means of a pump configured to pump cement from the vessel (18), through the hose (10), into the side entry sub (16) and through the high pressure housing running tool (15); and

wherein the high pressure housing running tool (15) is configured to be released and pulled out of the borehole (20) together with the lifting sub (17), the side entry sub (16) and the cement stinger (14) by using the wire (11) of the crane (19) on the vessel (18).

5. System according to claim 4, further comprising a check valve (22) of the surface casing (21) and return ports (23) in the low pressure housing (2), wherein cement returns are coming back out through the check valve (22) of the surface casing (21), along outside of the surface casing assembly, and finally the cement returns go out through the return ports (23) in the low pressure housing (2).

6. System according to claim 4 or 5, further comprising a pump (24) configured for removal of drill cuttings.