Technical Field

The invention relates to a pipe section for use in a multilateral well, and a method for installing a string of pipe into a multilateral well.

Background Art

In the completion and production industry for natural resources, the formation of boreholes for the purpose of production or injection of fluid is common. The boreholes are used for exploration or extraction of natural resources such as hydrocarbons, oil, gas, water and alternatively for CO2 sequestration.

Multilateral (ML) wells have become more common well construction method in oil and gas production.

Multilateral boreholes allow for greater return on investment associated with drilling and completing simply because more discrete areas/volumes of a subterranean hydrocarbon deposit(s) is/are reachable through a single well.

Multilaterals generally require junctions at intersection points where lateral boreholes meet a primary borehole. Junctions are Y-type constructions utilized to create flow paths at borehole intersections and are generally referred to as having a primary or main leg and a lateral leg.

In 1997, the consortium - Technology Advancement of Multilateral (TAML) was initiated.

This group standardized how to describe the functionality of a multilateral junction by defining TAML levels from 1 to 6. Level 1 being the simplest and level 6 the most advanced ML junction.

ML junction level 5 and level 6 defines a level of ML technology where pressure outside the junction is isolated from pressure inside of the junction by the junction equipment. A ML junction with sealing capability is needed for subsea wells when the ML technology is used in a well with downhole flow control of multiple formation zones or when it is needed to prevent ingress of fluids or formation sand at the ML junction.

There is a differentiation between TAML level 5 and level 6. With level 5, it is the pipe and seals installed inside the junction that provides the junction seal. With level 6, it is the junction itself that provides the junction seal. The TAML level 5 technology is the more common used best option as of now. An exit hole (a window) is cut (milled) in the casing of the main wellbore. The lateral wellbore is drilled out from the window. The ML junction is a guide installed inside the casing and across the window of the main wellbore. The ML junction is used to guide the pipe into below the window in the main wellbore or out and into the lateral.

US 2004/0035581 Al disclose how to make a level 5 system by aligning ports in the completion with the junction window.

It is the internal pipes that provide pressure isolation from outside the junction. It is costly to install the pipe and seals inside the junction and the reduced final internal diameter at the junction is restricting use of the wellbore.

Level 6 prior art: The prior art of ML technology at level 6 is to manufacture the junction on surface as one piece of steel. The junction is then installed at the end of a casing string in an enlarge borehole. Two boreholes with different destination are then drilled out from below the junction. The value is limited due to cost and complexity of constructing the host wellbore to a size that allows the junction to be deployed at desired depth.

To reduce the size of the large host wellbore and to deploy the junction deeper, there is also prior art on collapsing one leg of the junction, so it is deployed in a smaller size. This is known from US9303490. The junction is restored to original shape once placed downhole. However, this has proven less successful as the junction may damage from being collapsed or from being reworked into original shape.

Another version of same idea is thought in US 5875847. The junction (or segment of casing) is prepared on surface with a primary and secondary bore. The secondary bore is temporary blocked with a removeable plug and installed in the wellbore at the predetermined location. The removable plug is drilled out when drilling the lateral.

US 2018/0274333 Al. The idea is to manufacture the junction at surface but to the installation into a well in two parts. He discloses a pipe section with a premanufactured window. The window in the pipe section is closed off with an inner pipe of low melting metal sleeve. The low melting sleeve is here performing the same function as the removal plug in US 5875847. The sleeve is removed with a heat source and the lateral is drilled. A prefabricated junction is installed at the window. Because both the window and junction are manufactured at surface, the fit can be precise. The inventor cannot or does not consider the idea that a precise fit can created a sealing junction. Most of the discussion and all claims are around melting metal downhole so that it can later solidify and created a seal at the junction. There is some language that implies a fit so good that it contains pressure, but this statement includes reference to 'lining of the first part' which is of melting metal, 'a second part 650 adapted to mate with the first part and connect with the first part through the lining of the first part to form a pressure seal connection between the first part and the second part, the first part has a larger diameter than the second part, the second part is adapted to be mated through the port from the inside of the first part towards a lateral borehole after the first part has been installed in the well'.

The idea creating a junction downhole by mating to pipe sections is also discussed in US 6 012 526 A. The main idea is cut a precise window downhole, '...provides a precise window shape making sealing thereagainst more attainable'. Several methods of how to create a seal at the junction are discussed. A monitoring and telemetry method is disclosed to oversee and control the cutting of the window from surface.

US 2021/0222548 Al disclose how to bring electric power and communication signals in across a conventional multilateral system made from magnetic steel. Many of these methods become redundant when a junction is made from nonmagnetic composite material.

None of the prior art discloses a multilateral junction that is easy to install in the downhole to extend the pipe section to several additional boreholes in the well or takes advantage of modern materials to obtain seal at the junction.

The prior art disclosures also fail to disclose a multilateral pipe section and a method for installing the pipe section in a well construction that does not requires any different drilling process than regular drilling process for single bore wells.

Other advantaged and special features of the present subject invention will be made clear in the following detailed description, the attached drawings, and the following patent claims.

Summary of the invention.

The invention relates to a multilateral pipe section for use in a multilateral well construction, comprising a substantially cylindrical shaped first part having a lining surrounding a port in the first part, the lining being arranged flush with the circumference of the first part, a second part is adapted to mate with the first part and connect with the first part through the lining of the first part to form a connection being a pressure seal between the first part and second part, the first part has a larger diameter than the second part, the second part is adapted to be mated through the port from the inside of the first part inside of the first part towards a lateral borehole after the first part has been installed in the well. A sealing connection is formed intrinsically when the two parts joins, without need for additional sealing material or additional operational steps.

Preferably, the lining and at least the part of the external surface of the second part adapted to connect with the first part, are made of a material that has low friction and is adapted to form a seal between the connection between the first part and second part.

Preferably, at least a part of the multilateral pipe section is made from a composite material, such as thermoplastic

Preferably, the lining has an inclined surface from the inside surface of the first part to the outside surface of the first part

Preferably, wherein the first part has an elliptical shaped port built into the side wall of the first part.

Preferably, the elliptical port is formed so that the second part is adapted to exit through the elliptical port from the inside of the first part and form a pressure seal around the port.

Preferably, the multilateral pipe section is equipped with a resistivity imaging tool on the outer surface of the first part, the resistivity imaging tool is adapted to position the first part in alignment with a lateral borehole.

Preferably, the resistivity imaging tool is adapted to use electromagnetic wave reflection processing.

The invention also relates to a method for installing a pipe string into a multilateral offshore well construction, comprising a multilateral pipe section according to the invention, wherein the method comprises the steps of a) installing a pipe string including the first part of the multilateral pipe section into a drilled main bore, b) positioning the port of the first part in alignment with a drilled lateral bore of the drilled main bore, c) guiding the second part of the multilateral pipe section through a port from inside the first part positioned in the main bore and towards the lateral borehole, d) locking the first part and the second part together into a sealable connection

Preferably, the method comprising a repetition of the steps a-d) for a second lateral borehole.

Brief description of drawings

Figure 1 shows an example of a pipe string according to the invention.

Figure 2 shows the first part of the multilateral pipe section or junction with front external view of the port

Figure 3 shows the first part of the multilateral pipe section of junction in a side- viewed cut away (cross-sectional view)

Figure 4 shows the first part of the multilateral pipe section or junction in a side- viewed cut away (cross-sectional view with the second part installed).

Figure 5 shows the first part of the multilateral pipe section or junction in a superimposed transparent front and back view so the full circumference of the port in the pipe wall can be seen.

Figure 6 -14 shows an example of the well construction utilizing a pipe string including the multilateral pipe section according to the invention.

Detailed description of the invention

Figure 1 shows a possible embodiment of a pipe string 1 with at least one multilateral pipe section 6a, 6b according to the invention.

The pipe string 1 comprises several pipe sections 4, a conventional downhole safety valve 3, control line 9 and electrical line 10 and a packer 5.

In addition, the pipe string 1 shown in figure 1 has two multilateral pipe sections 6a, 6b. The number of pipe sections 4 and multilateral pipe sections 6a, 6b may vary depending on the length of a main borehole and the number of lateral boreholes associated to the main borehole.

The pipe string 1 may be suspended from a conventional tubing hanger 2 arranged at the well head as illustrated in the figure 1.

The multilateral pipe section or junction 6a, 6b is made of a composite material. It may for instance be a composite material or other material that have a degree of flexibility to enable the connection of parts of the multilateral pipe section 6a, 6b. The other components of the pipe string may also be made of a composite material, but the invention is not limited to this.

Figure 2 - 5 shows the assembly of a multilateral pipe section of junction 6 according to the invention. For simplicity we use the reference number 6 as reference number instead of 6a, 6b when we refer to the figure 2-5. The features 6, 6a, 6b are equal.

Figure 2 shows a first part 7 of the multilateral junction 6. The first part is substantially cylindrical shaped. The first part 7 has a port 13. The port 13 has been prefabricated into the first part. The port 13 is arranged as a through hole 13 in the sidewall of the first part 7 as shown in the figure. Preferably, the port 13 has an elliptical shape. The elliptical shape is oriented in a way so that the longest diameter is extending along the longitudinal length of the first part 7.

The first part 7 has further a lining 14 forming an edge to the port 13 in the first part 7. The port 13 is formed as a through hole at a longitudinal side of the first part 7 as shown in the figures 2-5

The first part 7 may further have an imaging tool 12. This imaging tool 12 is arranged on the outside of the first part 6. The imaging tool 12 provides an easier positioning of the first part 7 so that it is correctly aligned with the entrance of a drilled lateral borehole.

Figure 3 shows a cross section of the first part 7, viewed from the side. From the figure, it is illustrated that an lining 14 defining the port 13 in the first part 13 is inclined. This is illustrated by the reference numbers 14a and 14b.

From the figures it is further shown that the inclined lining 14 (figure 6) has the same inclination towards the same direction.

As shown in the figure, this means that the thickness of the material or the first part 7 is continuously decreasing at a part of the lining 14 defined with reference number 14a. At the opposite side of the lining 14 defined as reference number 14b the thickness is continuously increasing

Figure 4 shows the assembled multilateral pipe section or junction 6. The figure shows a second part 8 that is adapted to be inserted through the port 13 in the first part 7 and installed into the lateral wellbore 21 (figure 8). The second part is substantially cylindrically shaped. The diameter of the second part 8 is smaller than the first part 7 to be able to be inserted at the inside of the first part 7. The port 13 must thus be designed so that the second part 8 can exit through the port 13 and form a pressure seal around the port 13. This is done by shaping the port 13 with the inclined lining 14a, 14b. The inclination is equal to the angle or inclination that the lateral bore is drilled about from the main bore. This ensures that the second part 8 aligns with the shape of the port in the first part 7.

In addition, the materials with low friction and sealing ability is used in the lining 14 of the port 13 in the first part 6 and on the external surface 23 of the second part 7. Possible material may be a be a wide range of thermoset plastics. Heavy density polyethylene (HDE), the polyvinylchloride (PCV) family of materials and polyetheretherketone (PEEK) are mentioned as examples.

The final position of the second part 8, the outer diameter of the second part 8 is locked in place and seals against the port 13 of the first part 7 as shown in figure 4. The main portion of the second part 8 is in this final position extending inclined from the first part 7 and further into the lateral wellbore.

As the lining 14 of the port 13 of the first part 7 and the external surface 23 of the second part 8 are made of a material that has some degree of flexibility, the part 7 and 8 may be forced into connection without further attachment means. The parts

7 and 8 may thus be snapped into place in the connection. As shown in the figures it is more specifically the end portion of the second part 8 that is connected to the lining of the first part 7.

The inclination of the lining 13 in the first part also facilitates the connection. There are flanges 24a, 24b at the inside and outside of the second part 8, that facilitate the connection between the first and second part 7, 8 after the second part 8 has been forced into place in the port 13.

Figure 5 shows a superimposed transparent front and back view so the full circumference of the port 13 in the pipe wall can be seen. The reference number 14 refers to the lining which is inclined as shown in figure 3.

The invention disclosed is a multilateral pipe section that is built and installed in two parts. The first part 7 is a pipe section with the prefabricated port 13. The part

8 is a pipe section that can be inserted through the port in the first part 7 and installed into the lateral wellbore. In its final positions, the outer diameter of part 7 will lock in place and seals against the end port of the second part 8. The process repeats so there is no limitation to the number of laterals. The result is a TAML level 6 functionality and the junction with the first part 7 and second part 8 provides mechanical and pressure integrity against the formation into where it is installed.

Figure 6-14 shows an example of a well construction that utilizes the multilateral pipe section or junction 6 according to the invention.

Figure 6 shows an overview of an open hole horizontal well 20 that is drilled to a target depth. The open hole horizontal well 20 is arranged below a cased hole section, similar to the cased hole section as shown in figure 1.

In addition to the main wellbore, there may be drilled a few lateral wellbores, such as the wellbores illustrated in figure 8 to 11. Figure 7 shows the installation of a pipe section or sand screen 30 at the innermost depth or lower interval of the open main wellbore 20. The pipe section or sand screen 30 may be secured to the bore hole through an open hole packer 30a.

Figure 8 shows a first lateral wellbore 21 that is drilled from the main wellbore 20 that has already been drilled. As illustrated in the figure, the drilling of the new hole starts above the pipe section or sands screen 30 that has been introduced into the well.

Figure 9 shows installing the first part 7b of the multilateral pipe section of junction according to the invention, into the well. The port 13 (figure 2) of the pipe section is arranged so that it matches the newly drilled first lateral bore hole section 21. The resistivity imaging tool 12 (figure 2) that is arranged on the outside of the multilateral pipe section or junction 6b aid in the placing the port 13 adjacent to the entrance of the drilled first lateral bore hole 21. The bottom end 7' of the first part 7b enters and connect with the top 30' of the pipe section 30 that is already arranged in the main wellbore 20. The first part 7b is then secured to the bore hole 20 with through an open hole packer 31. The imaging tool 12 may provide real time imaging data transmission of the image to the surface. Real time imaging data transmission may also be used to assist in the guiding of the second part 8b through the port 13.

Figure 10 shows the multilateral pipe section of junction 6a installed in the well 20, 21. The second part 8b of the multilateral pipe section or junction 6b is inserted into the first part 7b. The second part 8b comes into final position when the bottom 8' is extending into the drilled first lateral bore hole 21. The opposite end of the second part 8" is mated with the first part 7b. The second part 8b thus seals in the port 13 of first part 7b.

The process of figure 8-10 is repeated to include a further drilled lateral bore hole 22 with further multilateral pipe section of junction 6a. This is illustrated in figure 11-13.

The drilling of a new lateral bore hole 22 start above the multilateral pipe section or junction 6b that has already been installed in well.

The process may be repeated until there is arranged a multilateral pipe section or junction 6 in each drilled lateral borehole 21, 22. There is no limitation to the number of lateral boreholes in the well.

Figure 14 shows the pipe string 1 for the multilateral well in the horizontal part of the wellbore.

Reference 45 indicates the formation outside of the well and the reference numbers 40 indicates how multiple hydraulic activated well stimulation devices such as FISHBONES (trademark) deployed in multiple laterals can be simultaneously activated with pumping from surface. The simultaneous activation made possible by the sealing multilateral junction.

In addition, there are illustrated optional valves 41 in the pipe string.

The method for installing a string in a multilateral wellbore is performed by the steps defined below:

1. First drill the main wellbore 20 and install the pipe 30.

2. Drill the lateral wellbore 21.

3. Install a string of pipe that include the first part 7b into the main wellbore 20. Position the string of pipe so that the prefabricated port 13 is aligned with the entrance of a drilled lateral wellbore 21.

4. Install a string of pipe that include the second part 8b into the lateral wellbore. Let the second part 8b lock and seal in place with the first part 7b finalize TAML level 6 junction number one 6b.

5. The process repeats, a. drill a new lateral wellbore 22 from the open hole main wellbore 20 at a point above the pipe section 6b. b. Install a string of pipe that include the first part 6a into the main wellbore 20. Position the string of pipe so that the prefabricated port 13 is aligned with the entrance of the new drilled lateral borehole. c. Install a string of pipe that include the second part 8a into the new lateral wellbore 22. Let the second part 8a lock and seal in place with the first part 7a to finalize TAML level 6 junction number two (6a).

The technologies that make this type of level 6 ML junction possible are:

1. The dispensable imaging tool 12, built on the outside of first part 7, that aids in positioning the first part, so that the prefabricated port 13 is aligned with entrance of a drilled lateral wellbore 21.

2. A method of real time image data transmission of the image to the surface.

3. A method of real time position data transmission to the surface to aid in getting the second part 7 out through the prefabricated port 13.

4. Advanced materials in the interphase of first and second part 7, 8 so that a high-quality seal is obtained.

Example of well construction utilizing the invention a) Below a cased hole section, an open hole horizontal well is drilled to target depth. b) The lower interval of the hole section can be preserved with pipe or sand screen that is left in well and secured to the bore hole with an open hole packer. c) A lateral section 21 is drilled from the open hole section 20 already drilled. The drilling of new hole starts above the pipe section already left in the well. d) A section with the first part 7b is installed in the well. The port 13 will be positioned across the newly drilled lateral wellbore 21. The resistivity imaging tool 12 built onto the outside of the first part 7b around the port 13 aids in the placing the port 13 adjacent to the entrance of the drilled lateral wellbore 21. The bottom of the first part 7b enters and connect with the top of pipe section 30 already left in the well 30. The top of the first part 7b is secured to the bore hole 20 with an open hole packer 31. e) A section with the first part 8b is installed in the well. The second part 8b comes to a final position when the bottom is into the newly drilled lateral bore bole 21 and top of first part 8b mates and seals in the port 13 of the first part 7b. f) The process repeats when a new lateral section 22 is drilled from the open hole section already drilled. The drilling of new hole lateral starts above the pipe section 6b already left in the well.

Reference list

1 - an example of a pipe string according to the invention

2 - tubing hanger

3 - downhole safety valve with control line and electrical cable

4 - pipe string

5 - packer

6 (6a, 6b) - multilateral pipe section

7 (7a, 7b) - first part of multilateral pipe section or junction

7' - end of first part of multilateral pipe section

8 (8a, 8b) - second part of multilateral pipe section or junction

8', 8" - opposite ends of the second part

9 - electrical cable

10 - control line 11 - multijunction connection between first part and second part of multilateral junction

12 - imaging tool

13 - prefabricated port 14a, b - edge towards first port

20 - open hole horizontal well

21 - first drilled lateral borehole

22 - second drilled lateral borehole

23 - external surface of second part 40 - Flow activated well stimulation tools, such as FISHBONES

41 - valve

45 - formation outside the well

50 - part of the pipe string with multilateral pipe sections