GB2541030A

GB2541030A - Conductor float valve

Info

Publication number: GB2541030A
Application number: GB1514028.8A
Authority: GB
Inventors: Anderson Neil
Original assignee: Archer Oiltools AS
Current assignee: Archer Oiltools AS
Priority date: 2015-08-07
Filing date: 2015-08-07
Publication date: 2017-02-08
Also published as: GB201514028D0

Abstract

A method of spudding a well 1c comprising, hanging a conductor casing from the drilling deck to the seafloor, lowering the spudding drill string through the conductor and spudding the well for the conductor diameter, and retrieving the drill string. Inserting a float shoe with check valves 94 for cementing through openings near the lower end of the conductor casing, said float shoe having ports aligned with the openings and isolated by packers or swabs 92. Lowering the conductor pipe into the well. Connecting a cementing pipe string to the float shoe, pumping cement through the float shoe and into the conductor casing annulus, retrieving the cementing pipe string and letting the cement harden. Drilling out said float shoe cementing tool and continuing the drilling operation. The float shoe may be aligned with the conductor casing by the use of dogs and grooves 93.

Description

Subsea Well Drilling Method

The present invention relates to a subsea well drilling method and a float shoe. A subsea petroleum well is usually designed with a conductor casing pipe extending from the seafloor and extending for about 100 - 200 metres into the ground. The purpose of the conductor casing pipe is to stabilize the top portion of the drilled ground. The conductor annulus is cemented.

The spudding well for the conductor is drilled without a riser pipe and thus a bare drill string extends through the drilling deck and lower decks without protection. A so-called conductor, or a conductor casing pipe, is the very first casing pipe inserted into a petroleum well during the first stage of constructing the well. The conductor casing pipe is usually assembled from pipe sections having a rather huge diameter, normally 28" (71 cm) or more, and its role is to stabilize the ground before further drilling and insertion of the first "real" casing pipe. A problem of the prior art as shown in Fig. 0 is that during conductor borehole drilling the heavy drill string 3s runs open. There is no riser pipe arranged for the conductor borehole drilling. Vibrations induced on the laterally unsupported but rotationally top driven drill string may be significant and harmful to a) the drill string itself, b) personnel on the decks (21,22, 23), and equipment on said decks.

When spudding the wells in the background art, personnel working on the lower intermediate decks may be subject to exposure to drill pipe rotating in an open environment.

Another problem arises with so-called U-tubing of the cement after injection-cementing the conductor in the conductor borehole, and before the cement sets and hardens. Thus pressure must be held until the cement sets.

Background art

The applicant provides a so-called C-flex casing section with a cementing sleeve valve manipulated by a drill pipe string-borne cementing tool. The cementing tool engages dogs in a ring groove in the valve sleeve to open cementing ports in the cementing sleeve, and injects cement to the casing annulus. A method for inserting casing strings down into a borehole involves a so-called float shoe arranged at the lower end of the casing so as for partly controlling the floatability of the casing string in the well fluid. This is often used for subhorizontal sections of a well.

Figure captions

Fig. 0 illustrates prior art wherein a well template is arranged on the seafloor and a conductor drill bit (7') on a conductor or "spudding" drill pipe string (3s) is about to drill a borehole (1c) in the upper parts of the seabeds below the seafloor (sf). A conductor pipe shall later be lowered and installed and cemented in the conductor borehole (1c). The conductor is for stabilizing the ground during the subsequent drilling for installing the first casing in the borehole, the first casing for extending to the wellhead which may be arranged on the seafloor or on the lower deck (23), on the first casing.

Fig. 1 illustrates having assembled and lowered the conductor casing string (41) from near the drilling string and down to or near a well template.

Fig. 2 illustrates the first drilling step: A drill string is lowered through the conductor pipe and the well is spudded.

Fig. 3a shows the conductor borehole formed to the required conductor depth with the conductor still hanging through the sea from the hang-off device (26).

Fig. 3b shows the drill string tripped out of the conductor pipe, and the conductor pipe having received the conductor float shoe (9) in its lower end (411).

Fig. 3c shows the hangoff device (26) having released the upper end (412) of the conductor pipe (41) and the conductor pipe having been lowered into its place in the conductor borehole.

Fig. 3d shows connecting a cementing string such as a drill pipe string to the float shoe and pumping in cement via the check valve float shoe and into the annulus.

Fig. 4 is an illustration of the float shoe.

Fig. 5 is an illustration of the drilling out of the float valve from the lower part of the conductor.

Brief summary of the Invention A solution to the above problems is presented in the invention. According to a first aspect of the present invention there is provided a subsea well (1) drilling method using a marine platform (2)comprising a drill floor (21) and one or more underlying decks (22, 23) such as an intermediate deck (22) and or a well head deck (23), each deck having a vertical passage or opening (211, 221, 231) for a drill pipe or casing string (3, 3S, 4), the method comprising: A: assembling and lowering a conductor casing string (4, 41) extending through said drill floor (21) and said underlying decks (22, 23), - said conductor casing string (41) provided with cementing ports (8) near said lower end (411); B: hanging off an upper end (412) of said conductor casing string (41) in a hangoff arrangement (26) near an elevation level (21L) of said drill floor (21), (Fig. 1) C: drilling a conductor well (1C) through said conductor casing string (41); D: arranging a drillpipe connectable float shoe (9) with check valves (91) in said lower end (411), said float shoe (9) provided with packers or swab cups (92) isolating said cementing ports (8); F: releasing said upper end (412) from said hangoff arrangement (26) and running said conductor (41) into said drilled conductor well portion (1C); G: connecting a drill pipe string to said conductor float shoe and injecting cement through said cementing ports (8) to cement the conductor / borehole annulus; H: allowing the conductor annulus cement to set and harden, and drilling out said conductor float shoe (9); and I: continuing drilling the well (2) for installing a first casing.

Advantages of the Invention

The method allows to run a conductor, such as a 28.00” conductor, to the seafloor open ended and hang it off near the drilling floor, e.g. on a spider-similar hang-off device 26. One may then drill through the conductor and use a so-called hole opener to increase the hole drilling diameter in order for the formed conductor borehole to receive the conductor. Once the conductor borehole is made one will continue to run the conductor to depth and install it in the borehole. The method provides a method of cementing the conductor in place with a float valve mechanism to hold back cement while it sets. An advantage provided by the method is that one may use a drillable float valve before lowering the conductor casing into the well. The float valve saves weight during insertion of the conductor. It may also save time after cement injection because one will not have to wait for settling of the cement in order to avoid U-tubing.

Embodiments o? the invention

Fig. 1 illustrates having assembled and lowered the conductor casing string (41) from near the drilling string and down to or near a well template. An upper end (412) of the conductor casing string (41) is held in a hangoff device (26), similar to a so-called "rotary" hangoff. A lower end (411) of the conductor casing string may extend all the way down to the drilling template, and is open-ended, and in this case will function as a guide pipe for the conductor drilling string. The lower end (411) may also extend to above the well template. Which of the two solutions depend on several factors such as the water depth.

Fig. 2 illustrates the first drilling step: A drill string comprising a drill pipe string (3) with a conductor drill bit (71) having an operating diameter of more than the outer diameter of the conductor pipe (41) is lowered through the conductor pipe and the well is spudded and drilled to the required depth for lowering the conductor into the conductor borehole.

Fig- 3a shows the conductor borehole formed to the required conductor depth with the conductor still hanging through the sea from the hang-off device (26).

Fig. 3b shows the drill string tripped out of the conductor pipe, and the conductor pipe having received a conductor float shoe (9) in its lower end (411).

Fig- 3c shows the hangoff device (26) having released the upper end (412) of the conductor pipe (41) and the conductor pipe having been lowered (suspended by e.g. drill pipe string) into its place in the conductor borehole.

Fig. 3d shows connecting a cementing string such as a drill pipe string to the float shoe and pumping in cement via the check valve float shoe, though the cementing ports in the lower end of the conductor pipe string, and into the annulus between the conductor pipe string and the conductor borehole wall. The check valve (94) will prevent the higher column of cement in the annulus to return back through the float shoe, so one need not necessarily maintain the pressure through the cementing string.

Fig. 4 is an illustration of the float shoe for use in the present method, provided with a check valve and cementing ports arranged between isolation packers or swab cups (92). The isolation packers or swab cups are for isolating the cementing ports in the conductor pipe wall of the lower section of the conductor pipe string. Key dogs (93) on the float valve are arranged for retaining the float valve engaged in ring grooves in the inner face of the lower portion of the conductor pipe.

Fig. 5 is an illustration of the drilling out of the float valve after setting and hardening of the cement in the conductor annulus. The drilling may now proceed below the cemented-in conductor for installing a first casing pipe.

After the conductor casing pipe has been cemented in place the well may be drilled further in a better controlled way using a riser pipe extending from below the drill floor to a seafloor BOP on said conductor casing. The first casing pipe extending within the conductor from the seafloor and further into the ground, usually to the bottom of the so far drilled well. The first casing pipe is then cemented into its annulus, and the further drilling proceeds likewise.

The float shoe may comprise drillable composites in order for easier drill-out.

Stated in a simplified manner, in a non-limiting embodiment, the method of the present invention comprises: - Hanging off a conductor casing from the drilling deck down through underlying decks to the seafloor. - Lowering the spudding drill string through the conductor and spudding the well for the conductor diameter, and retrieving the drill string. - Providing the conductor with a drillable float shoe arranged as a cementing tool for cementing through openings near the lower end of the conductor casing, said cementing tool portion having check valves. - Lowering the conductor into its desired position in the spudded well. - Connecting a cementing pipe string to said cementing tool float shoe. - Pumping cement via said cementing tool float shoe out into the conductor casing annulus, and retrieving said cementing pipe string and letting said cement settle and harden. - Drilling out said float shoe cementing tool and continuing the drilling operation.

Embodiments of the present invention have been described with particular reference to the examples illustrated. However, it will be appreciated that variations and modifications may be made to the examples described within the scope of the present invention.

Claims

1. A subsea well drilling method using a marine platform comprising a drill floor and one or more underlying decks such as an intermediate deck and or a well head deck, each deck having a vertical passage or opening for a drill pipe or casing string the method comprising: A: assembling and lowering a conductor casing string extending through said drill floor and said underlying decks, - said conductor casing string provided with cementing ports near said lower end; B: hanging off an upper end of said conductor casing string in a hangoff arrangement near an elevation level of said drill floor C: drilling a conductor well through said conductor casing string; D: arranging a drillpipe connectable float shoe with check valves in said lower end, said float shoe provided with packers or swab cups isolating said cementing ports; F: releasing said upper end from said hangoff arrangement and running said conductor into said drilled conductor well portion; G: connecting a drill pipe string to said conductor float shoe and injecting cement through said cementing ports to cement the conductor / borehole annulus; H: allowing the conductor annulus cement to set and harden, and drilling out said conductor float shoe; and I: continuing drilling the well for installing a first casing.

2. The method of claim 1, extending said conductor casing until a lower end of said conductor casing string is near or at the seafloor.

3. The method of claims 1 or 2,wherein step C comprises running in a conductor well drill string through said conductor casing, said conductor well drill string provided with a drill bit arranged with a drilling diameter for drilling a conductor well for receiving said conductor casing; and tripping out said drilling string.

4. A float shoe for use in the cementing of a conductor pipe string, the float shoe comprising: a check valve and cementing ports arranged between isolation packers or swab cups, wherein the isolation packers or swab cups are arranged to enable isolation of cementing ports in the conductor pipe wall of the lower section of the conductor pipe string.

5. A float shoe according to claim 4, comprising key dogs arranged for retaining, in use, the float valve engaged in ring grooves in the inner face of the lower portion of the conductor pipe.

6. A float shoe according to claim 4 or 5, wherein the float shoe is drillable.

7. The method substantially as shown in and/or described with reference to any one or more of Figures 0 to 5 of the accompanying drawings.

8. A float shoe substantially as shown in and/or described with reference to any one or more of Figures 0 to 5 of the accompanying drawings.