Method and system for wireline intervention in a subsea well from a floating vessel

Abstract

A method for wireline intervention in a subsea well from a floating vessel.

Claims

1. A method for wireline intervention in a subsea well from a floating vessel, the method comprising: a) arranging a tubular tool riser in a substantially horizontal position at a deck of the vessel; b) connecting a wireline assembly to a wireline that is connected to a winch arranged at the deck; c) inserting the wireline assembly and passing the wireline through a first end of the tubular tool riser such that the wireline passes along a riser sheave connected to the first end of the tubular tool riser; d) connecting the first end of the tubular tool riser to a crane that lifts the tubular tool riser in a substantially vertical position above the deck, whilst unreeling the wireline from the winch such that the wireline assembly remains located within the tubular tool riser; e) inducing the crane to move a second end of the tubular tool riser above a guide sleeve which is attached to a work platform cantilevered off a side of the vessel; f) inducing the crane to lower the tubular tool riser through the guide sleeve such that the second end of the tubular tool riser is located subsea and the first end of the tubular tool riser and the riser sheave are located above the deck; and g) inducing a crane heave compensation mechanism to control the motion of the tubular tool riser and riser sheave relative to the seafloor while unreeling the wireline from the winch such that the wireline assembly is lowered from the tubular tool riser through the water into the subsea well.

2. The method of claim 1, wherein the first end of the tubular tool riser is connected by a hoisting cable to a hook which is connected to a fall line of the crane.

3. The method of claim 2, wherein the hook is connected to a single fall line of the crane and the crane heave compensation mechanism is configured to maintain the hook substantially stationary relative to the seafloor, thereby providing heave compensation to the wireline assembly.

4. The method of claim 2, wherein wireline passes through a deck sheave which is connected to the deck adjacent to the sleeve and the hook is connected to a hoisting sheave which is connected by a double fall crane line to the crane.

5. The method of claim 1, wherein the wireline assembly is inserted into the subsea well.

6. The method of claim 5, wherein the wireline assembly is first lowered into the subsea well and subsequently pulled up through the well at a predetermined speed by winching up the wireline while activating monitoring equipment in the wireline assembly.

7. A system for wireline intervention into a subsea well from a floating vessel, the system comprising: a) a floating vessel having a deck configured to support a tubular tool riser in a substantially horizontal position; b) a winch at the deck which is configured to be connected to a wireline and wireline assembly; c) means for inserting the wireline assembly and passing the wireline through a first end of the tubular tool riser such that the wireline passes along a riser sheave connected to the first end of the tubular tool riser; d) a crane that is configured to be connected to the first end of the tubular tool riser and to lift the tubular tool riser in a substantially vertical position above the deck, whilst unreeling the wireline from the winch such that the wireline assembly remains located within the tool riser; e) means for inducing the crane to move a second end of the tubular tool riser above a guide sleeve which is attached to a work platform cantilevered off a side of the vessel; f) a crane control mechanism for inducing the crane to lower the tubular tool riser through the guide sleeve such that the second end of the tubular tool riser is located subsea and the first end of the tubular tool riser and the riser sheave are located above the deck; and g) a crane heave compensation mechanism for controlling the motion of the tubular tool riser and riser sheave relative to the seafloor while unreeling the wireline from the winch such that the wireline assembly is lowered from the tubular tool riser through the water into the subsea well.

8. The system of claim 7, wherein the first end of the tubular tool riser is connected by a hoisting cable to a hook which is connected to a fall line of the crane.

9. The system of claim 8, wherein the hook is connected to a single fall line of the crane and the heave compensation mechanism is configured to maintain the hook substantially stationary relative to the seafloor, thereby providing heave compensation to the wireline assembly.

10. The system of claim 8, wherein wireline passes through a deck sheave which is connected to the deck adjacent to the sleeve and the hook is connected to a hoisting sheave which is connected by a double fall crane line to the crane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic side view of a first embodiment of a system according to the invention; and

(2) FIG. 2 is a schematic side view of a second embodiment of a system according to the invention.

DETAILED DESCRIPTION OF THE DEPICTED EMBODIMENTS

(3) The system according to invention shown in FIGS. 1 and 2 includes the following two inventive features I and II:

(4) I) The tool riser 1, which is a long joint of pipe with a quick connection flange welded to the first end of the riser 1A and a bevelled opposite end (second end of the riser 1B). The tool riser 1 provides a means for the wireline toolstring 7A to be assembled in horizontal position into the tool riser 1 with the support of a work table, safely upended from horizontal to vertical position and finally deployed subsea. As soon as the tools are assembled and secured to the toolstring 7A they are inserted into the tool riser 1 through a quick connection flange at a first end 1A of the tool riser 1. Then the tool riser 1 is upended using a crane hook 2 and dedicated slings 3 connected to the first end 1A of the tool riser 1. This upending method does not offer any risk or damage to the tool strings 7A to be deployed.

(5) II) The tool riser 1 is suspended by an active heave compensated crane hook 2 of a crane (not shown) mounted on the deck 4A of a floating vessel 4. When the heave compensation system on the crane is activated, the tool riser 1 is raised and lowered relative to the deck 4A of the floating vessel 4 keeping the tool string stationary relative to the seafloor, effectively isolating vessel motions from the tool string. As the wireline 7, which may comprises power and control cables or be a slickline without power and control cables, passes through the riser sheave 8 on the tool riser 1, compensation is transferred to the wireline 7.

(6) The tool riser 1 moves up and down through a guide sleeve 5 attached to a work platform 6 cantilevered off the side 4B of the vessel 4. The sleeve 5 allows vertical motion of the tool riser 1, but prevents motion of the tool riser 1 in the horizontal plane. The arrangement of the tool riser 1 through the sleeve 5 prevents the tool riser 1 and crane hook 2 from swinging uncontrollably due to oscillating motions of the vessel 4 due to waves, wind and/or current.

(7) The tool riser 1 extends through the splash zone 9 into the water 11, which may be a sea, ocean or lake to protect the fragile toolstring 7A from damage due to wave action at the water surface.

(8) There are two possible sheave arrangements that can be utilized depending on available deck space on the vessel 4 of opportunity.

(9) FIG. 1 shows the simple sheave arrangement, which arrangement requires more deck area than the more complex sheave arrangement shown in FIG. 2.

(10) Wireline operations on traditional drilling rigs compensate the toolstring 7A in a similar manner.

(11) In FIG. 1, the crane hook 2 is suspended from a single fall crane line and is attached to the tool riser 1 by the slings 3 and operated in conventional heave compensation mode. The distance from the wireline winch 7B to the riser sheave 8 connected to the first end 1A of the tool riser 1 must be sufficient that when the tool riser 1 moves up and down with the crane hook 2 the change in distance between the wireline winch 7A and the tool riser 1 is negligible.

(12) FIG. 2 shows an alternate sheave arrangement which has been successfully used for an offshore well intervention. The crane hook 2 is connected to a double fall block 20, but the heave compensation system of the crane is operated in single fall mode. Therefore, the crane block 20 and hook 2 are only moving up and down half as much as they would normally move when the heave compensation system is activated. The movement on the crane block 20 and hook 2 is then multiplied by a factor of two with the sheave arrangement of a fixed sheave 21 on the work platform 6 and the riser sheave 8 on the tool riser 1, and the toolstring 7A is properly heave compensated at the seafloor. This arrangement can be used when there is a limited horizontal distance between the wireline winch 7B and the tool riser 1.

(13) It allows wireline operations to be performed from any vessel 4 of opportunity equipped with an active heave compensated crane hook 2 using a conventional wireline winch.