Well plug and abandonment choke insert

Abstract

A process for plugging a wellbore comprises installing a choke device (1) into the wellbore to increase the back pressure allowing better control when introducing cement to plug the wellbore. The device (1) has a cylindrical shape with a central through bore (6). On the external profile is a shoulder (4) which, when the device is installed in a wellbore, comes to rest against a nipple in the wellbore. The device (1) may free fall for all or part of the way down but would normally be pumped down at least for the last part of its delivery. In the bore (6) is a pump out ball (10) which blocks the through bore until the device reaches the nipple and stops, at which point pressure increases and the ball is ejected. Cement and other liquid may then be pumped through the choke device to the distal region of the well.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a non-provisional application which claims the benefit of and priority to U.S. provisional application Ser. No. 61 / 447,789 filed Mar. 1, 2011, entitled “Well plug and abandonment choke insert,” which is hereby incorporated by reference in its entirety.FIELD OF THE INVENTION[0002]This invention relates to a method and apparatus for plugging a wellbore (such as e.g. an oil or gas well), or for preparing wellbore to be plugged, e.g. when it has reached the end of its productive life. The invention also relates to a plugged wellbore.BACKGROUND OF THE INVENTION[0003]When an oil or gas well is no longer economical or if there is some problem with the well which means that production is no longer possible or that well integrity has been compromised in some way, or for other reasons, the well may be abandoned. It is common practice to plug the well before abandoning it, e.g. to prevent seepage of hydrocarbon product from the w...

AI Technical Summary

Benefits of technology

[0014]The invention more particularly includes a process for plugging a wellbore wherein the process comprises the steps of (a) installing a choke device into the wellbore, the device having a through bore with a

Problems solved by technology

When an oil or gas well is no longer economical or if there is some problem with the well which means that production is no longer possible or that well integrity has been compromised in some way, or for other reasons, the well may be abandoned.

In many cases, the bottom hole pressure is insufficient to support a standing column of relatively high specific gravity liquid reaching to the top of the well.

In this event, positive pressure against the fluid column at the surface cannot be maintained as liquids are introduced into the top of the well.

This results in liquid free falling down the wellbore and out through the reservoir completion, i.e. the perforated section of casing / liner.

In this situation, it is often not possible to monitor when the cement has reached the desired wellbore location with respect to the perforations which it is desired to seal.

Without an accurate understanding of where the cement is, it is possible to over-displace the cement by continuing to introduce fluid at the surface which freefalls and over displaces the cement, with the result that the proximal perforations are not effectively squeezed.

Partly closing perforations with solid material can be undesirable since the perforations can end up not adequately plugged.

Conversely, because there is little control over the degree of plugging and at which point it will occur, an undesirable outcome can result if all perforations are plugged off with medium prior to achieving designed displacement.

However, there is a limit in available low specific gravity fluids and the constituents incorporated in them that meet design requirements.

Images