Universal cementing plug

Abstract

A cementing plug having a universal construction and improved wiping and extended wear characteristics. The cementing plug has a plug subassembly with a body member and an elastomeric jacket on the body member. The body member defines a central opening therethrough with a shoulder therein. To configure the plug as a bottom cementing plug, a shearable insert is positioned on the shoulder, and to configure the plug as a top cementing plug, a non-shearable insert is positioned on the shoulder. The shearable insert is one of a plurality of such inserts designed to shear at correspondingly different shear pressures. In a first embodiment, the shearable insert is a substantially flat disk having a uniform thickness, and in a second embodiment, the shearable insert has an outer ring portion and a relatively thin inner domed portion. Thus, a bottom plug may be pumped down a well casing with cement and a top plug thereabove so that when the bottom plug lands at the bottom of the casing, the shearable insert will shear at the predetermined pressure. The jacket has one or more wiper cups which have a conical surface extending at an acute angle with respect to a longitudinal axis of the plug, thereby providing a substantially large contact area in the well casing to improve wiping efficiency and extend life.

Description

CROSS REFERENCE[0001]This application is a continuation of U.S. patent application Ser. No. 09 / 970,432 filed Oct. 3, 2001 which is a reissue of U.S. patent application Ser. No. 09 / 175,664 filed Oct. 20, 1998, now U.S. Pat. No. 6,196,311 which issued on Mar. 6, 2001. This application is related to U.S. patent application Ser. No. 10 / 307,113 filed Apr. 10, 2003(now abandoned) and U.S. patent application Ser. No. 11 / 267,892 filed Nov. 4, 2005 both of which are divisional of U.S. patent application Ser. No. 09 / 970,432 filed Oct. 3, 2001. <?insert-end id="INS-S-00001" ?>BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates to cementing plugs for use in cementing casing in a well, and more particularly, to a universal cementing plug having improved wiping and extended wear and which includes a plurality of interchangeable inserts so that the plug may be selectively used as a top or a bottom plug.[0004]2. Description of the Prior Art[0005]In the proce...

AI Technical Summary

Benefits of technology

The present invention is a universal cementing plug that can be used in cementing casing in a well. The plug has a body with a central opening and an elastomeric jacket with a wiper cup for engaging the inner surface of the casing. The plug can be used as a bottom plug or a top plug, with different inserts being used for shearing or permanent closure of the central opening. The plug has a conical surface that deflects into a cylindrical shape to provide a large wiping surface and extended wear life. The invention also includes a cementing plug apparatus with two body members and two replaceable disks for temporally or permanently closing the central opening. The invention provides improved wiping and increased wear in well cementing operations.

Problems solved by technology

This causes a normal pressure rise at the surface and notifies the operator that the cementing job is complete.

Because each plug requires different construction, separate molds must be used for each of the plugs which increase the costs of manufacturing, and also, the two separate plugs must be kept in inventory.

With prior art cementing plugs, the wiping efficiency of the wipers on the plugs is affected by pumping rate and wear along the casing surface.

As a top cup on the plug wears, the pressure is transferred to a bottom cup which prolongs the surface engagement maintaining the wiping, resulting in extended wear.

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