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Cementing Plug with Jetting Nozzles

IP.com Disclosure Number: IPCOM000132525D
Publication Date: 2005-Dec-20
Document File: 6 page(s) / 161K

Publishing Venue

The IP.com Prior Art Database

Abstract

A cementing plug having a jetting nozzle configuration and improved wiping characteristics. The cementing plug has a plug subassembly with a body member and an elastomeric jacket on the body member. The cementing plug has a shearable insert (rupture disc) positioned on the lower end so that when the bottom plug lands at the bottom of the casing, the shearable insert will shear at the predetermined pressure. The shearable insert is one of a plurality of such inserts designed to shear at correspondingly different shear pressures. The jets may be configured on a rotational disc at the lower end of the plug thus creating a circular jetting motion.

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Cementing Plug with Jetting Nozzles

ABSTRACT:

A cementing plug having a jetting nozzle configuration and improved wiping characteristics. The cementing plug has a plug subassembly with a body member and an elastomeric jacket on the body member. The cementing plug has a shearable insert (rupture disc) positioned on the lower end so that when the bottom plug lands at the bottom of the casing, the shearable insert will shear at the predetermined pressure. The shearable insert is one of a plurality of such inserts designed to shear at correspondingly different shear pressures. The jets may be configured on a rotational disc at the lower end of the plug thus creating a circular jetting motion.

INTRODUCTION:

In the cementation of casing in oil wells, the need to effectively remove mud cake that adheres to the casing ID is critical to the success of the cement job. The removal of this filter cake and other debris from the casing ID is to help ensure a good bond is obtained between the casing, cement and formation. If this debris is not removed by a bottom plug cement contamination can occur.

This paper describes a method & apparatus/mechanism that creates a fluid jetting action ahead of the cementing plug wipers that greatly increases the cleaning efficiency of the plug.

PROBLEM WITH PRIOR ART - CURRENT TECHNOLOGY

The problem with prior art is that sometimes the velocity of the cementing plug (bottom plug in particular) can exceed the elastomeric reflex time of the cementing plug wipers. This situation is most predominate in small diameter/long strings casings when the well is on a "screaming" vacuum or when the job is a "pump until you bump" style job. The velocity of the plugs creates a situation similar to hydaplaneing in the casing itself and particularly when passing a threaded and coupled collar.

A demonstration of this phenomenon can be observed by lightly grasping the end of a squeegee and rapidly pulling it across a wet irregular surface. The squeegee will "skip" across the surface leaving streaks of moisture.

Consequently if the squeegee is pulled more slowly across the surface a more effective wiping effect is observed due to the fact that the rubber has time to elastomerically relax to contour to the irregularities.

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See attached schematic for a graphical representation of the problem.

Skipping Phenomenon When Passing Collars

OBJECTIVE:

The objective of this disclosure is a method & apparatus/mechanism that creates a fluid jetting action ahead of the cementing plug wipers that greatly increases the cleaning efficiency of the plug. The uniqueness of this new design is that there is a series of jetting holes on the lower most portion of the bottom cementing plug. The plate has several off set holes that allow fluid to pass through. The holes are off set and tapered to act as a jet nozzle when fluid is being pumped. The jet nozzles will help loosen the debris from the inside of the casing and the plug will wipe the ex...