Wells – Processes – Disassembling well part
Reexamination Certificate
2000-01-18
2001-10-09
Bagnell, David (Department: 3672)
Wells
Processes
Disassembling well part
C166S077100, C166S085100, C405S146000, C405S150100
Reexamination Certificate
active
06298920
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to removal of rigid liners from within cylindrical cavities, and, more particularly, to the use of inflated liners to contact the cylindrical cavity while removing rigid liners.
BACKGROUND OF THE INVENTION
The installation of flexible supporting and sealing liners is described in U.S. Pat. Nos. 5,176,207, 5,803,666, and 6,026,900. In some cases, it is desirable to temporarily insert a rigid liner within a cylindrical cavity, such as a borehole, and to then replace the rigid liner with a flexible inflated liner with contact between the inflated liner and the cylindrical cavity during the replacement procedure.
However, if one inflates a flexible liner inside a rigid pipe of the same or less diameter, the flexible liner can not be easily withdrawn from the pipe, nor can the pipe be easily removed from off the flexible liner because of the excessive drag of the inflated flexible liner on the rigid liner. The pressure of the inflated flexible liner against the pipe wall and the large surface area of the pipe combine to produce very large drag resistance to sliding the pipe off the flexible liner. For example, a differential pressure of 1 psi in a 10 ft. long flexible liner inside a 4 in. diameter pipe, with a drag coefficient of 1.0, requires over 1500 lbs of force to pull the inflated liner out of the pipe. Such a large force may tear the flexible liner. As the pipe length increases to that of common well depths, the larger drag force is certain to tear the flexible liner.
It is common practice to emplace a rigid liner (e.g., a pipe) to support a drill hole wall while drilling a well. It may then be useful to replace the rigid liner support of the hole wall with the support of an inflated flexible liner. However, if the inflated liner is anchored to the bottom of the hole, and one pulls upward on the rigid liner, the drag of the rigid liner on the inflated liner prevents the rigid liner from being removed from the hole without a potentially destructive drag force on the flexible liner.
The present invention eliminates most of the drag force of a rigid liner on the inflated liner without the use of a lubricant to reduce the friction coefficient.
Various objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
SUMMARY OF THE INVENTION
In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes apparatus for continuously contacting a cylindrical cavity while removing a rigid liner from within the borehole. The apparatus includes a flexible liner insertable within the rigid liner, having an expanded diameter greater than a diameter of the borehole, and having a top end and closed bottom end. A hollow conduit is attached to the bottom end of the flexible liner and has an opening adjacent the bottom end for introducing a fluid to expand the flexible liner against the cylindrical cavity and contact the cylindrical cavityl as the rigid liner is withdrawn from about the flexible liner.
In another characterization of the present invention, a cylindrical cavity is continuously contacted while removing a rigid liner from within the cavity. A flexible liner is inserted within the rigid liner, the flexible liner having an inflated diameter greater than the cavity diameter and forming an annulus with the rigid liner. The flexible liner is first filled with a fluid. The annulus between the rigid liner and the flexible liner is then filled with a fluid to equalize with the pressure of the fluid within the flexible liner. The rigid liner is withdrawn from the cavity while adding fluid to maintain the fluid level within the flexible liner as the flexible liner expands against the cavity as the rigid liner is withdrawn.
REFERENCES:
patent: 2998065 (1961-08-01), Hildebrandt
patent: 5044405 (1991-09-01), Driver et al.
patent: 5119862 (1992-06-01), Maimets et al.
patent: 5803666 (1998-09-01), Keller
patent: 5816345 (1998-10-01), Keller
patent: 5853049 (1998-12-01), Keller
patent: 6026900 (2000-02-01), Keller
patent: 6129199 (2000-10-01), Schwert et al.
Bagnell David
Dougherty Jennifer
LandOfFree
Method and apparatus for removing a rigid liner from within... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for removing a rigid liner from within..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for removing a rigid liner from within... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2607347