Wells – Processes – With indicating – testing – measuring or locating
Reexamination Certificate
1998-11-25
2001-07-17
Lillis, Eileen D. (Department: 3673)
Wells
Processes
With indicating, testing, measuring or locating
C166S255100, C166S255200, C166S255300, C073S152590, C073S152170
Reexamination Certificate
active
06260618
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to oil well tools. More particularly the invention relates to proper placement of a guide stock in a wellbore for diverting tools into a lateral borehole.
2. Prior Art
When a lateral borehole is to be drilled a certain sequence of events is known and practiced regularly. First a packer is set within a primary wellbore at a location downhole of the desired exit point for a lateral borehole. A whipstock is then run and inserted in the anchor, the whipstock having an orientation sub thereon which orients the face of the whipstock in the desired direction of the proposed lateral borehole. A drill is run and the lateral borehole created. The drill is removed, the whipstock is removed and a guide stock is stabbed into the original packer. Since the guide stock is provided with the same type of orientation sub it orients in the same direction that the whipstock originally did. This is an old and well-known sequence of events and would seem to indicate that the diverter face of the guide stock should be aligned with the lateral borehole. Unfortunately, however, during the kicking off of the drill from the whipstock, the whipstock tends to move due to the tremendous torque placed on the whipstock by the drill. Since the whipstock is in this (contorted to some degree) condition when the drill leaves the primary bore the exact angle and orientation of the window thereby created is somewhat different than planned. The movement does not translate to the packer and so when the whipstock is replaced by a guide stock for feeding other tools into the lateral borehole, it may not be aligned. The orientation of the guide stock, not having any torque loads thereon is that of what was originally planned and may not coincide with the actual orientation of the lateral borehole itself. For this reason it has always been challenging to properly orient the guide stock to align with the lateral borehole.
Prior art methods for aligning the guide stock include, as the most common and ubiquitous method, experience of the drill team. More specifically, upon removing the whipstock from the hole an inspection is made which to a skilled and experienced eye will indicate about how far off the planned orientation the lateral borehole has been drilled. This is accomplished by examining marks made on the whipstock by the drill bit such as how deep the marks are, where on the diverter face the marks are located, etc. These marks tell the experienced driller where the bit bound and kicked off the whipstock diverter face and thus in which direction drilling began. From these determinations the drill team will reorient the guide stock by attaching the orientation sub to the guide stock differently. This modifies the orientation of the diverter surface so as to be more likely to be aligned with the lateral borehole. While skill and experience are of the most important assets in making a well work, the guestimate method of placing a guidestock leaves exactness to be desired.
SUMMARY OF THE INVENTION
The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by the method and apparatus for placing a guide stock of the invention.
A guide stock can be reliably and precisely placed and aligned with respect to a lateral borehole by first obtaining an impression of the actual borehole window through the casing of the primary well including its exact orientation with an impression packer having an orientation sub attached thereto for engagement with the original packer installed in the primary well in preparation for drilling the lateral borehole. Upon inflation of the impression packer, the soft casing is urged into the lateral borehole opening and an impression of the window is recorded in the soft covering on the impression packer. The impression packer is then tripped out of the hole and can be reinflated at the surface to measure the impression of the lateral borehole. The impression is an exact duplicate showing angle, orientation, chord length, etc. of the window. Armed with this information a guide stock may be specifically tailored with an orientation sub and space-out subs to perfectly align with the lateral borehole. Enhancing the ability to measure the window impression is the act of scribing a line in the impression cover to employ as a reference.
In another aspect of the invention an impression packer having its own inflation reservoir is disclosed. While a standard impression packer known to the prior art may be employed in the method of the invention, certain inherent drawbacks exist. Although standard impression packers regularly function correctly, there are times when inflation is not completed or deflation is not possible. This is generally due to the employment of a rig pump at a great distance from the tool to inflate the tool and the length of the fluid column with respect to deflation. For preferred employment with the method of the invention is an impression packer having its own on-board inflation source.
The self-inflation impression packer of the invention provides more certainty that the packer will inflate to the desired pressure (approximately 200 psi) without significantly exceeding that pressure and will deflate reliably and without difficulty. The self-inflation device carries a predetermined quantity of inflation fluid which is urged into the element upon set down weight. The device automatically deflates the impression packer upon pick up. The arrangement avoids prior art inflation and deflation problems associated with pressuring up from the surface to deploy the packer. In another embodiment of the invention, the over pressure problem is avoided by installing a valve which closes at a specific predetermined pressure rating (e.g. 200 psi). A valving system is disclosed.
The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.
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Lynes Technical Manual, Feb. 4, 1977.
Davis John P.
Roddy Jim H.
Wood Edward T.
Baker Hughes Incorporated
Cantor & Colburn LLP
Lillis Eileen D.
Singh Sunil
LandOfFree
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