Innovation in Technology Series

Perfed the Wrong Zone? Finding Wells with Untouched Pay: Interview with Teddy Pledger

American Association of Petroleum Geologists (AAPG)

In addition to bypassed, stranded, or overlooked pay, there is also pay that was left behind because the well was perforated in the wrong zone, thanks to a phenomenon known as "pipe creep." Teddy Pledger talks to us today about the potential for new production in wells in which the perfs might have missed the best part of the pay. It could be an excellent opportunity for enterprising geologists, especially if they team up with a petrophysicist.

What is your name and your relationship to the oil industry?

My name is Teddy M. Pledger. I graduated from LSU with a BS degree in Petroleum Engineering. Since 1976, I have spent much of my time teaching seminars to the industry around the world. My greatest area of expertise is in Completions and Workovers.

What is "pipe stretch" or "creep"?

"Pipe stretch" or "pipe creep" is referred to mainly in drilling horizontal wells. "Wireline creep" is the downhole movement of wireline equipment that occurs after the winch is stopped.

Why does it matter?

If there is wireline creep in a well and it is neglected, it results in the wireline tools being higher in the well than planned.

How can creep affect the completion? Are the perfs in the wrong place?

This can result in wireline cores being taken from a higher position than desired and can result in errors about the formation that was to be sampled. The same is true for formation test tools. Packers, bridge plugs, cement retainers, etc. will be higher in the well than planned. Perforations will be higher than desired and could result in completely missing the pay zone. Companies that add radioactive tracers to frac fluids report that perforations are higher than the perforating record indicates.

The article I wrote for World Oil Magazine, (January issue, 2008, page 61) gives several examples of wells where wireline creep had a great impact on the completion.

Do you know of wells that were mis-perfed? Would this make a good package for someone wanting to drill low-risk wells? How? How would you get started?

This would surely open the door for low risk reentries, or redrills to zones that are good from the open hole logs, but were missed in the perforating process because of creep.

To get started, a person would have to search well log files, ask people. especially geologists, if they know of any wells that looked great on the logs, but attempted completions failed to result in production. The best place to look would be deep wells that had thin pay zones. The greater the depth, the greater the amount of creep.

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