Its Ok to fail but don't accept being second best.
Joined: Jun 2003 Gender: Male Posts: 197 Location: Scotland
Bit position when jetting? Ooot or in? « Thread Started on Oct 27, 2009, 6:53am »
I am in the porcess of updating a jetting conductor best practices document I compiled many years ago.
Through time I have seen bits place anywhere from 1ft inside to 6" to 1ft outside conductor shoes and have had several conversations at to the whys and what fors. Namely being driven by type of sediments and charachtersitics present.
However as I didn't write comments down and as my memory is deteriorating with age can club members please remind m what they know in this respect.
Note: Document will be available on line if I ever get my site back up andrunning where I am having numerous IT problems.
Joined: Jun 2003 Gender: Male Posts: 188 Location: PERTH WESTERN AUSTRALIA
Re: Bit position when jetting? Ooot or in? « Reply #1 on Oct 27, 2009, 8:55am »
Recent experience tells me to run the bit 4"- 6" inside the 30" drive. I was using a CADA tool. When the bit was outside, the Bit drilled a 26" hole leaving a ledge that was able to support the weight of the casing. Nothing that bit does is able to attack this ledge. It spins wildly but can not dig. The formation below the bit may washed out by the jetting action. Still the conductor is resting on the ledge. Conversely, when the bit was inside, the drive shoe lip was able to be under-scoured by the hydraulic jetting action. This scouring allows the Casing to drop minutely but it doe progress. If the bit is too far inside the jetting action is inconsequential.
Re: Bit position when jetting? Ooot or in? « Reply #2 on Dec 28, 2009, 4:52pm »
I would suggest keep the bit stick out = 15 cm -25 cm outside CP. I hope that would avoid the problem Holdril has mentiond above about forming a ledge.
Joined: Jun 2003 Gender: Male Posts: 188 Location: PERTH WESTERN AUSTRALIA
Re: Bit position when jetting? Ooot or in? « Reply #3 on Dec 29, 2009, 6:48am »
Having the bit outside is what forms the supporting ledge. If you keep the bit inside the drive shoe then jetting can continue until the shoe is able to support the full weight of the shoe. This is the aspiration. We do not want to have the shoe hung up on a ledge caused by the smaller diameter bit drilling ahead of the shoe. Bit position while jetting should be inside the casing.
![[image]](http://www.drillfloor.com/the%20driller%27s%20club.jpg)
![[Search This Thread]](http://s4.images.proboards.com/search2.gif)
![[Send Topic To Friend]](http://s4.images.proboards.com/buttons/sendtopic.gif)
![[Print]](http://s4.images.proboards.com/buttons/print.gif)
Author
![[avatar]](http://s4.images.proboards.com/avatars/angryboy.gif)
![[msn]](http://s4.images.proboards.com/msn.gif)
can club members please remind m what they know in this respect.
Logged
