130° Lateral Turn
Tight radius lateral turns are possible using sophisticated HDD techniques. Our design and drilling in Connecticut included a 130 degree lateral turn to install communications cable.
• And The Two Became One • by Ron Adams
In October 1992, Environmental Crossings, Inc. (ECI) of Traverse City, MI, began a drilled crossing project for Connecticut Cable Construction & Maintenance, Inc. of Middlefield, CT. Project owner was Cox Greater Hartfort CATV. The scope of the project was to directionally drill two crossings (one with a sharp lateral turn) via trenchless technology and leave a 5 in. O.D. conduit in place for fiber optic transmission cables. The crossings were to share the same exit point into a planned manhole.
The highway intersection crossing work was part of a larger 8000 foot fiber optics installation contract performed by Connecticut Cable Construction. ECI completed about 3800 feet of directionally installed conduit in which they pulled back 4 in. multi-cell pvc duct for the fiber optics cable.
By using computer software developed by CBC-Welnay, ECI planned the directional crossing profiles. Profile #1 called for a basic approach: 1) Use a slant rig; 2) Directionally drill down & horizontal; 3) Come up and out of the ground in a straight line from entry point. Profile #2, however, was a lot more innovative and optimistic. It required a grade change from 12 degrees to +10 degrees with a 130 degree lateral turn within 10000 lineal ft. of the drilled hold.
The complexity of this project was in the drilling of profile #2. The jet-bit had to be navigated in a three dimensional plane. This type of project has only been approached by oilfield drilling, where no exits are involved and targets are much larger. Therefore this project was unique for two reasons: 1) 130 degree lateral turn; 2) accuracy of the drilled path to target.
According to the profile, the first few joints of drillpipe were actually drilled away from the target. The downhole jet-bit drilling assembly performed as predicted, and the curve began to take shape. The soft formation allowed for a fast penetration rate, but ECI kept the drilling speed and radius of curvature (dog-leg) in check, since profile #2 was approaching the bending limits of the drillpipe and the downhole drilling assembly. On Oct. 9th., the jet-bit exited on target 1000 ft. from the drill rig and joined up with the first phase crossing at the planned manhole site.
The crossing for Profile #2 was a medium-length lateral crossing, but the 130 degree lateral turn is believed to be a world record.
"There were plenty of nay-sayers. Even drilling professionals who stood on the site and said: It couldn't be done. But you will never finish, if you don't start something! ECI delivered the project and came in under budget," said Doug Allman, ECI's vice president-engineering and project engineer for the Connecticut Cable crossing.
Charles Ferrara, President of Connecticut Cable Construction & Maintenance commented: " I was very amazed and very grateful for ECI's job performance! The alternatives would have been two to three times more expensive than the directional drilling."
Ferrara mentioned that he had had three different contractors look at the project design: One said it couldn't be done; Another doubted that it would be possible; The third was ECI, and they completed it as planned.
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