But employing directional drilling in this case was no easy feat. The project--which would consist of two challenging bores--posed several heady problems for would be contractors--problems that inevitably chased all but one away.

Of primary concern was drilling the pilot hole from inside the basement of the new building to the existing building. This means lowering a drill rig into the basement--and lifting it out once the job was finished. A challenge beyond the drilling. At the other end, a hole would have to be made in the basement wall so that the bundle of seven 4-in. (100-mm) SDR 11 HDPE conduit could pass between the buildings. Also of concern was removal of the drilling fluid because of the basement location. 

And, oh yeah, don't disrupt the timeline set by the project owner, Mellon Bank, and project developer, Gilbane Properties. The building is scheduled for completion this December.

Piece of cake.

Tom and Jason Hockran--the father/son team that make up H&H Enterprises in Andover Ohio--believed they could do this job. And do it well.

"There were a lot of people who were skeptical that it could be done." Jason Hockran said. "There was too much risk involved."

Simply put, people thought the Hockrans were crazy to try it.

"I took one look at it and thought, "'Man, why would they bother.'" said Jay Miller, sales manager for INROCK Guidance Systems who handled the steering and guidance systems on the second bore. INROCK supplied the steering and drilling tools for the project.

From a guidance standpoint, this would prove to be an extremely difficult job for INROCK because of the tight curves that would have to be made.

"When I actually saw the job, I didn't think it could be done," Miller said.

For the job, the Hockrans chose an American Augers DD-6 drill. Because the rig was brand new, H&H was trained on it on-site by DJ Miller of American Augers, who drilled the first bore. Arrangements were made for a crane to lower the 23,000-lb (102-kN) rig some 45 ft (13.5m) through an elevator shaft to position it in the basement to drill the pilot hole for the first bore. INROCK supplied a Black Max 3 3/4-in. (94-mm) mud motor and a Tensor steering tool system with TruTracker to drill this crossing.

This bore--850 ft (257.5m)--would be made through the basement's 3-ft (1-m) thick wall. Ground conditions for the bore were solid rock--soft sandstone. The pilot hole was 5 1/4 in. (131mm) in diameter and would later be enlarged to 22 in. (550mm) for the conduit. After the pilot bore reached the existing building, a 30-in (750-mm) hole was made in the basement's wall so the bundle of conduit could pass through.

INROCK technicians brought the drill bit within 6 in (150mm) of the planned exit point. After three days, the pilot bore was done.

Problems surfaced when the pilot hole was being enlarged. About 720 ft (218m) into the first pre-ream, the 12 1/4-in. (306-mm) mill tooth hole opener hit a steel obstruction that was later determines to be an old steel pylon. The hole opener the Hockrans were using couldn't cut the steel, so they rented a 12- and 22-in. (300- and 550-mm) mill reamer from Baker Hughes Oil Tools. It took five days of tripping in and out of the hole to complete the milling of the steel.

For the removal of the drilling fluid, H&H chose an American Augers MCM 1800 recycling system and employed some ingenuity. Of primary concern were possible frac-outs into other basements and containing the fluid in the existing building.

To solve the latter problem, the Hockrans rented two twin 27 vac trucks from UVAC Inc. to suck out the fluid from the second basement level of the old building. The trucks were connected by two 6-in. (150-mm) hose liners, which ran along the same path as the conduit. A temporary tank was constructed at the exit hole to contain the fluid.

Bore #2

The second bore, drilled by Tom Hockran, was launched from a vacant lot and traveled 450 ft (136m) to the second basement level of the existing building. To onlookers, this bore may not have the visual drama of lowering a drill rig into an elevator shaft, it was nonetheless as complicated.

This bore consisted of very tight, extreme curves that were precisely navigated by Jay Miller, who was on-site for this portion of the job. The bore was drilled in an S-shaped curve between buildings. The turns consisted of 26 degrees on a 250-st (76-m) radius to the right and 26 degrees on a 300-ft (91-m) radius to the left to get to the existing building.

While drilling the pilot hole, the crew went about 8 ft (2.5m) when it hit the concrete foundation of an old building. The obstruction, about 2 ft (.5m) thick, was removed using a jackhammer. The next day, the crew drilled about 80 ft (24m) when another obstruction was hit Magnetic indicators showed it to be made of steel.

"Our concern was that it may have been a pipeline." Jay Miller said.

It wasn't. The obstruction was determined to be a steel support beam, which as Jay Miller stated "we hit dead in the middle" with a 5 1/4-in (131mm) TCI tricone drill bit. A Black Max 3 3/4-in. (94-mm) mud motor was also used.

The beam was cut and a 30-in. (750-mm) steel casing was installed to protect the conduit during the pullback. Unlike the first bore, a mud motor was not used to get through the basement wall (the Hockrans didn't want to pump any more drilling fluid into the foundation.)

Instead, a mark was placed on the wall where the drill head was supposed to exit and a 12-in. (300-mm) test hole was drilled into the wall to find it. How successful was the bore?

"It was right where Jay [Miller] said it would be." Jason Hockran said.

Once the hole was placed in the basement foundation, the conduits were snaked through the building and attached to the end of the drill stem. Because of hole instability, the Hockrans decided to trail rods behind the reamers on the first pass. However, about 85 percent of the way back, the rods stopped moving: the back of the swivel had come unscrewed from the back of the reamer, leaving 350 ft (106m) of rods in the ground.

H&H had two choices to retrieve the rods: winch them out by hand or rent a fishing tool to snag and pull the pipe back through the hole. The latter option was chosen. H&H rented an overshot bit from Baker Hughes Oil Tools and Tom Hockran fished out the stranded pipe and reeled it back in.

And they were done. H&H was awarded this job in July 1999. Drilling for the first bore started on Aug. 31, 1999 and it was completed Sept. 29. The second bore finished up at the end of October.

Looking back on the job, the Hockrans and Jay Miller said they never had an experience quite like this.

"It was a real mental challenge. You had to be creative," Miller said. "Hats off to the Hockrans to coordinate all of this."

"It was interesting to say the least," Jason Hockran said.

Sharon M. Bueno is managing editor of Directional Drilling.