The drilling mud, which is constantly pumped down the pipe, is used as a source of power to turn the bit.Ī short distance back from the bit, there is an “elbow” in the pipe. Instead, only the drill bit at the front end of the drill pipe is rotated. In order to be able to change the direction of drilling, the drill pipe cannot rotate as it does in traditional drilling. Two additional features are added, for changing direction and for monitoring the drill’s location underground. HDD, as I learned, is a refined version of that process. The mud flowed back up the hole and emerged around the drill pipe, bringing with it bits of rock and other material the drill had penetrated. In the course of this process, drilling “mud” was pumped down the pipe to lubricate the drill. Point the drill straight down, push the spinning drill pipe downwards until the end of it was near ground level, add another length of pipe to the drill string, and repeat. The well drilling I had witnessed, growing up in the Midwest, was a simple process. How was it possible to stick a drill into the ground and have it emerge again, perhaps half a mile away, at a precise location? How could they know where the drill was, once it was underground? And how could they change its direction if it strayed off course? How do you get the drill to go where you want? When I first heard of HDD, my curiosity was aroused. For the Dragonpipe, a final hole of around 30 inches will be needed for the larger of the two planned pipes (20 inches). Finally, the pipe itself is pulled through.
Horizontal directional drilling maximum distance series#
Then, the hole is enlarged by sending a larger drill or “auger” (or a series of them, in increasing sizes) through the hole. First, a relatively small pilot hole is drilled. I read up on HDD on the web, and this post summarizes what I’ve learned. It began at the first site, Judy Way in Aston, early in 2017. This drilling will be done at a dozen or more sites in the two counties.
Much of the Dragonpipe in Philadelphia’s suburban Delaware County and Chester County is to be built by drilling. It turns out that there is a technique called “horizontal directional drilling” (HDD) which is used for such situations. I was curious about how Sunoco/ETP was planning to deal with that. In rural most areas, that means digging a trench and laying the pipe four feet down.īut trenching is not practical in really built-up areas or under bodies of water like the many creeks in our area. The Dragonpipe (Mariner East 2) is to run entirely underground, with the exception of some pumps, valves, and vapor-control equipment.