I've been wanting to talk about "inadvertent returns" ever since I heard Frank Cannon (Baroid) explaining some of the challenges horizontal drillers face related to drilling fluids. "Drilling fluid under pressure, downhole will find the path of least resistance. Right? Now when, for what ever reason, it decides not to follow the bore hole path back to the surface, which we call "returns," we call that a "frac out." For some of you professor types, you might want to call it "inadvertent returns."
Frac outs, inadvertent returns what ever you call it, it's not good. First, if it is severe, you lose returns - the ability to remove cuttings and keep the hole clean. You don't make a successful bore when you lose returns. Second, depending on where drilling fluid decides to venture, you may be creating an environmental nightmare. Of special concern here are waterways and groundwater aquifers. A third concern is threat to subsurface integrity - under roads, rivers and enbankments. HDD has a well-deserved reputation for being non-intrusive and the least disruptive technique for installing cable, pipe and environmental remediation methodology. There is no guarantee with HDD, but the quicker inadvertent returns can be detected, the better.