Field Study on Jet Pump System in Horizontal Directional Drilling

Abstract:

As one method of Trenchless, HDD technology is widely used in new pipeline laying and existing pipeline repair in the fields of water supply and drainage, electric power, communications, oil and gas. The phenomenon of “overflow” is easy to occur when the HDD construction is carried out in the shallow stratum and the area where the stress of the overburden is small. This paper which combines the research status of "overflow" prevention and control technology domestic and foreign areas discusses the application of a new in-hole jet pump system design by a German company in trenchless engineering. The system sets a high-pressure jet pump system installed near the drill bit to collect cuttings formed during reaming process, thereby reducing the number of cuttings in the borehole space. The system is mainly composed of drill cuttings collection device, jet pump and connecting device, which can clean up about 98% of cuttings in the borehole. According to the needs of the project, four modes, such as borehole clearing, soft ground reaming & cleaning, combination and pipe pullback, can be used for pipeline laying. Field practice indicates that the longest drilling length can reach 122m per day associated with the system. At the same time, the existing problem is present in this paper. The screen will be blocked due to the formation of cuttings aggregation in complex formations with small diameter drilling. For the pipe pullback mode, how to change the return loop of cuttings is still the key problem to be solved in the jobsite.