Huayuan News
At 10:40 a.m. on February 21, 2014, Huayuan successfully completed the pipeline pullback for the Jingzhou–Shishou natural gas pipeline Yangtze River HDD crossing project, marking another successful crossing of the Yangtze River following the company’s earlier achievement on April 6, 2012, during the Huangda Pipeline Yangtze HDD project.
The project, located in Jingzhou City, Hubei Province, involved a total HDD crossing length of 1,837.44 meters, using a φ406.4 × 10.3 mm pipeline. The designed entry and exit angles were 20° and 19°, respectively, with a maximum depth of approximately 120 meters below the entry point.
The project posed significant challenges due to the presence of thick cobble and gravel strata at both ends of the crossing curve — nearly 300 meters in curve length and over 100 meters in vertical thickness at each end.
To reduce the traversed length through the cobble layers, Huayuan decided to increase the entry angle of the pilot bore and adopted a dual-rig simultaneous drilling approach, with both rigs drilling from opposite ends of the crossing at 20° and 19° angles. The pilot drilling operation used Huayuan’s independently developed docking guidance and positioning system** for precise underground alignment.
In less than a month, the two rigs completed the entire 1,837.44-meter pilot bore and achieved successful bit docking.
During the reaming phase, Huayuan tackled the common issue of borehole collapse in cobble layers by optimizing the drilling fluid formulation, enabling safe and efficient reaming of the pilot hole.
In terms of pipeline prefabrication, limited site space required the mainline pipe to be prefabricated in two sections, which were joined mid-process during pullback, increasing the overall project risk.
Additionally, due to the steep entry angle, the first 160 meters of pipeline had to be suspended in the air during pullback, with a maximum elevation of about 10.4 meters. Notably, 90 meters of the initial 176-meter section were positioned along a curved segment of the bore path.
This created an unprecedented challenge in Huayuan’s HDD history, setting a new company record for the highest suspended pullback segment, and the only instance where the suspended section was located along a curved trajectory.
