【Ten Years of Rapid Development in Chemical Processing Equipment】737–2021: Subsea Directional Drilling for 1422-mm Long-Distance Pipelines
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Witnessing the decade-long rapid development of chemical processing equipment, we celebrate the prosperity and strength of modern China. Greater participation by everyone makes things even more exciting; with you here, Haichuan becomes even better. This is just a modest contribution to spark further discussion – we welcome everyone to engage more actively in forum exchanges and discussions; replies will be rewarded, and discussions are encouraged. ------------------------------------------------- At 1:58 a.m. on November 17, 2019, with the successful completion of the directional drilling operation for the Nachaoh River section of the Tangshan LNG transmission pipeline project, the Pipeline Bureau set a new record for underwater directional drilling of long-distance pipelines with the largest diameter of 1,422 millimeters in China. It is reported that the directional drilling for the Nachao River project covers a length of 1,289.93 meters. This is the first time in China that such a procedure has been carried out on large-diameter, high-pressure pipelines in marine sedimentary formations; the difficulties involved in this type of construction are rare worldwide. This project demonstrates the pipeline construction company’s strong capabilities and advanced technical skills in the field of directional drilling.
The Tangshan LNG export pipeline project starts at the reception station of the Tangshan LNG project in Hebei Province and ends at the Yongqing terminal station in Langfang City, Hebei Province. The Na Chao River directional drilling passage is located in the Caofeidian Industrial Zone of Tangshan City. It is a 1,000-meter-wide area that was created during the land reclamation efforts in Caofeidian; the sand taken for these reclamation projects formed what is known as a “river”. Nachao River is an artificial waterway that connects to the Bohai Bay. The pipeline design institute responsible for the design of this tunneling project took into account the lack of domestic experience in carrying out long-distance directional drilling of 1422-mm diameter pipelines; as a result, the designers conducted specialized technical research, ranging from using software for simulation and analysis to gathering data on similar projects abroad ； A great deal of research has been conducted on various crossing risks that may arise during construction, as well as on the development of corresponding countermeasures, thereby laying a solid and reliable foundation for the successful completion of directional drilling crossings.
The team responsible for the underwater passage under the Na Chao River is the project department for Bid 1 of the Tangshan LNG key project, affiliated with the Pipeline Bureau. According to project director Lei Zhangbin, the marine sedimentary geological conditions in the Na Chao River are quite complex; the passage route has to pass through 12 different strata, with significant variations in the properties of these strata, as well as a mixture of soft and hard materials, making it difficult to control the direction of the passage. Pipeline Company No. 4 assigned experienced steering engineers to work on this project, and by utilizing the world’s advanced P2 high-precision steering system, it ensured the accuracy of curve control, allowing the guide holes to be dug in accordance with the designed curves. Furthermore, due to the large pipe diameter, the final hole diameter of 1.8 meters also poses a significant challenge to the stability of hole formation in the stratum. In advance, the project team conducted over 20 mixing tests on the geological conditions of the Na Chao River in order to determine a scientific mud formula, continuing these tests until the results were consistently stable, which ensured the successful completion of the pull-back process during the crossing. This project took 61 days. The Tangshan LNG transmission pipeline project is one of the key routes for supplying clean energy to the Beijing-Tianjin-Hebei region; it will play an important role in improving the energy structure of the entire area and contributing to the coordinated development of Beijing, Tianjin, and Hebei.