【Ten Years of Rapid Development in Chemical Engineering Equipment】China’s First Trench Directional Drilling Project from 1973 to 2018

The directional drilling crossing project in the Hulushan Bay Trench is a key project for the Wafangdian-Changxingdao natural gas branch pipeline project. Since this trench forms the necessary route for the entire Wachang Line pipeline, the success of the directional drilling passage is the foundation for the construction of the entire line. The directional drilling project for the Hulu Mountain Bay Trench is a trench crossing project from land to island, with a crossing length of 833.8 m and a pipe diameter of 355.6×7.1 mm. The main geological formations encountered include medium-weathered quartz sandstone and red clay; there is a transition between hard and soft rock types, the rocks are highly fractured, and their uniaxial compressive strength is high. These characteristics render the construction technically challenging and carry high risks. Moreover, the angle of penetration and excavation is large, and the angle between the pre-fabricated pipeline and the penetration axis is significant, which poses great difficulties for pulling the pipeline back after penetration.

The strata in the Hulushan Bay Trench crossing area are complex, making the construction process challenging. During drilling, there is a significant difference in hardness between the various strata, with clear boundaries between hard and soft layers; moreover, the rocks are quite fractured, which makes it easy for mud to leak during drilling. During drilling operations, it is necessary to continuously adjust the mud pressure and viscosity based on changes in the stratum, in order to minimize the leakage of mud along fractures and to facilitate a smooth transition between soft and hard strata, thereby effectively reducing construction risks. During the pulling-back phase, there are issues such as a large angle between the crossing axis and the prefabricated pipelines, numerous bends in the prefabricated pipelines, and large spans for these pipelines. The prefabricated pipeline work area features multiple deep trenches; the deepest one is 12 meters deep and 105 meters long, posing significant difficulties for pulling the pipelines back. Additionally, the pre-fabricated pipeline makes a 31-degree turn with the alignment axis 50 meters after the excavation point, and another 36-degree reverse turn 150 meters after that, which has a serious impact on the pulling back of the pipeline. Before pulling back, a scaffold is erected using deep ditches; then roller frames are placed to allow smooth crossing over the obstacles posed by these ditches. At corners, trenches are dug to ensure that the pipelines being pulled back are subjected to even stress and can transition through the corners smoothly.

At 17:00 on August 19, after overcoming numerous challenges, the winding pre-retraction pipeline was guided along the designed route into the carefully drilled hole; after 8 hours of retraction, it was successfully retracted in one go. During the project construction, all the personnel involved showed perseverance, a willingness to take responsibility, and the ability to overcome numerous difficulties. With a spirit of tenacious effort and a positive attitude, they dedicated themselves to the construction of the directional drilling project in the Hulushan Bay Trench, and ultimately achieved successful one-time pull-through of the pipeline. This removed the biggest obstacle to the Wachang Pipeline Project, ensuring that the entire pipeline could be put into operation on schedule. Their efforts were highly praised and recognized by the client, PMC, supervisors, and EPC contractor! At the same time, it established a positive brand image for Pipeline Company No. 4 and demonstrated its first-class construction capabilities.

The first directional drilling project across a sea trench in China – the directional drilling project for the Wafangdian-Changxingdao natural gas branch pipeline through the Hulushan Bay sea trench – has been successfully completed, providing a solid guarantee for the timely commissioning of the Wafangdian-Changxingdao pipeline project. To the pride of the people of Cangzhou, the key drilling pipes used in the project construction were products manufactured by our city’s Bohai Nengke Drilling Pipes Company. 　　The directional drilling project through the Hulushan Bay Trench is of great significance as it relates to the construction of the entire Wachang pipeline project. At the same time, this project is another trench crossing from land to island, the first of its kind in China; the crossing length is 833.8 meters, with a pipe diameter of 355.6×7.1 millimeters. To ensure the successful completion of the project, the contractor, CNPC Pipeline Bureau, carefully selected high-quality penetration drill pipes produced by Bohai Nengke. 　　Bohai Nengke Drilling Rod Company is a specialized enterprise in our city that manufactures high-strength drilling rods for oil exploration and pipeline crossing. In recent years, CNPC Pipeline Bureau has used the Bohai Nengke series of penetration drill pipes in various key pipeline penetration projects across the country, setting the world record for directional drilling penetration on eight consecutive occasions. Related products have also made a remarkable appearance in the overseas markets under the Belt and Road Initiative; they successfully overcame the challenge of a 2,040-meter directional drilling operation that lasted 8 months, setting two records: the first time that directional drilling technology was used in Pakistan to cross the Indus River, and the longest distance ever covered using pipes with a diameter of 42 inches. What was used this time were high-strength, high-torsion-resistant, and high-toughness drill pipes of a high-grade type, innovatively developed by Bohai Nengke. Their tensile and torsional strength is 1.3 times that of ordinary drill pipes of the same specification, granting them excellent comprehensive mechanical properties – making them particularly suitable for penetration projects involving extremely high torque and force. 　　The completion of China’s first directional drilling project across a oceanic trench was a resounding success. The drilling rods used in the Bohai Nengke project managed to overcome various challenges, including the complex stratigraphic structure of the operation area, a large angle required for penetration, and a significant angle between the pre-made pipelines and the drilling axis, thereby further enhancing the appeal of \"Cangzhou Manufacturing\".

【Ten Years of Rapid Development in Chemical Engineering Equipment】The First Domestic Sea-to-Sea Directional Drilling for Oil and Gas Pipelines from 1973 to 2022 https://bbs.hcbbs.com/thread-3587766-1-1.html (Source: Haichuan Network – Chemical Industry Trends)