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Home / Issue Archive / 2011 / September #9 / SP VIS-MOS Expands the Boundaries of Horizontal Directional Drilling (HDD)

№ 9 (September 2011)

SP VIS-MOS Expands the Boundaries of Horizontal Directional Drilling (HDD)

   The underwater segment of the project entitled “The Inter-settlement Gas Pipeline From Vladivostok Gas Distributing Station to Natural Gas Consumers of Russkiy Island with a Branch to TEC-2 Power Station, Vladivostok, the Primorye Territory” was completed on 16 August 2011, in preparation for APEC-2012.

By This article was supplied courtesy of SP VIS-MOS Company

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   Natural gas will come from the Sakhalin – Khabarovsk – Vladivostok trunk pipeline and will be used as the main fuel for the TEC-2 power station and for heating the facilities of the summit.

   The gas pipeline passes under Bospor – Vostochnyi Strait; the project operator has chosen horizontal directional drilling (HDD) technology as a method that will not impede with navigation and will keep the ecosystem intact.

   This is a unique project – this underwater pipeline is unprecedented not only in length but in other parameters, too. Its length is 2,857 meters for the main thread and 2,773 meters on the reserve line. The depth of the pipeline is 30 meters below the deepest sea point. The diameter of the protector – 426 mm, diameter of the service line – 273 mm. Elevation difference from the entry point to the bottom of the borehole is 140 meters on the mainland side and 100 meters on the Russkiy Island side.

   SP VIS-MOS company participated in this project as HDD subcontractor. Gazpromregiongaz was the Ordering Party, Spetsgazremstroi – the prime contractor, IPSK NGS-TEMPOBUR – contractor for project design.

   Engineering staff of the company, realizing the strategic importance of the pipeline for the development of the Primorye Territory, on the one hand, and recognizing the uniqueness and complexity of the object, on the other hand, paid great attention during the preparatory period to project technology selection.

   It was decided to drill simultaneously two pilot boreholes from opposite directions for meeting halfway to form a single link. One drilling rig, (a PD-450/150 AM) was located on the mainland by Nazimova Cape, the other (a PD-220/67) – on Russkiy Island. The boreholes met 1,800 meters from the mainland and 1,050 meters from the Russkiy Island.

   To keep right on the drilling route and complete the linkage with the required accuracy, the company used one of the most up-to-date navigation systems, which uses a computer software to enable the drill bits to literally “see” each other.

   For this project SP VIS-MOS acquired drilling tools for heavy-duty soils from the world’s best manufacturers. But the pilot drilling revealed that although the geologic data was quite accurate, it failed to give a precise picture of soil abrasion and fracturing. With up to 174 MPa soil strength (equal to the strength of metal), abrasion was such that the cogs of tailor-made cone-rock bits were gone within mere 200-250 meters. This tool wear was impossible to foresee based on the geologic data provided.

   Consequently, during the course of the project the company had to turn to Australia to order exclusive drilling tools – diamond (PDC) bits. This equipment costs several times more than rock bits; the material costs were exacerbated by the time lag. Drill bits manufacture and complex customs and logistics procedures delayed the project, delaying the project completion date. Initially the company planned to install main and reserve lines one after another, but now, in order to cut down the delay, the work had to be run in parallel.
Diamond bits significantly streamlined and speeded up the drilling, but the bits themselves were gone within 400-500 meters. In world practice of directional drilling, no company had ever faced such tool losses.

   The selection of drilling muds was also complicated as the solution had to be prepared with salted water, using a special gel powder with additives to achieve the level of consistency sufficient for countering extensive fracturing throughout the borehole route in parallel to doing the usual “drilling mud” work.

   The pipeline was installed from the island to the mainland. Due to the great length of the pipeline, and therefore the string weight, the company decided at this stage to combine the HDD technology with pushing technology. The 450-ton drilling unit pulled the pipe string on the mainland, while the 500-ton pusher on Russkiy Island pushed the string into the borehole to lower the rig load and minimize the emergency levels. This engineering solution proved successful and pipeline was installed.

   The link under Bospor – Vostochnyi Strait is unique: while docking links and ultra-long links do exist, there are no examples of docking links almost 3 kilometers long and drilled in the environments where soil strength approaches that of metal.

   The success of this project was due to the fact that the SP VIS-MOS engineers switched on out-of-the-box thinking, deciding to use a synergy of several technologies rather than implementing them one by one. As a result, the customer received a unique linkage while HDD technology, thanks to SP VIS-MOS, not just moved one small step forward but made a leap into the future.

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