CCT: Continuous Coring Tool from BG Drilling

February 16, 2024

BG Drilling launches its latest development to compete with Norwegian technology

by Kiril Apostolov, MSc, General Manager at BG Drilling Solutions

Fifteen years ago, leveraging their background from the industry leader Devico, Norway (now part of Imdex), the founders of BG Drilling, Associate Prof. Shteryo Lyomov, PhD and Grigor Topev, MSc set out to make a notable impact in the directional drilling field. Situated in Bulgaria—a country celebrated for its significant contributions to specialized R&D of in-the-hole tools during the socialist era—BG Drilling draws inspiration from a legacy of innovation. This heritage, tracing back to the seventies and eighties, includes Bulgarian achievements such as the development and patenting of the first directional coring tool, core barrel’s roller latch system, bottom-hole shock absorber, and retrievable core bit. Drawing on this rich tradition and expertise, BG Drilling has carved out its niche, quickly gaining recognition as a trusted partner in the mineral exploration industry, with its dedication to field service excellence acknowledged by clients and competitors. Its mission has been clear from the start: to deliver tools that not only enhance field operations but do so in a cost-effective manner. These guiding principles are embodied in the company’s culture and its flagship CWT range of tools.

‘For years, we have been avoiding direct competition with the coring technology, guided by what some might call old-fashioned ethics. However, with the industry evolving through acquisitions and the arrival of new competitors, the landscape has shifted. We’re now ready to showcase our full potential,’ shares Grigor Topev.

Building on the success of the CWT, BG Drilling Solutions is thrilled to present the Continuous Coring Tool (CCT) – the world’s first mechanically driven directional core drilling (DCD) system and, by operational principle, the second.

The Continuous Coring Tool is a drilling system designed to obtain core continuously while steering the hole. The core can be retrieved using an inner tube and overshot, just like with a regular wireline system. At the core of the CCT system lies the company’s CWT technology, with one of the main components being the acclaimed Roller Pad—a spring-operated mechanism that securely locks the stationary part of the tool, ensuring consistent directional control during drilling operations. By utilizing rollers to enhance grip, this innovative approach significantly reduces axial friction, markedly improving efficiency compared to other DCD systems.

CCT’s Roller Pad (patented)
CCT’s Roller Pad (patented)

The CCT is both effective and highly productive, averaging 15 to 20 m (49-66 ft) per shift. It is tailored for complex drilling plans, offering well-distributed deviations over long sections averaging 9° per 30 m (98 ft). An essential tool for projects with extensive and complex deviation requirements, it is capable of operating at depths of up to 3000 m (9843 ft). Versatile for both shallow and deep drilling, its applications range from precise hole navigation to branching, meeting the needs of core-critical projects in mineral exploration, geotechnical, and tunneling sectors.

The CCT is currently offered in N-size, boasting an industry-leading compactness at 4.5 m (14.77 ft) long and weighing 45 kg (99.2 lb), facilitating safer and more efficient use in restricted areas. It delivers a 3 m (9.84 ft) core of 32 mm (1.26 in) diameter per core run.

A new design of the CCT, aimed at enabling B-size coring, is currently under development, with a target launch date in 2025. Additionally, BG Drilling Solutions is preparing CCT’s versions to accommodate the other two principal sizes of drilling holes, B and H, enhancing the tool’s versatility and application across various drilling scenarios.

BG Drilling emphasizes on mechanically driven tools for their ability to navigate challenges that other systems might face. Deep drilling operations are associated with significant hydraulic losses or may experience hydraulic instability which can impact the efficiency of hydraulic-dependent tools. Systems like steerable bottom-hole motors which demand significant volumes of drilling fluid, can face operational challenges, such as stalling or reduced penetration at greater depths. Additionally, these systems necessitate extra mud pumps and smaller-sized drill rods, adding further complexity and potential drawbacks to their operation. Similarly, the reliability of packer grip and toolface locking in existing DCD systems might be compromised, leading to directional errors. By contrast, mechanically driven systems like the CWT and CCT operate independently from these limitations, showcasing consistent performance, particularly at depths below 2000 m (6562 ft), where their reliability and efficiency become even more pronounced.

Our focus has always been on R&D to supply the industry with state-of-the-art, cost-effective solutions. The mechanical tools are the pathway for major improvements in existing technology – they are rigid and reliable. Combined with other factors, they allow a substantial reduction of utilization expenses, nearly halving the service cost compared to the existing DCD systems.’ adds Associate Prof. Shteryo Lyomov.

CCT during its field trials
CCT during its field trials

Alongside the exciting launch of the CCT, BG Drilling is thrilled to unveil another groundbreaking patent-pending development: the modified CWT, called CWT Dual Mode (CWT DM). This advancement sets a new industry benchmark by introducing the first-ever capability for down-the-hole dogleg severity adjustments, an achievement unmatched by any other in the field. This innovation streamlines tripping operations, significantly elevating the CWT’s operational efficiency.

With the provision of three types of directional tools on the market, BG Drilling has introduced a classification system to help clients choose the most suitable tools for their projects. This system categorizes directional drilling jobs into three categories based on the deviation required per intervention, enhancing understanding of each tool’s functionality, and streamlining the selection process for particular drilling demands. This strategy enables informed decision-making, ensuring that tool choices are perfectly aligned with the specific requirements of drilling projects until the resumption of standard diamond coring operations.

Short-Range Deviations: Typically involving deviations of up to 5°, short-range deviations are crucial for keeping drilling operations on track. The CWT, with its ability to make precise, minor corrections, is perfectly suited for navigation of straight holes, offering an efficient and cost-effective solution compared to more complex tools like DCD systems. Wedges and similar tools also fall under this category.

Mid-Range Deviations: These corrections, ranging from 5 to 15°, often involve realigning trajectories that have significantly deviated from the planned path or executing close-proximity targets in branching jobs. The CWT DM’s versatility and its ability to adjust DLS without tripping make it an invaluable asset, balancing precision with the need for minimal intervention.

Long-Range Deviations: For deviations exceeding 15°, the challenge intensifies, requiring tools capable of handling complex steering and longer correction paths. This category demands sophisticated engineering and operational finesse, areas where BG Drilling’s CCT, downhole motors, or other DCD systems shine, ensuring successful navigation of even the most demanding deviations.

It’s important to note that short-range deviation tools like the CWT perform well across the other two categories, but their effectiveness may decrease due to the increased number of short interventions and thus increased tripping. Conversely, more complex tools are versatile across short and mid-range categories but come at a higher cost. The selection based on deviation categories does not apply when core retrieval is essential.

The CWT family
The CWT family

By offering a range of tools designed for specific deviation requirements, complemented by the exceptional on-site expertise of engineers with university degrees, BG Drilling secures a unique position in the drilling technology sector. As the company continues to innovate and refine its offerings, it is eagerly looking forward to presenting its latest achievements, including the CCT, at the upcoming PDAC in Toronto, Canada. Interested parties are invited to visit Booth 818 to explore the CCT and learn more about the company’s services. This event represents an excellent opportunity for BG Drilling to expand its impact, welcome new customers, and establish partnerships to bring its advanced solutions to new markets.

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