Professor Nikolay D. Nenkov was born in the town of Elena, Bulgaria in 1928. His academic career began at the Technical University of Sofia, from where he graduated in 1951, majoring in General Mechanical Engineering. Then, in 1959 he joined the Sofia University of Mining and Geology as a lecturer. Four years after defending his dissertation thesis on drilling mechanics in 1974, he was awarded the professorship of Drilling Machines and Mechanisms and Drilling Mechanics.
The creative path of Prof. Nenkov is reflected in more than 120 publications in various local and international drilling books and journals. He has written 5 books, 2 monographs. He has over 70 inventions, 26 of which are patented.
Prof. Nenkov has made outstanding contributions to the development of tools and equipment related to exploration drilling technology. He is the designer of several generations of retrievable drill bits and roller-latch assemblies, and he is among the world’s pioneers in these fields. For his outstanding scientific achievements, Professor Nenkov was awarded the Order of Cyril and Methodius (First Class) and was conferred the titles Honorary Inventor and Honorary Geo-Explorer by the Bulgarian government. In 1984, he was included in the bibliographic reference book Who’s Who in Science in Europe (published by Longman in the UK).
Prof. Nenkov has also held a number of public and administrative positions. He was vice dean and deputy rector of the Mining and Geological University of Sofia, and was also a member of the Bulgarian Attestation Committee.
Prof. Nenkov is still actively working and has been an important part of BG Drilling’s R&D team during the last few years.
Grigor Topev: Professor Nenkov, how did you start out at the Mining and Geology University of Sofia (MGU)?
Nikolay D. Nenkov: After graduating as a mechanical engineer in 1952 I worked in the construction department of the Bulgarian railways. After gaining experience in machine design, I was able to start work at Mashstroy (a large governmental department responsible for all the machine manufacturing in Bulgaria). I began with simple machine design jobs, but I was soon assigned to increasingly bigger tasks until, at last, I was assigned to the largest and most complicated projects. However, at this point I started feeling unwell and visited a doctor. He advised me that, for a young lad, my blood pressure was too high and I should leave my job. I was quite worried about my health and so I took his advice. Then, I heard about an open position at the Faculty of Mining Mechanics in the Mining and Geology University of Sofia, which I applied for successfully. Soon after, I was transferred to the drilling department where I started lecturing on drill-rig mechanics.
GT: How long you have been lecturing?
NDN: By the time I’d retired, I had been a lecturer of drill-rig mechanics for about 43 years.
GT: A large number of graduate drilling engineers find jobs in the industry quite easily. That is, when compared to other, more general subjects such as economics, law and business. Why is that?
NDN: First, the subject of drilling engineering is focused on the research and production of mineral resources and fossil fuels, while other subjects are of a more general nature. Secondly, the subject of drilling engineering is practical and provides useful knowledge of topics beyond the technology of drilling, such as of drills and equipment. When drilling, you reach different rock formations that in some cases require you to react quickly: you need to decide what to do, which equipment to use and how to use it. This profession requires creativity just as much as scientific aptitude.
GT: Where do drilling practice and theory meet?
NDN: They meet only at the drill site.
GT: Is it a mistake that most diamond drilling contractors do not currently invest in staff training? What would you advise them?
NDN: I think it is. The more automation we see on the drills the more this problem will deepen. Pressing buttons and moving levers is not enough. I would advise diamond drilling contractors to train their teams in the basics of drilling, so that the experience their staff is getting is based on some solid fundamentals, and not on personal science fictions. Without this approach, proper problem solving will not be possible and creativity will be absent.
GT: Why does the diamond drilling industry nowadays produce such a limited number of inventions? By contrast, we cannot say the same thing about surveying technologies.
NDN: During a Boart Longyear meeting in Amsterdam in the early summer of 1998 I presented 23 innovations, including a roller latch assembly, a retrievable drill bit and a bottom hole shock absorber. A good degree of interest was shown in these, but the prevailing opinion was that the current wireline system developed by Boart Longyear is so successful that the company doesn’t see any reason to invest in any such general innovations. So, actual market needs and innovation are not always travelling in the same direction.
GT: How did you end up at that meeting?
NDN: At that time, the Bulgarian governmental drilling department was buying a number of drilling tools from Boart Longyear for its exploration programs. The local representative was half Bulgarian, half Canadian and as he was familiar with my work he invited me to that meeting.
GT: What are the required qualities of a piece of equipment for it to be practical and to find commercial application?
NDN: Reliable, simple by design, easy-to-maintain and inexpensive.
GT: What is your favourite invention?
NDN: I enjoyed the work on the roller latch assembly. The existing form of latch assembly would easily get stuck, while with the rollers, retraction is guaranteed. I offered it to the Bulgarian geology committee in 1965, but they were reluctant. Despite that, the roller latch assembly was produced in Asenovgrad during the 70s in what was the biggest drilling manufacturing plant at that time, and the assembly was used in industry to a certain extent.
GT: Earlier in your career, you were involved with the Japanese company, Koken Boring Machine (one of Asia’s biggest drill rig manufacturers). Please tell us more about this.
NDN: During a conference in Algeria in 1987, I met with the president of Koken Boring Machine, Dr. Takumi Eguchi who expressed a keen interest in the retractable drill bit. Their representative visited Bulgaria a few months later and witnessed a demo run in Panagyurishte. Further cooperation was established, but no final commercial agreement was ever signed.
GT: Please tell us more about the work you did with the Swedish company, Hagby Bruk before it was acquired by Sandvik.
NDN: Hagby was interested in the retrievable drill bit and the bottom hole shock absorber, and we worked together in that direction for a period of three years. The shock absorber was manufactured and put into action with good results. Hagby has contributed to the diamond drilling industry with a variety of innovations and working with them was a genuine pleasure.
GT: I know you have a few developments that will be hard to find commercial applications for. Notwithstanding this, they remain very interesting. Could you please describe them?
NDN: Yes; first, there is the drill bit with flexible segments, designed to compensate rock foliation and reduce hole deviation. Secondly, there is the drill bit with replaceable diamond segments that reduce cost, and its modified version with segments that can be turned 180 deg and used a second time. A third one is the preloaded thread connection that increases the rod’s thread yield strength capacity; fourth is a thread-less centralizer or reaming shell that can slide and be locked onto any place on the drill string quickly and easily.
GT: Can you tell us about an interesting drilling case you have witnessed?
NDN: I remember some interesting fishing jobs. We experimented with a few special fishing tools, but I cannot recall any specific details, unfortunately.
GT: How were exploration works in Bulgaria managed before 1990?
NDN: The geology committee was the head of all exploration and drilling works, and underneath it were a few big drilling departments (in Sofia, Varna, Yambol, Asenovgrad and other) as well as a number of large departments for research, development and fabrication in Asenovgrad. These were large-scale campaigns for a relatively small country.
GT: What is the future of diamond drilling, in your opinion?
NDN: We will see more drill automation, which will reduce physical activity and increase safety. However, as I mentioned earlier, a thorough understanding of drilling processes – whether automated or not – is essential and without this, professionalism will be absent.
GT: What will we see the industry focusing more on?
NDN: Focus should be on deep-drilling techniques, as resources occurring at shallow depths have already been explored. Also, being able to reach multiple targets from one single hole will be the key to success.
GT: What is your advice to all drilling companies?
NDN: To focus on quality, not quantity.
GT: What is your advice to all drilling manufacturers?
NDN: I would advise them to create robust, low-cost and multifunctional equipment.
GT: What would you like to say to our readers?
NDN: Use all drilling equipment to its maximum capacity; use its hidden potential, as there is always such.
