Sergey Doronin: “The use of geotechnical vessels for drilling stratigraphic wells is much cheaper than deployment of exploration drill rigs”
Russian geologists have gained their first experience in successful application of a relatively cheap method to conduct geological survey of the continental shelf subsoil by drilling stratigraphic wells of small depth using geotechnical vessels. That lets do without expensive exploration drill rigs but Russia has only one proper ship, head of RosGeo department for offshore geological exploration, told IAA PortNews.
- Could you please tell about the advantages of using geotechnical vessels as compared with exploration drill rigs when it comes to drilling of stratigraphic wells?
- Relative cheapness is the key advantage, of course. A well drilled from a geotechnical vessel is at least an order less compared to that drilled from an exploration drill rig. Of course, exploration rigs let drill deeper stratigraphic or parametric wells on the shelf, but that is not needed amid the current poor knowledge. The main idea of stratigraphic drilling is to base on geophysical data for determining areas with the needed layer coming close to the seabed and taking samples by relatively shallow drilling.
Notably, the number of exploratory drill rigs currently able to operate on our Arctic shelf is limited. Almost all the facilities are currently run by Gazprom: two semi-submersible drilling rigs "Polar Star" and "Northern Lights" as well as two jack-up drilling rigs "Arctic" and "Amazon". So, the number of available exploration drilling rigs is not that large today while organization of their operation requires numerous activities including engineering preparation of drilling sites, creation of coastal support bases and deployment of a fleet of auxiliary vessels. All that entails substantial financial and time investments in the case of using exploration drill rigs. However, our experience shows that excessive costs can be avoided without prejudice to the task.
- What is the key product of stratigraphic drilling?
- The purpose of a geological survey is to create a reliable geological model of studied region. The main source of information in offshore areas is a remote geophysical study but only core-drill sampling ensures defining of the layer properties. Therefore, the core is certainly the main product of stratigraphic drilling. Compared to exploratory drilling, where the main information is obtained by geo-physical well logging and the amount of core material is extremely limited, we always try to ensure continuous coring when making stratigraphic wells.
- How many geotechnical vessels able to conduct such works are available in Russia?
- Our drill ship Bavenit is now the best-equipped one on the shelf of the Russian Federation and, unfortunately, it is one of a kind today. The geotechnical vessel Trias homeported in the Far East features similar characteristics of drilling equipment, but it has only an anchor positioning system (holding at a point), which does not let it work in relatively deep waters.
Thus, the number of geotechnical vessels is even less than the number of exploration drill rigs, but far the market of stratigraphic drilling is still smaller. At the moment, our prime customer of such works is Rosneft. Besides, the first project initiated by the Federal Agency for Subsoil Use is being implemented this year, and Gazprom Neft is expressing keen interest in such works.
- Was this technology in use earlier?
- We have found no examples of such works in Russia before 2020. The very idea of using geotechnical vessels for drilling shallow stratigraphic wells belongs to Norwegian scientists and it was first implemented about forty years ago. Since our vessel Bavenit is a modification of another vessel that had proven itself well on the Norwegian shelf, it seems that the idea of organizing such work on our shelf is quite old but it has been implemented only recently.
In 2018-2019, geological exploration holding RosGeo held major overhaul of both the ship and its equipment. From 2020, we have been registering a decrease in demand for standard geotechnical works. In this situation, we had to look for activities and to expand the range of tasks so that we could maintain the vessel and develop in line with the market.
From 2020, we have been drilling stratigraphic wells ordered by Rosneft’s Arctic Research Center. It will be the third season this year. First, we studied the northern part of the Kara Sea, last year – the Laptev Sea with the works in the Chukchee Sea planned for this year.
From 2021, we have been successfully drilling pilot wells for Gazprom. It requires deeper wells without core sampling. The works are aimed at the site preparation for exploratory drilling. Such works are also very interesting and deserve a separate story.
- Is there any dependence on foreign ships in such works?
- To my personal memory, the recent geotechnical works involving foreign-flagged ships were conducted at the turn of 2014-2015 with no foreign contractors involved later. Before the Bavenit returned to the market, there were no dedicated ships with dynamic positioning. Being aware of that disadvantage the Holding made an investment decision on modernization of the ship (Bavenit- Ed.).
- What are the prospects of this activity amid sanctions in your opinion?
- In the current situation when we are concerned about the prospects of the offshore geological survey, we hope that our subsoil users will continue operating in the Arctic, we expect the government to join and to launch a large-scale programme on exploration of the Arctic shelf. That will make us more optimistic about the future and invest resources in phasing out of imports and modernization of our ships.