The rapid development of the Achimov drilling program on the Yamal Peninsula requires an increasing of the drilling efficiency and complicating the wells construction. These factors create new challenges. The pursuit of increasing the productivity of the production wells leads to an increase in the length of horizontal reservoir sections and the number of hydraulic fracturing stages. Since the beginning of the complicated horizontal wells’ drilling at the Urengoyskoye oil and gas field, the average length of the horizontal wellbores has increased from 1000 to 1500 m, and the number of hydraulic fracturing – from 3 to 7 stages.
Further extension of the horizontal well interval is associated with an increase in the bottomhole pressure and the risk of hydraulic fracturing. A pilot project for the horizontal wells’ construction in the Achimov deposits was launched at the Yamburgskoye field in 2019. Two such wells with the 1000 m horizontal interval were successfully drilled and completed. The results of the calculations and the obtained experience indicate a risk of the further horizontal interval increase. The implementation of managed pressure drilling (MPD) technology through the application of a low-density drilling mud and the precise control of the wellhead pressure can reduce the magnitude of repression during circulation and provide with an opportunity to drill longer intervals.
Applying MPD technology makes it possible to provide safe drilling operations, tripping, early kick detection and fluid losses, running and cementing liners. The next step in the Yamburgskoye field pilot project was the construction of a well with a 6500 m depth and the 2500 m horizontal interval in the Achimov strata. Calculations results demonstrated that with the application of conventional drilling technologies there is a high probability of hydraulic fracturing if the horizontal section is more than 1500 meters. In addition, to make possible more fracturing stages execution, the use of Plug & Perf technology is required, which demands the liner cementing. The liner cementing, in turn, is most likely impossible with the traditional approach. It was decided to drill an extended productive strata interval with the MPD technology application. It was required to optimize each element of the drilling system, including BHA, drilling muds, and drilling regimes to achieve the best results. The necessary regulations and procedures have also been developed which purpose was not only to provide more safety during drilling operations, but also to reduce the time of well construction.
MPD has become a new stage in the development of the Achimov program and made it possible to remove several geological restrictions. It also allowed to create conditions for the construction of more complex and efficient wells with a longer productive interval and many hydraulic fracturing stages. The experience obtained allows us to talk about the prospects of this solution for the construction of new wells in complicated geological conditions.
