Development of Hard-to-Recover Reserves
The Company’s portfolio of assets with hard-to-recover reserves currently consists of more than 120 fields with over 4 bt of oil in recoverable reserves. Rosneft’s key assets of this type are RN-Yuganskneftegaz and Vostok Oil, with aggregate hard-to-recover reserves of over 2 bt of oil. They are followed by RN-Nyaganneftegaz, RN-Uvatneftegaz and Samaraneftegaz currently accounting for about 90% of the Company’s resource base in terms of hard-to-recover assets.
The Company consistently develops its hard-to-recover oil reserves. Oil production from deposits classified as hard-to-recover reserves under the applicable laws amounted to 19.7 mmt amid the restrictions under the new OPEC+ deal. The share of hard-to-recover reserves rose from 9.7% of the Company’s output in 2019 to 10.2% in 2020. In 2020, Rosneft increased the number of production wells at fields with hard-to-recover reserves by 20% year-on-year to over 4.8 thousand wells.
In improving its development technologies, the Company focuses on well stimulation at low-permeability formations, in particular using more sophisticated and longer horizontal wells with a higher number of hydraulic fracturing stages. In recent years, Rosneft has commissioned yearly an average of ~100 wells with horizontal sections of over 1 km, using multi-stage hydraulic fracturing, to tap into formations with hard-to-recover reserves. The use of longer horizontal wells and a higher number of hydraulic fracturing stages enables the Company to effectively develop previously unprofitable deposits. On top of that, in 2020, the following activities were carried out as part of projects to develop low-permeable reservoirs:
- more than 50 elements of development systems with horizontal injection wells were drilled;
- more than 100 wells were drilled using infill drilling under the standard development scheme;
- a development technique for low-permeability reservoirs was created with the use of horizontal wells drilled along the regional stress with cross fractures from hydraulic fracturing enabling to boost well productivity rate compared to the standard development scheme and mitigate risks of breaking waterflood-induced fractures;
- a technology of simultaneous isolated production and injection into horizontal wells drilled using multi-stage hydraulic fracturing techniques (MSHF HW) was developed;
In the coming years, the bulk of production from hard-to-recover reserves will be concentrated in the Western Siberian fields with low-permeability formations of the Tyumen suite and the Achimov deposits. Beyond 2020, though, oil production from hard-to-recover reserves will largely depend on elimination of geological and engineering uncertainties related to appraisal and the choice of best development solutions. To this end, the Company implements an exploration programme coupled with pilot projects set to develop low-permeability formations, the Bazhenov suite and high-viscosity oil deposits as part of the Target Innovative Projects. Target Innovative Projects seek to develop technologies to tackle silty sand deposits (structurally complicated undersaturated ultralow-permeability reservoirs), to bring Bazhenov and Domanic plays into production, to introduce thermal recovery methods fit for ultrahigh-viscosity oil fields in the Samara Region, and to develop high-viscosity oil reserves of the Pokurskaya suite formations in Western Siberia.
In 2020, the Company completed the following key initiatives as part of the Bazhen pilot development programme:
- drilled ten horizontal wells with ball-n-drop completion systems in the Salymsky and Priobsky licence areas;
- minimised problems in the process of drilling horizontal wells under abnormally high pressure and temperature conditions. All wells were drilled and completed without any problems;
- the horizontal sections of the drilled wells averaged 970 m long, with a horizontal section of about 1,400 m long drilled for the first time in the Bazhenov suite;
- carried out multi-stage hydraulic fracturing and launched eight wells. The proppant weight was on average 72 tonnes per stage;
- the average initial oil flow rate per stage for launched horizontal wells was 6.8 t per day against the planned rate of 6 t per day.
Multi-stage hydraulic fracturing and the exploration programme in the Bazhenov suite will continue in 2021.