Gazpromneft-Zapolyarye has commissioned its first “fishbone” well at an oil-rim deposit at the Chayandinskoye field in Yakutia. The initial flow rate from this multi-branched well has exceeded that of previously used horizontal structures, at about 400 tonnes per day.
This initial multi-branched “fishbone” well,* at an oil-rim deposit at the Chayandinskoye oil and gas condensate field (COGCF),** has a main shaft running to a length of 1.5 kilometres, with six lateral branches, each up to 830 metres long. Total borehole drilling exceeded 8.1 kilometres, of which 5.2 km was along productive strata (the “pay zone”). This construction has made it possible to increase coverage of the deposit, increasing the oil recovery factor (ORF). The initial flow rate through this fishbone well is more than 380 tonnes per day — double the level achieved through the standard horizontal wells previously used at Chayanda.
The Chayandinskoye field is marked by a complex geological structure and exceptionally low formation pressure. A 3D hydrodynamic model of the COGCF’s oil-rim deposit was used in creating the development programme for this asset. Specialists at Gazprom Neft’s Science and Technology Centre and Gazpromneft-Zapolyarye made approximately 500 multivariate calculations in comparing the advantages of various well types for producing Chayandinskoye oil before finally coming down in favour of a “fishbone” well.
A total 44 high-tech fishbone wells are to be drilled at the COGCF oil-rim deposit by end-2024, with five such multi-hole wells being commissioned this year. The company is currently operating seven oil-producing wells at the COGCF, and drilling several more.
Full-scale development of the COGCF oil-rim deposit will start in 2020. The CPF (which has a planned capacity of one million tonnes per year) is expected to be expanded and modernised by 2022. Gazpromneft-Zapolyarye is now building a
“The Chayandinskoye field is unique not just in terms of its reserves, but also in terms of the size and scale of the challenges we face here. Developing this oil-rim deposit — the reserves at which are classified as ‘hard-to-recover’ — is further complicated by the geological features present at Chayanda. The key to these deposits has proved to be cutting-edge drilling technologies and high-tech, intricately designed wells. These have already proved their effectiveness and, I am sure, will help us unlock the full potential of oil reserves at the COGCF — one of the largest fields in Eastern Siberia.”Vladimir Krupenikov Director General, Gazpromneft-Zapolyarye
* “Fishbone” well construction refers to a multilateral well running at a specific trajectory, with multiple offshoots running from the horizontal shaft — giving the well a “fishbone” shape. This construction significantly increases coverage of oil-saturated reservoirs in comparison with traditional horizontal wells, while requiring less extensive drilling meterage than would be involved in constructing a separate well for each horizontal shaft. A fishbone-trajectory well allows each branch to be directed at a specific oil-bearing section, without impacting neighbouring strata containing gas or water.
** The Chayandinskoye oil and gas condensate field is located in the Lensky District of the Republic of Sakha (Yakutia). The license to the field is owned by Gazprom PJSC. The field is unique in terms of its reserves, with recoverable reserves standing at 1.2 billion cubic meters of gas, and 61.6 million tonnes of oil. Gazpromneft-Zapolyarye LLC is developing the field’s oil reserves under a long-term risk agreement with Gazprom Dobycha Noyabrsk LLC, which is responsible for developing the gas element.