Almost 70 years ago, academician A.P. Krylov proposed a binomial formula for calculating oil recovery factor (ORF), which is still used in the design of oil field development. The article presents the definitions of the coefficients included in the binomial and three-term formulas for calculating ORF, their physical meaning in the works of famous scientists has differences. Currently, the design of the development of oil fields is carried out on the basis of three-dimensional hydrodynamic models. The volumetric sweep efficiency included in the binomial ORF calculation formula is calculated in the reverse way based on the known value of the displacement efficiency obtained in laboratory conditions and the ORF value calculated based on solving the direct problem of three-dimensional reservoir simulation. The article shows that the volumetric sweep efficiency is equal to the coefficient of utilization of mobile oil reserves and represents the proportion of reserves recovered by the end of development or by the current point in time when determining the current ORF, of all mobile oil reserves contained at the oil field. Unlike the flooding coefficient in the three-part formula for calculating ORF, which shows the proportion of recoverable reserves from mobile reserves covered by displacement processes, the volumetric sweep efficiency or utilization factor of mobile oil reserves in the binomial formula characterizes the proportion of recovered reserves from all mobile reserves covered by the development. The presented interpretation of the physical value of the volumetric sweep efficiency makes it possible to calculate its distribution in a direct way based on a three-dimensional hydrodynamic model at any given time representing accumulated oil production by changing the oil saturation of the model cells.
References
1. Krylov A.P., Sostoyanie teoreticheskikh rabot po proektirovaniyu razrabotki neftyanykh mestorozhdeniy i zadachi po uluchsheniyu etikh rabot (The state of theoretical work on the design of oil fields and the tasks to improve these works), Collected papers “Opyt razrabotki neftyanykh mestorozhdeniy i zadachi po uluchsheniyu etikh rabot” (Experience in the development of oil fields and tasks to improve these works), Moscow: Gostoptekhizdast Publ., 1957, pp. 116–139.
2. Borisov Yu.P., Ryabinina Z.K., Voinov V.V., Osobennosti proektirovaniya razrabotki neftyanykh mestorozhdeniy s uchetom ikh neodnorodnosti (Features of designing the development of oil fields, taking into account their heterogeneity), Moscow: Nedra Publ., 1976, 286 p.
3. RD 153-39.0-110-01. Metodicheskie ukazaniya po geologo-promyslovomu analizu razrabotki neftyanykh i gazoneftyanykh mestorozhdeniy (Methodical instructions on geological and field analysis of oil and gas fields development), Moscow: Publ. of Ekspertneftegaz, 2002, 119 p.
4. Amelin I.D., Bad’yanov V.A., Vendel’shteyn B.Yu. et al., Podschet zapasov nefti, gaza, kondensata i soderzhashchikhsya v nikh komponentov (Calculation of reserves of oil, gas, condensate and their components): edited by Stasenkov V.V., Gutman I.S., Moscow: Nedra Publ., 1989, 270 p.
5. Lysenko V.D., Grayfer V.I., Ratsional’naya razrabotka neftyanykh mestorozhdeniy (Rational development of oil fields), Moscow: Nedra Publ., 2005, 605 p.
6. Zheltov Yu.P., Razrabotka neftyanykh mestorozhdeniy (Oil field development), Moscow: Nedra Publ., 1986, 332 p.
7. OST 39-195-86, Neft’. Metod opredeleniya koeffitsienta vytesneniya nefti vodoy v laboratornykh usloviyakh (Oil. The method of determining the coefficient of oil displacement by water in the laboratory).
