According to the literature and our own experimental data, the known types of residual oils, methods for determining the predominant type of residual oils for the oil reservoir targeted stimulation in order to increase oil recovery are considered. The qualitative characteristics of the properties of residual oils, by which it is possible to assess their changes by modern technical means are revealed. At residual oils additional displacement from the water-flooded reservoir, the phase state of the reservoir fluids, due to the redistribution of components between two reservoir fluids (reservoir water and residual oil), as well as a change in the phase state depending on the saturation of the oil - solid phase and wax precipitation in reservoir conditions - play an important role. Examples of studying at a particular field not only the composition of the residual oil, but also the degree of development of reservoir reserves under conditions of its washing with fresh water, when oil wells geophysical prospecting can't provide reliable information about the oil saturation of different intervals of the reservoir in the flooded area, are given. The change in the phase state (wax precipitation in reservoir conditions) of surface samples and degassed deep oil samples taken from the same oil well in different years are given. It is recommended for the analysis of changes in the properties of reservoir fluids to create an operational data bank with a data monitoring function, the ability to build maps and histograms of the distribution of physical and chemical properties both along the strike and along the depth of the beds.
The obtained on the basis of areal and temporary monitoring information on changes in the properties of reservoir fluids allows to identify the oil reservoir zones with varying degrees of oil saturation and assess the quality of residual oils, which makes it possible to monitor the state of the developed deposit and adopt optimal management decisions.
1. Surguchev M.L., Gorbunov A.T., Zabrodin D.P. et al., Metody izvlecheniya ostatochnoy nefti (Residual oil recovery methods), Moscow: Nedra Publ., 1991, 347 p.
2. Ashmyan K.D., Vol'pin S.G., Kovaleva O.V., To the question about the development of stranded (In Russ.), Trudy NIISI RAN, 2019, V. 1, pp. 23–28.
3. Kovalev A.G., Kovaleva O.V., Kozlov G.A., Maslov S.A., Prospects for the isolation of commercial reservoirs with in-circuit flooding according to core analysis (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 1989, no. 10, pp. 78–79.
4. Namiot A.Yu., Rastvorimost' gazov v vode (Solubility of gases in water), Moscow: Nedra Publ., 1991, 167 p.
5. Nafikov A.A., Khisametdinov M.R., Fedorov A.V. et al., Changes in composition and properties of crude oil resulting from application of enhanced oil recovery technologies (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2017, no. 9, pp. 100–103.
6. Titov V.I., Zhdanov S.A., Changes in the composition of reservoir oils in the development of fields (Overview) (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 1988, no. 8, pp. 26–28.
7. Kovaleva O.V., Sostav i svoystva ostatochnoy nefti v obvodnennykh zonakh produktivnykh plastov (Composition and properties of residual oil in watered areas of productive formations): thesis of candidate of technical science, Moscow, 1988.
8. Kovaleva O.V., Vliyanie razlichnykh faktorov na izmenenie sostava ostatochnoy nefti (The influence of various factors on the change in the composition of the residual oil), Collected papers “Nauchno-tekhnicheskie problemy razrabotki i obustroystva neftyanykh mestorozhdeniy” (Scientific and technical problems of oil fields development and field facilities), Proceedings of Giprovostokneft', 1990, pp. 103–114.
9. Kovaleva O.V., Ob izmenenii svoystv ostatochnoy nefti v protsesse razrabotki mestorozhdeniy metodom zavodneniya (Changes in the properties of residual oil in the process of field development by water flooding), Proceedings of All-Union Conference on Oil Chemistry, Tomsk, 1988, pp. 138–139.
10. Blyumentsev A.M., Kononenko I., Operativnyy monitoring razrabotki neftyanykh mestorozhdeniy na pozdney stadii s tsel'yu povysheniya izvlecheniya nefti (Operational monitoring of the development of oil fields at a late stage in order to increase oil recovery), Proceedings of International Scientific and Practical Conference, Kazan': FEN Publ., 2013, 408 p.
11. Eksperimental'nye metody issledovaniya parafinistykh neftey (Experimental methods for the study of paraffin oils): edited by Ashmyan K.D., Moscow: Publ. of VNIIneft', 2004, 108 p.
12. Namiot A.Yu., Fazovye ravnovesiya v dobyche nefti (Phase equilibria in oil production), Moscow: Nedra Publ., 1976, 180p.
13. Ashmyan K.D., Vliyanie mineralizatsii vody na vzaimnuyu rastvorimost' vody i komponentov plastovykh neftey v usloviyakh neftyanykh zalezhey na bol'shikh glubinakh (The effect of water salinity on the mutual solubility of water and components of reservoir oils in the conditions of oil deposits at great depths): thesis of candidate of technical science, Moscow, 1985.
14. Ashmyan K.D., Kovaleva O.V., Nikitina I.N., Method for evaluating the paraffin phase state in raw oil (In Russ.), Vestnik TsKR Rosnedra, 2011, no. 6, pp. 11–14.