A study of the state of residual oil and mobile water in the process of oil displacement by water from core samples was carried out. The structure of residual oil at the micro level was studied. Analysis of available experimental approaches to the study of residual oil in core samples has shown that existing methods do not provide information on the structure of residual oil saturation. There are no reliable ways to study the structure of residual oil and the relationships of residual oil with the microstructure of the pore space. To solve the problems of structuring residual oil, it is proposed to use an innovative technology of diffusion-relaxation spectroscopy of nuclear magnetic resonance (2D NMR). Diffusion-relaxation two-dimensional spectroscopy uses differences in the values of the diffusion coefficients of oil and water. Relaxation spectra are used to distinguish oil from water. The analysis of the microdistribution of oil and water is carried out regardless of the viscosity of the oil. 2D NMR spectroscopy allows to study microscopic state of residual oil in an undisturbed core. The data can serve as a basis for creating effective methods for enhanced oil recovery. The principles of measurement and interpretation of 2D NMR spectra are described. With the help of the proposed methodology, a core study of the Shengli deposit (China) was carried out. The oil of this field has a high viscosity, and standard NMR technologies do not allow obtaining high-quality results. Using the proposed innovative technology, two-dimensional spectra for different stages of flooding were obtained and the state of residual oil at different stages was determined. The research results demonstrate a stable relationship between the NMR parameters of residual oil with the structure of the pore space and wettability. Differentiation of the mechanisms of formation of residual oil and its structure under the dominance of hydrodynamic and interphase forces is carried out. The role of the mobility of injected and residual water in the formation of residual oil is investigated.
References
1. Mikhaylov N.N., Ostatochnoe neftenasyshchenie razrabatyvaemykh plastov (Residual oil saturation of developed reservoirs), Moscow: Nedra Publ., 1992, 240 p.
2. Mikhaylov N.N., Petrophysical support for novel technologies for the re-extraction of residual oil from man-modified pools (In Russ.), Karotazhnik, 2011, no. 7(205), pp. 126–137.
3. Petrova L.M., Foss T.R., Abbakumova N.A., Romanov G.V., Regularities of formation of the composition of residual oils (In Russ.), Georesursy = Georesources, 2007, no. 3(22), pp. 43–45.
4. Dinariev O.Yu., Abashkin V.V., Evseev N.V. et al., Digital core analysis in problems of designing the development of oil and gas fields (In Russ.), Neftegaz.RU, 2021, no. 5(113), pp. 50–58.
5. Savitskiy Ya.V., Current features of x-ray tomography in examination of core samples from oil and gas deposits (In Russ.), Vestnik Permskogo natsional’nogo issledovatel’skogo politekhnicheskogo universiteta. Geologiya. Neftegazovoe i gornoe delo = Perm Journal of Petroleum and Mining Engineering, 2015, V. 14, no. 15, pp. 28–37, DOI: http://doi.org/10.15593/2224-9923/2015.15.4
6. Prusov E.S., Computed tomography for tasks of 3D materials science (In Russ.), Fundamental’nye issledovaniya, 2015, no. 5–2, pp. 318–323.
7. Emel’yanycheva E.A., Abdullin A.I., Study of petroleum modified bitumens using atomic force microscopy (In Russ.), Vestnik Kazanskogo tekhnologicheskogo universiteta, 2012, V. 15, no. 12, pp. 172–174.
8. Rudenko M.F., Surkov M.I., Nadirov N.K., Studies in fluorescence analysis of oil products (In Russ.), Vestnik Astrakhanskogo gosudarstvennogo tekhnicheskogo universiteta, 2008, no. 6(47), pp. 153–157.
9. Tugarova M.A., Balmasov E.L., Nesterov A.R., Petrova V.I., Application of confocal fluorescence microscopy in the examination of oil-and-gas bearing sedimentary rocks (In Russ.) Neftegazovaya geologiya. Teoriya i praktika, 2012, no. 1, pp. 1–20.
10. Zielinski L., Ramamoorthy R., Minh C.C. et al., Restricted diffusion effects in saturation estimates from 2D diffusion-relaxation NMR maps, SPE-134841-MS, 2010, DOI: http://doi.org/10.2118/134841-MS
11. Skvortsov B.V., Skvortsov D.B., Malysheva-Stroykova A.N., Theoretical bases of complex measurements of indicators of quality of oil products the method of the nuclear magnetic resonance (In Russ.), Izvestiya Samarskogo nauchnogo tsentra Rossiyskoy akademii nauk, 2011, V. 13, no. 6, pp. 252–258.
12. Toumelin E., Torres-Verdín S., Sun V., Keh-Jim D., Limits of 2D NMR interpretation techniques to quantify pore size, wettability, and fluid type: A numerical sensitivity study, SPE-90539-PA, 2006, DOI: http://doi.org/10.2118/90539-PA
13. Mikhaylov N.N., Motorova K.A., Sechina L.S., Geological factors of wettability of oil and gas reservoir rocks (In Russ.), Neftegaz.RU, 2016, no. 3(51), pp. 80–90.
