Facies model of V13 formation (Vendian, Nepa suite) and its use for geological exploration

UDK: 550.834.017
DOI: 10.24887/0028-2448-2021-3-14-20
Key words: facies model, Nepa suit, Vendian, Eastern Siberia, fluvial fan, seismic 3D, well logs, core
Authors: V.S. Vorobev (Gazpromneft NTC, LLC, RF, Saint-Petersburg), R.R. Khustitdinov (Gazpromneft NTC, LLC, RF, Saint-Petersburg), K.V. Zverev (Gazpromneft NTC, LLC, RF, Saint-Petersburg), N.A. Ivanova (Siberian Research Institute of Geology, Geophysics and Mineral Resources JSC, RF, Novosibirsk), D.V. Khipeli (Schlumberger Logelco Inc., RF, Moscow), L.N. Shakirzyanov (Gazpromneft-GEO LLC, RF, Saint-Petersburg)

The high facies variability of V13 formation (Nepa suit) determines the reservoir properties anisotropy and the difficulty to identify promising areas for exploration and production drilling. As a result of core studies, processing and interpretation of 3D seismic survey, the detailed seismic facies model was built. Its application made possible to increase the degree of models verifiability from 15 to 85% and to optimize the number of exploration wells need to drill and to base an objective project business case. The best reservoirs were formed in the lower part of the formation, they are represented by facies of sandy fan and distribution channels, confidently identified using modern 3D seismic survey; the width of the fluvial cones ranges from 5–7 to 10–18 km, and the length from 5–8 to 20 km. According to the core, well logging and seismic data, a regular decrease in net pay to the edges of the cones is observed, and the proportion of the clay fraction increases. Uncertainty in the assessment of the vertical and lateral anisotropy of the reservoir is used for alternative concepts in 3D geological and hydrodynamic models. Developed methods and approaches, conceptual models, and the results obtained (sizes of facies bodies, their connectivity and reservoir properties) are can be used for analogous fields in the region in order to create a reliable predictive basis for drilling and production forecasting.

References

1. Vorob'ev V.S., Chekanov I.V., Klinovaya Ya.S., The distribution model of terrigenous reservoirs and saline sand-gravelite deposits within the fields of the central part of the Nepal arch (In Russ.), Geologiya nefti i gaza, 2017, no. 3, pp. 47–60.

2. Miall A.D., The geology of fluvial deposits: sedimentary facies, basin analysis and petroleum geology, Springer-Verlag Berlin Heidelberg, 2006, p. 503.

3. Saez A., Anadon P., Herrero M.J., Moscariello A., Variable style of transition between Palaeogene fluvial fan and lacustrine systems, southern Pyrenean foreland, NE Spain, Sedimentology, 2007, V. 54, pp. 367–390.

4. Hampton B.A., Horton B.K., Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia, Sedimentology, 2007, V. 54, pp.  1121–1147.

5. Owen A., Nichols G.J., Hartley A.J. et al., Quantification of a distributive fluvial system: the salt wash dfs of the morrison formation, SW U.S.A., Journal of Sedimentary Research, 2015, V. 85, pp. 544–561.

6. Nichols G.J., Fisher J.A., Processes, facies and architecture of fluvial distributary system deposits, Sedimentary Geology, 2007, V. 195, pp. 75–90.

The high facies variability of V13 formation (Nepa suit) determines the reservoir properties anisotropy and the difficulty to identify promising areas for exploration and production drilling. As a result of core studies, processing and interpretation of 3D seismic survey, the detailed seismic facies model was built. Its application made possible to increase the degree of models verifiability from 15 to 85% and to optimize the number of exploration wells need to drill and to base an objective project business case. The best reservoirs were formed in the lower part of the formation, they are represented by facies of sandy fan and distribution channels, confidently identified using modern 3D seismic survey; the width of the fluvial cones ranges from 5–7 to 10–18 km, and the length from 5–8 to 20 km. According to the core, well logging and seismic data, a regular decrease in net pay to the edges of the cones is observed, and the proportion of the clay fraction increases. Uncertainty in the assessment of the vertical and lateral anisotropy of the reservoir is used for alternative concepts in 3D geological and hydrodynamic models. Developed methods and approaches, conceptual models, and the results obtained (sizes of facies bodies, their connectivity and reservoir properties) are can be used for analogous fields in the region in order to create a reliable predictive basis for drilling and production forecasting.

References

1. Vorob'ev V.S., Chekanov I.V., Klinovaya Ya.S., The distribution model of terrigenous reservoirs and saline sand-gravelite deposits within the fields of the central part of the Nepal arch (In Russ.), Geologiya nefti i gaza, 2017, no. 3, pp. 47–60.

2. Miall A.D., The geology of fluvial deposits: sedimentary facies, basin analysis and petroleum geology, Springer-Verlag Berlin Heidelberg, 2006, p. 503.

3. Saez A., Anadon P., Herrero M.J., Moscariello A., Variable style of transition between Palaeogene fluvial fan and lacustrine systems, southern Pyrenean foreland, NE Spain, Sedimentology, 2007, V. 54, pp. 367–390.

4. Hampton B.A., Horton B.K., Sheetflow fluvial processes in a rapidly subsiding basin, Altiplano plateau, Bolivia, Sedimentology, 2007, V. 54, pp.  1121–1147.

5. Owen A., Nichols G.J., Hartley A.J. et al., Quantification of a distributive fluvial system: the salt wash dfs of the morrison formation, SW U.S.A., Journal of Sedimentary Research, 2015, V. 85, pp. 544–561.

6. Nichols G.J., Fisher J.A., Processes, facies and architecture of fluvial distributary system deposits, Sedimentary Geology, 2007, V. 195, pp. 75–90.



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