A petrographic study of the genesis of anomalous sections in the Bazhenov Formation, the Imilor deposit, Western Siberia

Research subject. Anomalous sections present in the oil- and bituminous-bearing Bazhenov Formation (BF), in the central areas of the West Siberian basin, are considered to have emerged due to the injection of plastic pulp masses from the sedimentation slope into weakly lithified basal deposits. The aim of this research was to evaluate the as-emerged rocks by analyzing their composition and structure at the macro- and micro- levels.
Materials and methods. We investigated reference well sections in the Imilor deposit to elucidate the interaction of the rocks with sandy-clay landslide pulp, their volumetric weight, ductility or brittleness, caused by the presence or absence of a continuous mineral frame.
Results. According to core and well logging data, nine regional packs were distinguished in the BF stratotype. The maximal depth of the natural hydraulic fracturing of the rocks is explained by their high bulk density. The lateral movement of the main slump mass is found to have occured on the stratigraphic level of the first and second BF packs, since these layers possessed zero-buoyancy with regard to the injected pulp under their approximate equality in terms of bulk density. The traces of such active movements were revealed in rock samples from the walls of horizontal cracks in the form of clay intrusions having a thickness of about 0.1 mm and strict orientation of all micro-crystals along the walls and the flow. It is shown that inclusions of the rocks under investigation (bazhenits) in BF are generally characterized by their initial stratigraphic sequence, which is confirmed by the sequential disintegration of proto-bazhenit plates during the process of BF up-floating on a growing sedimentation slope. During the disintegration of the lithified and non-lithified layers of radiolarits, the former crumbled due to alternating loads, while the latter - mobile radiolarites - were represented by the hydraulic fracturing liquid, along with quicksand.
Conclusion. A detailed petrographic study of core samples from intact deposits of the Bazhenov and George Formations and their anomalous sections have allowed their layer-by-layer comparison to be confirmed the landslide hypothesis and to be derived the information on the degree of lithification of the BF strata during the formation of its anomalous sections.

1. Borzenko E.I. (2009) Chislennoe modelirovanie techenii reologicheski slozhnoi zhidkosti v ploskikh kana lakh [Numeral modeling of tricky rheological fluid within plate slots]. Tomsk, Tomsk State Univ. Publ., 20 p. (In Russian)

2. Braduchan Ju.V., Bulynnikova S.P., Vyachkileva N.P., Gol’bert A.V., Gurari F.G., Zakharov V.A., Klimova I.G., Kozlova G.E., Lebedev A.I., Mesezhnikov M.S., Nal’nyaeva T.I., Turbina A.S. (1986) Bazhenovskii gorizont Zapadnoi Sibiri (stratigrafiya, paleogeografiya, ekosistema, neftegazonosnost’) [Bazhenov horizon of the West Siberia: stratigraphy, paleogeography, ecosystem, oil and gas productivity]. Novosibirsk, Nauka Publ., 216 p. (In Russian)

3. Deev E.V., Zol’nikov I.D., Staroverov V.N. (2012) Some types of deposits and textures as a result of rapid geological processes (on the example of different age complexes of northern Eurasian). Litosfera, (6), 14-36. (In Russian)

4. Eder V.G., Zamirailova A.G., Yan P.A. (2017) The regularities of the distribution of siliceous mudstones and “coccolith” member of the bazhenovformation. Geol. Geofiz., 58(3-4), 511-521. (In Russian)

5. Grishkevich V.F., Gatina N.N., Dolmatova S.V., Lagutina S.V., Laptei A.G., Mezhetskii V.V., Panina E.V. (2017б) Lithological markers of protobazhenit mats splitting on sedimentary slope. Litosfera, (4), 48-61. (In Russian)

6. Grishkevich V.F., Kasatkin V.E., Lagutina S.V., Moskalenko N.Yu., Smolyakov G.A., Panina E.V., Laptei A.G., Toropov E.S., Starikov V.S., Horoshev N.G., Blinkova A.V., Chernoskulova V.A. (2017в) Some aspects of Achimovo layers and abnormal sequences Bazhenovo Formation joint modeling. Geologiya, geofizika i razrabotka mestorozhdenii nefti i gaza, (9), 27-42. (In Russian)

7. Grishkevich V.F., Lagutina S.V., Panina E.V., Dolmatova S.S., Laptei A.G., Toropov E.S., Starikov V.S., Khoroshev N.G., Blinkova A.V. (2017a) Geomechanical model of bazhenov abnormal sequence’s generation: physical experiments and practical usage. Geologiya, geofizika i razrabotka mestorozhdenii nefti i gaza, (3), 33-47. (In Russian)

8. Malkin A.Ja. (2015) Rheology of suspenzion. Reologiya i fiziko-khimicheskaya mekhanika geterofaznykh system [Rheo logy and physic-chemical mechanics of heterophaze systems]. Moscow, Moscow St. Univ. Publ., 6-9. (In Russian)

9. Mikulenko K.I., Ostryi G.B. (1968) Slump formations in West Siberian Mesozoic deposits. Litol. Polezn. Iskop., (5), 11-118. (In Russian)

10. Nezhdanov A.A. (2004) Geologo-geofizicheskii analiz stroeniya neftegazonosnykh otlozhenii Zapadnoi Sibiri dlya tselei prognoza i kartirovaniya neantiklinal’nykh lovushek i zalezhei UV. Dis. … dokt. geol.-min. nauk [Geological and geophysical feature analyses of West Siberia oil productive sediments for non-anticline HC traps forecasting and mapping]. Doct. geol. and min. sci. diss., 458 p. (In Russian)

11. Osuji C.O., Weitz D.A. (2008) Highly anisotropic vorticity aligned structures in a shear thickening attractive colloidal system. Soft Matter. Advance Articles DOI: 10.1039/b716324j

12. Panchenko I.V., Nemova V.D. (2015) Bazhenov horizon detail reconstruction by lithological-paleontological marker’s definition. Nauchno-prakticheskaya konferentsiya “Puti realizatsii neftegazovogo i rudnogo potentsiala Hanty-Mansiiskogo Avtonomnogo Okruga–Yugry”. Vyp. XVIII, t. 1 [Ways of realization of oil and gas and ore potential of Khanty-Mansiisk Autonomous OkrugUgra. Proc. XVIII, vol. 1], 87-92. (In Russian)

13. Panchenko I.V., Nemova V.D., Smirnova M.E., Il’ina M.V., Baraboshkin E.JU., Il’in V.S. (2016) Stratigraphy and detail correlation of Bazhenov horizon in Western Siberia central part based on lithological and paleontological core studies. Geologiya nefti i gaza, (6), 22-34. (In Russian)

14. Wagner N.J., Brady J.F. (2009) Shear thickening in colloidal dispersions. Physics Today, American Institute of Physics, S-0031-9228-0910-010-8, 27-32.