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Multi-level lithological typization of rocks of the Bazhenov formation

UDK: 553.98.061.32
DOI: 10.24887/0028-2448-2019-8-13-17
Key words: Bazhenov formation, source formation, oil reservoirs, lithological typization of deposits, material composition, reservoir productivity, post-sedimentation transformations
Authors: V.D. Nemova (LUKOIL-Engineering LLC, RF, Moscow)

The Bazhenov formation is the main source formation in Western Siberia and contains oil-saturated reservoirs. The Bazhenov formation is promising for oil production, but at the same time it is extremely complex. The article proposes a multi-level lithological typization of sediments, developed o based on the study of more than 100 wells with the core of the Bazhenov formation within the Khanty-Mansiysk Autonomous District. Lithotypization contains 4 levels of detail. The first level includes two classes of rocks: carbonate-clay-carbon-siliceous (oil source rocks) and siliceous-carbonate (potential reservoirs). The rocks of the first class are oil source, contain liquid hydrocarbons in a sorbed state, which cannot be extracted using existing technologies. The rocks of the second class are also oil source, however, they often have reservoir properties, which is justified by a comparison of core studies with well and field studies to determine the intervals of inflow. The second level of litho typization contains seven groups of lithotypes, which are divided by the ratio of rock-forming components. Groups of lithotypes of the first class have their location in the section and differ in logging curves; it is extremely difficult to separate the groups of lithotypes of the second class according to the logging data and they can be found throughout the section. The third level of lithotypification consists of 11 lithotypes, distinguished by mineral composition, organic matter content, structural and texture features. The fundamental difference between this typification and the previous ones is the consideration of the texture features of the rocks, which allows you to immediately separate the source rocks and potential reservoirs. The fourth level of lithotypization is the mapping of the variety of rocks of the Bazhenov formation, where 33 subtypes of rocks are distinguished, which differ in mineral and biogenic inclusions, impurities, textures, and secondary transformations. Isolation of lithological subtypes of rocks with a characteristic set of faunal residues and impurities is necessary during detailed facies reconstructions. This classification allows the transition from studying rocks in transparent sections to building a three-dimensional geological model without losing a large amount of detailed lithological information. Confidently interpret the well data, compare geological sections of the suite according to core and GIS data with each other, determine the factors that control the productivity of the stratum, establish patterns of distribution of properties of potential reservoirs.

References

1. Korovina T.A., Zakonomernosti formirovaniya i rasprostraneniya kollektorov v bituminoznykh otlozheniyakh bazhenovskoy svity dlya otsenki perspektiv neftegazonosnosti zapadnogo sklona Surgutskogo svoda (Patterns of formation and distribution of reservoirs in the bituminous sediments of the Bazhenov formation to assess the oil and gas potential of the western slope of the Surgut arch): thesis of candidate of geological and mineralogical science, St. Petersburg, 2004.

2. Panchenko I.V., Nemova V.D., Smirnova M.E. et al., Stratification and detailed correlation of Bazhenov horizon in the central part of the Western Siberia according to lithological and paleontological core analysis and well logging (In Russ.), Geologiya nefti i gaza, 2016, no. 6, pp. 22–34.

3. Panchenko I.V., Razmyvy v bazhenovskikh otlozheniyakh Zapadnoy Sibiri: znachenie dlya korrelyatsiy razrezov i prognoza kollektorov (Scour in the Bazhenov sediments of Western Siberia: the value for the correlation of sections and reservoir forecast), Proceedings of 3rd EAGE/SPE scientific workshop “Nauka o slantsakh” (The science of shale), Moscow, 2019.

4. Alekseev A.D., Nemova V.D., Koloskov V.N., Gavrilov S.S., Lithological peculiarities of Lower Tutleimsky subsuite structure of Frolovsky oil-and-gas-bearing area in view of its oil potential (In Russ.), Geologiya nefti i gaza = The journal Oil and Gas Geology, 2009, no. 2, pp. 27-33.

The Bazhenov formation is the main source formation in Western Siberia and contains oil-saturated reservoirs. The Bazhenov formation is promising for oil production, but at the same time it is extremely complex. The article proposes a multi-level lithological typization of sediments, developed o based on the study of more than 100 wells with the core of the Bazhenov formation within the Khanty-Mansiysk Autonomous District. Lithotypization contains 4 levels of detail. The first level includes two classes of rocks: carbonate-clay-carbon-siliceous (oil source rocks) and siliceous-carbonate (potential reservoirs). The rocks of the first class are oil source, contain liquid hydrocarbons in a sorbed state, which cannot be extracted using existing technologies. The rocks of the second class are also oil source, however, they often have reservoir properties, which is justified by a comparison of core studies with well and field studies to determine the intervals of inflow. The second level of litho typization contains seven groups of lithotypes, which are divided by the ratio of rock-forming components. Groups of lithotypes of the first class have their location in the section and differ in logging curves; it is extremely difficult to separate the groups of lithotypes of the second class according to the logging data and they can be found throughout the section. The third level of lithotypification consists of 11 lithotypes, distinguished by mineral composition, organic matter content, structural and texture features. The fundamental difference between this typification and the previous ones is the consideration of the texture features of the rocks, which allows you to immediately separate the source rocks and potential reservoirs. The fourth level of lithotypization is the mapping of the variety of rocks of the Bazhenov formation, where 33 subtypes of rocks are distinguished, which differ in mineral and biogenic inclusions, impurities, textures, and secondary transformations. Isolation of lithological subtypes of rocks with a characteristic set of faunal residues and impurities is necessary during detailed facies reconstructions. This classification allows the transition from studying rocks in transparent sections to building a three-dimensional geological model without losing a large amount of detailed lithological information. Confidently interpret the well data, compare geological sections of the suite according to core and GIS data with each other, determine the factors that control the productivity of the stratum, establish patterns of distribution of properties of potential reservoirs.

References

1. Korovina T.A., Zakonomernosti formirovaniya i rasprostraneniya kollektorov v bituminoznykh otlozheniyakh bazhenovskoy svity dlya otsenki perspektiv neftegazonosnosti zapadnogo sklona Surgutskogo svoda (Patterns of formation and distribution of reservoirs in the bituminous sediments of the Bazhenov formation to assess the oil and gas potential of the western slope of the Surgut arch): thesis of candidate of geological and mineralogical science, St. Petersburg, 2004.

2. Panchenko I.V., Nemova V.D., Smirnova M.E. et al., Stratification and detailed correlation of Bazhenov horizon in the central part of the Western Siberia according to lithological and paleontological core analysis and well logging (In Russ.), Geologiya nefti i gaza, 2016, no. 6, pp. 22–34.

3. Panchenko I.V., Razmyvy v bazhenovskikh otlozheniyakh Zapadnoy Sibiri: znachenie dlya korrelyatsiy razrezov i prognoza kollektorov (Scour in the Bazhenov sediments of Western Siberia: the value for the correlation of sections and reservoir forecast), Proceedings of 3rd EAGE/SPE scientific workshop “Nauka o slantsakh” (The science of shale), Moscow, 2019.

4. Alekseev A.D., Nemova V.D., Koloskov V.N., Gavrilov S.S., Lithological peculiarities of Lower Tutleimsky subsuite structure of Frolovsky oil-and-gas-bearing area in view of its oil potential (In Russ.), Geologiya nefti i gaza = The journal Oil and Gas Geology, 2009, no. 2, pp. 27-33.



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