Determination of parameters for texture-heterogeneous terrigenous reservoirs based on well logging data

UDK: 550.832
DOI: 10.24887/0028-2448-2017-10-86-89
Key words: texture heterogeneity, terrigenous reservoir, porosity, oil saturation, clay interlayers, carbonate-anhydrite inclusions
Authors: A.V. Akin’shin, V.A. Efimov, E.A. Rakitin (Tyumen Branch of SurgutNIPIneft, RF, Tyumen)

In determining the parameters of heterogeneous core rock, homogeneous samples are usually studied, which makes it impossible to establish reliable relationships of the ‘core – log’ type. The use of parameters of homogeneous samples in the search for dependencies leads to overestimation of the reservoir capacity and to a decrease (in reservoirs with a thin interbedding of sandstones and clays) or to an overestimation (in reservoirs with focal carbonate-anhydrite inclusions) of the oil and gas saturation coefficient. The authors proposed a method for accounting for two-component (sandy-argillaceous reservoir contains puffs, inclusions and lenses of clayey material) and a three-component (the reservoir contains impermeable carbonate-anhydrite inclusions along with thin-layered clay interlayers and inclusions) texture heterogeneity in determining the parameters of terrigenous reservoirs according to the data of standard complex of well logging. The work is based on the results of special computer processing of photographs of a full-length core, routine studies of filtration-capacitive properties and results of geophysical studies of wells. Accumulations are provided for calculating the volume content of the texture components of the reservoir in accordance with the complex of geophysical methods. The convergence between the calculated volume contents of textural components according to the geophysical methods and the cores determined from the photographs is 0.15. The change in the oil-gas-saturation coefficient of the reservoir layer is shown depending on the content of clay (two-component textured heterogeneity) and clay and carbonate-anhydrite inclusions (three-component textured heterogeneity). In reservoir with a three-component textured heterogeneity, the effect of impermeable interlayers and inclusions is differently directed. With increasing content in the layer of the reservoir of clay interlayers, the oil-gas-saturation of the sandy interlayer increases, while with an increase in the share of focal carbonate-anhydrite inclusions, it decreases. The proposed method for taking into account the texture inhomogeneity of terrigenous reservoirs excludes systematic errors in determining the counting parameters of the reservoirs according to the complex of well logging.

References

1. Efimov V.A., Akmanaev A.R., Akin'shin A.V., Determining the proportion of clay layers from core photographs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 10, pp. 88–90.

2. Akin'shin A.V., A method for determining the area of texture components on photos of core samples of textural inhomogeneous rocks (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2016, no. 1, pp. 28–31.

3. Astashkin D.A., Razrabotka petrofizicheskoy modeli neodnorodnykh peschano-alevritovykh porod-kollektorov s tsel’yu povysheniya dostovernosti kolichestvennoy interpretatsii dannykh GIS (na primere nekotorykh mestorozhdeniy Zapadnoy i Vostochnoy Sibiri) (Development of petrophysical model of inhomogeneous sand-silt reservoir rocks in order to increase the reliability of the quantitative interpretation of log data (for example, Western and Eastern Siberia oil fields)): thesis of candidate of geological and mineralogical science, Moscow, 2005.

4. Lopatin A.Yu., Medvedev A.L., Masalkin Yu.V., Valensia R., Log interpretation methodology in polygenetic deposits of the Vikulovskaya suite at the Kamennoye field (thin-layer storm deposits and incised valley fill complex)  (In Russ.), SPE 115490, 2008.

5. Akin'shin A.V., Efimov V.A., Development of algorithms of logging data interpretation for volumetric parameters accuracy enhancement (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 11, pp. 87–89.

In determining the parameters of heterogeneous core rock, homogeneous samples are usually studied, which makes it impossible to establish reliable relationships of the ‘core – log’ type. The use of parameters of homogeneous samples in the search for dependencies leads to overestimation of the reservoir capacity and to a decrease (in reservoirs with a thin interbedding of sandstones and clays) or to an overestimation (in reservoirs with focal carbonate-anhydrite inclusions) of the oil and gas saturation coefficient. The authors proposed a method for accounting for two-component (sandy-argillaceous reservoir contains puffs, inclusions and lenses of clayey material) and a three-component (the reservoir contains impermeable carbonate-anhydrite inclusions along with thin-layered clay interlayers and inclusions) texture heterogeneity in determining the parameters of terrigenous reservoirs according to the data of standard complex of well logging. The work is based on the results of special computer processing of photographs of a full-length core, routine studies of filtration-capacitive properties and results of geophysical studies of wells. Accumulations are provided for calculating the volume content of the texture components of the reservoir in accordance with the complex of geophysical methods. The convergence between the calculated volume contents of textural components according to the geophysical methods and the cores determined from the photographs is 0.15. The change in the oil-gas-saturation coefficient of the reservoir layer is shown depending on the content of clay (two-component textured heterogeneity) and clay and carbonate-anhydrite inclusions (three-component textured heterogeneity). In reservoir with a three-component textured heterogeneity, the effect of impermeable interlayers and inclusions is differently directed. With increasing content in the layer of the reservoir of clay interlayers, the oil-gas-saturation of the sandy interlayer increases, while with an increase in the share of focal carbonate-anhydrite inclusions, it decreases. The proposed method for taking into account the texture inhomogeneity of terrigenous reservoirs excludes systematic errors in determining the counting parameters of the reservoirs according to the complex of well logging.

References

1. Efimov V.A., Akmanaev A.R., Akin'shin A.V., Determining the proportion of clay layers from core photographs (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 10, pp. 88–90.

2. Akin'shin A.V., A method for determining the area of texture components on photos of core samples of textural inhomogeneous rocks (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2016, no. 1, pp. 28–31.

3. Astashkin D.A., Razrabotka petrofizicheskoy modeli neodnorodnykh peschano-alevritovykh porod-kollektorov s tsel’yu povysheniya dostovernosti kolichestvennoy interpretatsii dannykh GIS (na primere nekotorykh mestorozhdeniy Zapadnoy i Vostochnoy Sibiri) (Development of petrophysical model of inhomogeneous sand-silt reservoir rocks in order to increase the reliability of the quantitative interpretation of log data (for example, Western and Eastern Siberia oil fields)): thesis of candidate of geological and mineralogical science, Moscow, 2005.

4. Lopatin A.Yu., Medvedev A.L., Masalkin Yu.V., Valensia R., Log interpretation methodology in polygenetic deposits of the Vikulovskaya suite at the Kamennoye field (thin-layer storm deposits and incised valley fill complex)  (In Russ.), SPE 115490, 2008.

5. Akin'shin A.V., Efimov V.A., Development of algorithms of logging data interpretation for volumetric parameters accuracy enhancement (In Russ.), Neftyanoe khozyaystvo = Oil Industry, 2013, no. 11, pp. 87–89.



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