Permeability-porosity relation and preferential flow in heterogeneous vuggy carbonates

Hikaru Kusanagi; Noriaki Watanabe; Takashi Shimazu; Masahiko Yagi

Permeability-porosity relation and preferential flow in heterogeneous vuggy carbonates

Hikaru Kusanagi, Noriaki Watanabe, Takashi Shimazu, Masahiko Yagi

ENV - Environmental Studies for Advanced Society

Research output: Contribution to conference › Paper › peer-review

1 Citation (Scopus)

Abstract

The present study investigates fluid flows and permeabilities through vuggy carbonates via a single-phase fluid-flow experiment and a numerical model simulation using X-ray CT. 3D imaging of flow paths in vuggy carbonate samples reveals that fluid flows through vuggy carbonates are generally characterized by the formation of preferential flow paths due to heterogeneous porosity distributions within the rocks. Only a part of pores (typically <50% of the total pore volume) effectively contributes to the flow, while the other pores contain stagnant fluids. Histograms of local porosity for all samples are characterized by lognormal distributions with different geometric mean, mφ (fraction), and standard deviation, σφ, values, depending on the heterogeneities of the rocks. Percentage of the pore volume that effectively contributes to the flow over the total pore volume, VF, which results from the formation of preferential flow paths, linearly decreases with increasing the geometric standard deviation, i.e. intensity of formation of vug pores or spatial correlation of pores: VF = -155σφ + 255. Global permeabilities of the samples are not related to their He porosities, unlike those of non-vuggy carbonates, because of the fact that a part of pores contributes to the flows. In case of vuggy carbonates, the global permeability, K (m²), is a function of both the geometric mean and standard deviation values, where the larger geometric mean and standard deviation values are, the higher the global permeability is. A new permeability-porosity relation of vuggy carbonates, in addition to the existing class I-III relations of non-vuggy carbonates, namely class IV (four) relation is found to be described as K = 4.573×10^-10 ΦIV7.77, where ΦIV = mφ × σφ2 is a modified fractional porosity for vuggy carbonates having Interparticle and Vug (IV) porosities. This equation implies that the global permeability is higher for vuggy carbonates having more spatially correlated (σφ ) larger pores (mφ × σφ).

Original language	English
Publication status	Published - 2015 Jan 1
Event	21st Formation Evaluation Symposium of Japan 2015 - Chiba, Japan Duration: 2015 Oct 13 → 2015 Oct 14

Other

Other	21st Formation Evaluation Symposium of Japan 2015
Country	Japan
City	Chiba
Period	15/10/13 → 15/10/14

ASJC Scopus subject areas

Energy Engineering and Power Technology
Economic Geology
Geochemistry and Petrology
Geotechnical Engineering and Engineering Geology
Geology

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title = "Permeability-porosity relation and preferential flow in heterogeneous vuggy carbonates",

abstract = "The present study investigates fluid flows and permeabilities through vuggy carbonates via a single-phase fluid-flow experiment and a numerical model simulation using X-ray CT. 3D imaging of flow paths in vuggy carbonate samples reveals that fluid flows through vuggy carbonates are generally characterized by the formation of preferential flow paths due to heterogeneous porosity distributions within the rocks. Only a part of pores (typically <50% of the total pore volume) effectively contributes to the flow, while the other pores contain stagnant fluids. Histograms of local porosity for all samples are characterized by lognormal distributions with different geometric mean, mφ (fraction), and standard deviation, σφ, values, depending on the heterogeneities of the rocks. Percentage of the pore volume that effectively contributes to the flow over the total pore volume, VF, which results from the formation of preferential flow paths, linearly decreases with increasing the geometric standard deviation, i.e. intensity of formation of vug pores or spatial correlation of pores: VF = -155σφ + 255. Global permeabilities of the samples are not related to their He porosities, unlike those of non-vuggy carbonates, because of the fact that a part of pores contributes to the flows. In case of vuggy carbonates, the global permeability, K (m2), is a function of both the geometric mean and standard deviation values, where the larger geometric mean and standard deviation values are, the higher the global permeability is. A new permeability-porosity relation of vuggy carbonates, in addition to the existing class I-III relations of non-vuggy carbonates, namely class IV (four) relation is found to be described as K = 4.573×10-10 ΦIV7.77, where ΦIV = mφ × σφ2 is a modified fractional porosity for vuggy carbonates having Interparticle and Vug (IV) porosities. This equation implies that the global permeability is higher for vuggy carbonates having more spatially correlated (σφ ) larger pores (mφ × σφ).",

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AU - Kusanagi, Hikaru

AU - Watanabe, Noriaki

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N2 - The present study investigates fluid flows and permeabilities through vuggy carbonates via a single-phase fluid-flow experiment and a numerical model simulation using X-ray CT. 3D imaging of flow paths in vuggy carbonate samples reveals that fluid flows through vuggy carbonates are generally characterized by the formation of preferential flow paths due to heterogeneous porosity distributions within the rocks. Only a part of pores (typically <50% of the total pore volume) effectively contributes to the flow, while the other pores contain stagnant fluids. Histograms of local porosity for all samples are characterized by lognormal distributions with different geometric mean, mφ (fraction), and standard deviation, σφ, values, depending on the heterogeneities of the rocks. Percentage of the pore volume that effectively contributes to the flow over the total pore volume, VF, which results from the formation of preferential flow paths, linearly decreases with increasing the geometric standard deviation, i.e. intensity of formation of vug pores or spatial correlation of pores: VF = -155σφ + 255. Global permeabilities of the samples are not related to their He porosities, unlike those of non-vuggy carbonates, because of the fact that a part of pores contributes to the flows. In case of vuggy carbonates, the global permeability, K (m2), is a function of both the geometric mean and standard deviation values, where the larger geometric mean and standard deviation values are, the higher the global permeability is. A new permeability-porosity relation of vuggy carbonates, in addition to the existing class I-III relations of non-vuggy carbonates, namely class IV (four) relation is found to be described as K = 4.573×10-10 ΦIV7.77, where ΦIV = mφ × σφ2 is a modified fractional porosity for vuggy carbonates having Interparticle and Vug (IV) porosities. This equation implies that the global permeability is higher for vuggy carbonates having more spatially correlated (σφ ) larger pores (mφ × σφ).

AB - The present study investigates fluid flows and permeabilities through vuggy carbonates via a single-phase fluid-flow experiment and a numerical model simulation using X-ray CT. 3D imaging of flow paths in vuggy carbonate samples reveals that fluid flows through vuggy carbonates are generally characterized by the formation of preferential flow paths due to heterogeneous porosity distributions within the rocks. Only a part of pores (typically <50% of the total pore volume) effectively contributes to the flow, while the other pores contain stagnant fluids. Histograms of local porosity for all samples are characterized by lognormal distributions with different geometric mean, mφ (fraction), and standard deviation, σφ, values, depending on the heterogeneities of the rocks. Percentage of the pore volume that effectively contributes to the flow over the total pore volume, VF, which results from the formation of preferential flow paths, linearly decreases with increasing the geometric standard deviation, i.e. intensity of formation of vug pores or spatial correlation of pores: VF = -155σφ + 255. Global permeabilities of the samples are not related to their He porosities, unlike those of non-vuggy carbonates, because of the fact that a part of pores contributes to the flows. In case of vuggy carbonates, the global permeability, K (m2), is a function of both the geometric mean and standard deviation values, where the larger geometric mean and standard deviation values are, the higher the global permeability is. A new permeability-porosity relation of vuggy carbonates, in addition to the existing class I-III relations of non-vuggy carbonates, namely class IV (four) relation is found to be described as K = 4.573×10-10 ΦIV7.77, where ΦIV = mφ × σφ2 is a modified fractional porosity for vuggy carbonates having Interparticle and Vug (IV) porosities. This equation implies that the global permeability is higher for vuggy carbonates having more spatially correlated (σφ ) larger pores (mφ × σφ).

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