A three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method and device

Abstract

The present invention relates to a three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method. This method primarily addresses the problem that existing technologies are unable to accurately calculate the saturation of low-resistance shale reservoirs through electrical logging. The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method includes: establishing a shale rock equivalent physical volume model based on logging data; establishing a shale formation resistivity anisotropy model based on the shale rock equivalent physical volume model; and establishing an electrical oil saturation calculation model based on the shale formation oil-bearing resistivity anisotropy model. The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method improves the accuracy of shale reservoir logging saturation calculations and can achieve accurate oil-bearing evaluation of shale oil reservoirs.

Description

Technical field:

[0001] The present invention relates to the technical field of well logging evaluation of complex reservoir fluid properties in petroleum exploration, and in particular to a method and device for quantitatively calculating saturation of a three-dimensional inductive anisotropic shale reservoir. Background technology:

[0002] Mudstone formations are effective source rocks. Organic-rich mudstone, shale, or thinly interbedded oil-bearing siltstone and marl reservoirs are typical self-generating and self-storing reservoirs. Well logging evaluation techniques for shale reservoirs are primarily based on sandstone or limestone, and no evaluation method based on shale saturation interpretation has been developed. Currently, shale in China is primarily mudstone, with a mud content exceeding 85% and a diverse mineral composition, primarily clay and quartz, with clay content of 40% and quartz content of 37%. Thin interbeds are difficult to identify due to the limited resolution of logging instruments, posing new challenges to well logging lithologic interpretation and evaluation. When the lithology and fluid properties of a shale reservoir simultaneously influence the electrical properties of the reservoir, the measured absolute resistivity value cannot accurately reflect the reservoir properties. Using shale evaluation methods primarily based on sandstone or limestone to calculate the formation's oil and gas saturation can lead to miscalculations and underestimate oil and gas reserves. Existing electrical logging technology has no applicable saturation model for low-resistance shale reservoirs, and electrical logging cannot characterize the saturation of shale reservoirs. The non-electrical TOC and S1 saturation calculation results for Gulong shale oil (when oil and gas coexist) are too low. The measurement accuracy of TOC and S1 (measuring liquid hydrocarbons) is greatly affected by the diffusion speed of oil and gas and the measurement time, and TOC and S1 cannot accurately characterize the gas content. Summary of the invention:

[0003] The present invention aims to overcome the prior art's inability to accurately calculate saturation in low-resistance shale reservoirs using electrical logging. It instead provides a three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method. This three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method improves the accuracy of shale reservoir saturation calculations using well logging, enabling accurate evaluation of shale oil reservoir oil content. The present invention also provides a three-dimensional induction anisotropic shale reservoir saturation quantitative calculation device.

[0004] To achieve the above objectives, the present invention provides a first aspect of a method for quantitatively calculating saturation of a three-dimensional inductive anisotropic shale reservoir, the method comprising:

[0005] Based on well logging data, an equivalent physical volume model of shale rock is established;

[0006] Based on the equivalent physical volume model of shale rock, an anisotropy model of shale formation resistivity is established;

[0007] Based on the resistivity anisotropy model of oil-bearing properties in shale formations, an electrical oil saturation calculation model was established.

[0008] Furthermore, the method for establishing the equivalent physical volume model of shale rock includes:

[0009] In shale reservoirs, the rock volume is composed of sandstone volume, mudstone volume, calcareous volume, and pore volume;

[0010] The volume percentage of sandstone, calcareous rock and mudstone is calculated using the formation element logging data processing module; the total porosity of the rock is calculated using the nuclear magnetic data processing module. Effective porosity φ e Two pore volume parameters;

[0011] According to the obtained volume proportion of sandstone, calcareous and mudstone and the total porosity of rock Establish an equivalent physical volume model of shale rock.

[0012] Furthermore, a method for establishing an anisotropic resistivity model of oil-bearing shale formation includes:

[0013] In shale reservoirs, resistivity anisotropy is composed of lithologic anisotropy and fluid anisotropy. The resistivity anisotropy is obtained by the square root of the ratio of the vertical resistivity measured perpendicular to the rock formation to the horizontal resistivity measured parallel to the formation.

[0014] The resistivity anisotropy of different lithologies is obtained by using the rock resistivity anisotropy physical experiment; the volume fraction of sandstone, calcareous rock, and mudstone is calculated using the formation element logging data processing module;

[0015] resistivity anisotropy measured by 3D induction imaging logging;

[0016] The resistivity anisotropy measured by 3D induction imaging logging was corrected to eliminate the influence of lithologic anisotropy and obtain the resistivity anisotropy value of the oil content of the shale formation.

[0017] Furthermore, the method for determining the electrical oil saturation calculation model includes:

[0018] The shale oil saturation model is determined by using the relationship between the shale oil saturation and the oil resistivity anisotropy value of the shale formation analyzed by the core laboratory;

[0019] The established shale oil saturation model is used to calculate the saturation under reservoir conditions and generate the shale saturation corresponding to different logging depths.

[0020] Furthermore, the equivalent physical volume model of shale rock is:

[0021]

[0022] Anisotropic resistivity model of oil content in shale formations:

[0023] λ oil =λ L -(λ sand V sand +λ shale V shale +λ calc V calc ) (2)

[0024] Shale oil saturation model:

[0025]

[0026] Where: V sand is the volume ratio of sandstone; V shale is the volume ratio of mudstone; V calc is the volume fraction of fluid in rock; is the total porosity of the rock, in decimal units; λ sand is the resistivity anisotropy of sandstone; shale is the resistivity anisotropy of shale; calc is the anisotropy of calcium resistivity; λ L Resistivity anisotropy obtained from 3D induction logging; λ oil is the resistivity anisotropy value of the oil-bearing shale formation; Δλ is the three-dimensional induction resistivity change per unit pore volume; S o is the oil and gas saturation, in decimal units; φ e is the effective porosity, in decimals; k is the scale conversion coefficient, in decimals; n is the exponential coefficient, in decimals.

[0027] Furthermore, the logging data includes electrical parameters, lithologic mineral component parameters, and rock porosity parameters; the electrical parameters are vertical resistivity and horizontal resistivity; the lithologic mineral parameters are mineral components and mineral content; the mineral components include sandstone, mudstone, and calcareous; the mineral content includes sandstone volume, mudstone volume, and calcareous volume; the rock porosity parameters are total rock porosity and effective porosity; the total rock porosity includes matrix pores and secondary pores.

[0028] In order to achieve the above object, the present invention provides, in another aspect, a device for quantitatively calculating saturation of a three-dimensional inductive anisotropic shale reservoir, the device comprising:

[0029] Characterization module: Sandstone volume fraction, mudstone volume fraction and calcareous layer volume fraction (V sand , V shale , Vcalc ), which is used to characterize the volume proportion of sandstone, mudstone and calcareous layer in the equivalent physical volume model of shale rock (V sand , V shale , V calc ); Total rock porosity of shale reservoir determined based on nuclear magnetic resonance logging data Effective porosity φ e , used to characterize the rock porosity and total rock porosity in the equivalent physical volume model of shale rock Effective porosity φ e ; Use the horizontal resistivity and vertical resistivity curves measured by 3D induction imaging logging to characterize the resistivity anisotropy value λ of the shale reservoir L ;

[0030] Calibration module: Select typical rock samples of the target layer and determine the resistivity anisotropy values ​​(λ) of sandstone, calcareous and mudstone through three-dimensional resistivity anisotropy test calibration. sand ,λ shale ,λ calc ), and the k and n values ​​were determined by calibrating the relationship between the oil content of shale oil and the resistivity anisotropy value of the oil content of shale formations through core experiment analysis;

[0031] Calculation module: Calculate the resistivity anisotropy value λ of the oil-bearing resistivity of the shale formation based on the resistivity anisotropy values ​​of sandstone, calcareous rock and mudstone generated by the calibration module oil The k and n values ​​determined by the calibration module are substituted into the following saturation calculation formula to calculate the oil saturation of the shale reservoir.

[0032] Compared with the above background technology, the present invention has the following beneficial effects:

[0033] The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method of the present invention establishes an equivalent rock physics model of shale resistivity anisotropy and a shale oil saturation calculation model. Based on core analysis experiments, it eliminates the influence of lithologic anisotropy and determines relevant parameters of the calculation model, thereby accurately determining the oil saturation of the shale reservoir. The saturation quantitative calculation method characterized by the present invention solves the problem that the existing technology cannot accurately calculate the saturation of low-resistance shale reservoirs through electrical logging. It improves the accuracy of shale reservoir logging saturation calculations and can accurately evaluate the oil content of shale oil reservoirs. Field applications have demonstrated that the model is stable, reliable, and highly applicable, and can quickly and accurately calculate the oil saturation of shale reservoirs. Description of the drawings:

[0034] Attachment Figure 1 A flow chart of a method for quantitatively calculating shale reservoir saturation provided by an embodiment of the present invention;

[0035] Attachment Figure 2 This is a diagram of the shale reservoir interpretation model obtained by laboratory shale oil content analysis in the present invention;

[0036] Attachment Figure 3 This is a diagram showing the interpretation results of actual logging data obtained using a three-dimensional induction logging tool provided in an embodiment of the present invention. Specific implementation method:

[0037] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0038] Figure 1 FIG. 1 shows a shale reservoir interpretation model diagram obtained by laboratory shale oil content analysis according to an embodiment of the present invention; FIG. Figure 1 As shown in FIG, the process of the calculation method mainly consists of four links, including the following steps: inputting the original logging data to establish an equivalent physical volume model S101, preprocessing the logging data to eliminate the anisotropy of lithologic resistivity S202, characterizing the shale reservoir saturation model S302, and calculating the saturation of the sandstone and mudstone formations S302.

[0039] Figure 2 This diagram shows a shale reservoir interpretation model derived from laboratory analysis of shale oil content. Laboratory analysis of 940 cores from four wells revealed the relationship between shale oil content and resistivity anisotropy within the shale formation. This established a shale oil saturation model, which was then used to calculate saturation under these reservoir conditions. The ordinate represents the one-dimensional nuclear magnetic resonance saturation from field core analysis using sealed coring, while the abscissa represents the change in resistivity anisotropy per unit effective pore volume within the oil-bearing shale.

[0040] According to a first aspect of an embodiment of the present invention, a method for quantitatively calculating saturation of a three-dimensional inductive anisotropic shale reservoir is provided, the method comprising:

[0041] 1. Establish an equivalent physical volume model of shale rock; the method includes:

[0042] 1) In shale reservoirs, the rock volume is composed of sandstone volume, mudstone volume, calcareous volume, and the volume occupied by pores;

[0043] 2) Use the formation element logging data processing module to calculate the volume percentage of sandstone, calcareous rock, and mudstone; use the nuclear magnetic data processing module to calculate the total porosity of the rock Effective pore volume φ e

[0044] 3) According to the obtained volume proportion of sandstone, calcareous and mudstone and the total porosity of rock Establish an equivalent physical volume model of shale rock. The equivalent physical volume model of shale rock is as shown in Formula 1:

[0045]

[0046] Where: V sand is the volume ratio of sandstone; V shale is the volume ratio of mudstone; V calc is the volume fraction of fluid in rock; is the rock porosity, in decimal units;

[0047] 2. Based on the equivalent physical volume model of shale rock, establish an anisotropic resistivity model of oil content in shale formations; the method includes:

[0048] 1) In shale reservoirs, resistivity anisotropy is composed of lithologic anisotropy and fluid anisotropy. The resistivity anisotropy is obtained by the square root of the ratio of the vertical resistivity measured perpendicular to the rock formation to the horizontal resistivity measured parallel to the formation.

[0049] 2) The resistivity anisotropy of different lithologies is obtained using the rock resistivity anisotropy physical experiment; the volume fraction of sandstone, calcareous rock, and mudstone is calculated using the formation element logging data processing module;

[0050] 3) Resistivity anisotropy measured by 3D induction imaging logging;

[0051] 4) The resistivity anisotropy measured by 3D induction imaging logging is corrected to eliminate the influence of lithologic anisotropy and obtain the resistivity anisotropy value of the oil content of the shale formation.

[0052] The resistivity anisotropy model of oil content in shale formations is as follows:

[0053] λ oil =λ L -(λ sand V sand +λ shale V shale +λ calc V calc ) (2)

[0054] Where: sand is the resistivity anisotropy of sandstone; shale is the resistivity anisotropy of shale; calc is the anisotropy of calcium resistivity; λ L Resistivity anisotropy obtained from 3D induction logging; λ oil is the resistivity anisotropy value of the oil-bearing shale formation;

[0055] 3. Based on the anisotropic resistivity model of oil-bearing properties in shale formations, an electrical oil saturation calculation model is established; the method includes:

[0056] 1) The relationship between the oil saturation of shale and the oil resistivity anisotropy value of shale formations analyzed by core laboratory (see Figure 2 ), determine the shale oil saturation model;

[0057] 2) The established saturation model is used to calculate the saturation under reservoir conditions and generate the shale saturation corresponding to different logging depths.

[0058] The electrical oil saturation calculation model is as shown in the following formula 3:

[0059]

[0060] Where Δλ is the change in three-dimensional induced resistivity per unit pore volume, S o is the oil and gas saturation, in decimal units; φ e is the effective porosity, in decimals; k is the scale conversion coefficient, in decimals; n is the exponential coefficient, in decimals.

[0061] The parameters in the three models are determined as follows:

[0062] ①V sand , V shale , V calc The volume proportions of sandstone, mudstone and calcareous interlayers can be calculated through the formation element logging data processing module;

[0063] ②λ sand ,λ shale ,λ calc It can be obtained through physical experimental testing of rock resistivity anisotropy;

[0064] ③λ L It can be obtained from the Rh horizontal and Rv vertical curves measured by three-dimensional induction imaging logging data; the resistivity anisotropy refers to the square root of the ratio of the resistivity measured perpendicular to the formation and the resistivity measured parallel to the formation.

[0065] ④The k value is obtained through statistical analysis of oil content experimental data of multiple samples;

[0066] ⑤φ e It can be calculated using the nuclear magnetic data processing module;

[0067] ⑥The n value is obtained through statistical analysis of oil content experimental data of multiple samples;

[0068] Verification of electrical oil saturation calculation model:

[0069] like Figure 3As shown, the verification was carried out based on a key well, Guye 2HC, in the Gulong shale oil block of Daqing Oilfield.

[0070] By analyzing the core data of three wells in the Guye 1 well area of ​​the Gulong mud shale in Daqing, we obtained k = 20.574, n = -0.635. Taking k = 20.574, n = -0.635, the oil saturation of the Daqing mud shale is calculated using the following formula:

[0071]

[0072] According to another aspect of an embodiment of the present invention, a device for quantitatively calculating saturation of a three-dimensional inductive anisotropic shale reservoir is provided, the device comprising:

[0073] Characterization module: Use lithologic scanning logging data to determine the volume fraction of sandstone, mudstone and calcareous layer (V sand , V shale , V calc ), which is used to characterize the volume proportion of sandstone, mudstone and calcareous layer in the equivalent physical volume model of shale rock (V sand , V shale , V calc ) ; Determine the rock porosity of shale reservoirs using nuclear magnetic resonance logging data Effective porosity φ e , used to characterize the rock porosity in the equivalent physical volume model of shale rock, Effective porosity φ e ; Use the horizontal resistivity and vertical resistivity curves measured by 3D induction imaging logging to characterize the resistivity anisotropy value λ of shale reservoir L ;

[0074] Calibration module: Select typical rock samples of the target layer and determine the resistivity anisotropy values ​​(λ) of sandstone, calcareous and mudstone through three-dimensional resistivity anisotropy test. sand ,λ shale ,λ calc ), and the values ​​of k and n are determined by analyzing the relationship between the oil content of shale oil and the resistivity anisotropy value of the oil content of shale formations through core experiments;

[0075] Calculation module: Calculate the resistivity anisotropy value λ of the oil-bearing resistivity of the shale formation based on the resistivity anisotropy values ​​of sandstone, calcareous rock and mudstone generated by the calibration module oil The k and n values ​​determined by the calibration module are substituted into the following saturation calculation formula to calculate the oil saturation of the shale reservoir.

[0076] To further clarify the objectives, technical solutions, and advantages of the present invention, a method and apparatus for quantitatively calculating saturation in shale reservoirs using three-dimensional sensing anisotropy is proposed for the Gulong shale oil block in the Daqing Oilfield. The detailed description of this method below includes detailed descriptions of certain specific steps. However, any portions not fully described will be readily understood by those skilled in the art.

[0077] Example 1

[0078] Figure 3 The present invention provides a three-dimensional induction logging instrument measured data processing result. First, the formation element logging data processing module is used to process the formation element logging data of the Guye 2HC well to obtain the volume percentage of sandstone, calcareous rock, and mudstone, that is, V sand , V shale , V calc The total porosity of the rock was obtained by processing the nuclear magnetic logging data of Guye 2HC well using the nuclear magnetic data processing module. Effective pore volume φ e , the resistivity anisotropy λ measured by 3D induction imaging logging in Guye 2HC well L , we can get λ by calculating oil , using the established three-dimensional induction anisotropic shale reservoir saturation model The oil saturation of the shale reservoir in the Guye 2HC well was generated. In the comprehensive interpretation comparison chart for the Guye 2HC well, the first track is the geological stratification track, with the target layer being the Qing 2 Member. The second track is the lithologic curve track, with the GR curve exhibiting a micro-dentate distribution, a typical curve characteristic of shale. The third track is the depth track, with the well section selected between 2200 and 2320 m. Tracks 4 and 5 are core retrieval profile tracks. Track 6 is the lateral logging track, with deep and shallow laterals essentially overlapping in the less permeable shale reservoir section. Track 7 shows the horizontal and vertical resistivity obtained from 3D induction logging. The yellow fill indicates the difference between horizontal and vertical resistivity, indicating that resistivity in different directions in the reservoir clearly reflects fluid properties. Resistivity differences in single fluids are small, while those in mixed fluids are large. The Qing 2 Member exhibits significant anisotropy overall. The eighth channel is a reservoir evaluation channel. Both the total porosity and effective porosity derived from NMR data indicate that the shale reservoir has poor physical properties, with an average total porosity between 10% and 12%. Lithologic scanning logging reveals that the Qing-2 reservoir is composed of sand, calcareous rock, and a significant amount of mud. The ninth channel is an oil content evaluation channel. The first two channels compare resistivity anisotropy with S1 content and total hydrocarbon content. Resistivity anisotropy and S1 content show good correlation in all other reservoir sections, with some discrepancies observed in reservoir layer 90. Comparison with total hydrocarbon content shows a high degree of agreement across the entire reservoir section, with relatively consistent results and a reasonable degree of correlation. The third channel compares oil saturation derived from NMR data with oil saturation calculated using 3D induction. The two results also show a reasonable correlation, confirming the accuracy of the oil saturation calculated using this method. Using the established saturation model for this reservoir, water saturation for the shale reservoir corresponding to different logging depths was generated.

Claims

1. A three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method, characterized by: include: Based on well logging data, an equivalent physical volume model of shale rock is established; Based on the equivalent physical volume model of shale rock, an anisotropy model of shale formation resistivity is established; Based on the anisotropic resistivity model of oil-bearing properties in shale formations, an electrical oil saturation calculation model was established. The equivalent physical volume model of shale rock is: Anisotropic resistivity model of oil content in shale formations: l oil =λ L -(l sand V sand +λ shale V shale +λ calc V calc ) (2) Shale oil saturation model: Where: V sand is the volume ratio of sandstone; V shale is the volume ratio of mudstone; V calc is the volume fraction of fluid in rock; is the total porosity of the rock, in decimal units; λ sand is the resistivity anisotropy of sandstone; shale is the resistivity anisotropy of shale; calc is the anisotropy of calcium resistivity; λ L is the resistivity anisotropy value of shale reservoir; oil is the resistivity anisotropy value of the oil-bearing shale formation; S o is the oil and gas saturation, in decimal units; φ e is the effective porosity, in decimals; k is the scale conversion coefficient, in decimals; n is the exponential coefficient, in decimals; λ sand ,λ shale ,λ calc Through the physical experiment test of rock resistivity anisotropy, it is obtained that: typical rock samples of the target layer are selected, and the resistivity anisotropy values ​​of sandstone, calcareous and mudstone are determined through the three-dimensional resistivity anisotropy experimental test calibration.

2. The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method according to claim 1 is characterized by: The method for establishing the equivalent physical volume model of shale rock includes: In shale reservoirs, the rock volume is composed of sandstone volume, mudstone volume, calcareous volume and pore volume. The volume percentage of sandstone, calcareous volume and mudstone volume is calculated using the formation element logging data processing module. The total porosity of the rock is calculated using the nuclear magnetic data processing module. Effective porosity φ e Two pore volume parameters; based on the obtained sandstone, calcareous, mudstone volume fraction and total rock porosity Establish an equivalent physical volume model of shale rock.

3. The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method according to claim 1 is characterized by: The method for establishing an anisotropic resistivity model of oil-bearing properties in shale formations includes: In shale reservoirs, resistivity anisotropy is composed of lithologic anisotropy and fluid anisotropy. The resistivity anisotropy is obtained by the square root of the ratio of the vertical resistivity measured perpendicular to the rock formation to the horizontal resistivity measured parallel to the formation. The resistivity anisotropy of different lithologies is obtained by using the rock resistivity anisotropy physical experiment; the volume percentage of sandstone, calcareous rock, and mudstone is calculated using the formation element logging data processing module; resistivity anisotropy measured by 3D induction imaging logging; The resistivity anisotropy measured by 3D induction imaging logging was corrected to eliminate the influence of lithologic anisotropy and obtain the resistivity anisotropy value of the oil content of the shale formation.

4. The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method according to claim 1 is characterized by: The method for determining the electrical oil saturation calculation model includes: The shale oil saturation model is determined by using the relationship between the shale oil saturation and the oil resistivity anisotropy value of the shale formation analyzed by the core laboratory; The established shale oil saturation model is used to calculate the saturation under reservoir conditions and generate the shale saturation corresponding to different logging depths.

5. The three-dimensional induction anisotropic shale reservoir saturation quantitative calculation method according to claim 1 is characterized by: The logging data includes electrical parameters, lithologic mineral component parameters, and rock porosity parameters; the electrical parameters are vertical resistivity and horizontal resistivity; the lithologic mineral parameters are mineral components and mineral content; the mineral components include sandstone, mudstone, and calcareous; the mineral content includes sandstone volume, mudstone volume, and calcareous volume; the rock porosity parameters are total rock porosity and effective porosity; the total rock porosity includes matrix pores and secondary pores.

6. A three-dimensional induction anisotropic shale reservoir saturation quantitative calculation device, characterized in that: The device includes: Characterization module: The sandstone volume fraction, mudstone volume fraction and calcareous layer volume fraction determined based on lithologic scanning logging data are used to characterize the sandstone volume fraction, mudstone volume fraction and calcareous layer volume fraction in the equivalent physical volume model of shale rock; the total rock porosity of shale reservoir determined based on nuclear magnetic resonance logging data Effective porosity φ e , used to characterize the rock porosity and total rock porosity in the equivalent physical volume model of shale rock Effective porosity φ e ; Use the horizontal resistivity and vertical resistivity curves measured by 3D induction imaging logging to characterize the resistivity anisotropy value λ of the shale reservoir L ; Calibration module: Select typical rock samples of the target layer and calibrate the resistivity anisotropy values ​​of sandstone, calcareous rock, and mudstone through three-dimensional resistivity anisotropy test. Analyze the relationship between the oil content of shale oil and the resistivity anisotropy value of the shale formation through core experiment to determine the k and n values. The k and n values ​​are determined according to the shale oil saturation model: Calculation module: Calculate the resistivity anisotropy value λ of the oil-bearing resistivity of the shale formation based on the resistivity anisotropy values ​​of sandstone, calcareous rock and mudstone generated by the calibration module oil , and substitute the k and n values ​​determined by the calibration module into the following saturation calculation formula to calculate the oil saturation of the shale reservoir; The method for obtaining the oil-bearing resistivity anisotropy value λ of the shale formation oil The specific model is: l oil =λ L -(l sand V sand +λ shale V shale +λ calc V calc ) (2) The shale oil saturation model is:

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