# Shales Leaching Modelling for Prediction of Flowback Fluid Composition

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Shale Sample Acquisition

#### 2.2. Shale Sample Preparation

#### 2.3. Shale Samples Analysis

#### 2.4. Preparation of Model Fracturing Fluids

#### 2.5. Leaching Tests

^{2}) was above 0.85 were taken into consideration, the probability value for all describing variables was below 0.05 (variable values are not random), so the confidence level was always above 0.95 (note: R

^{2}coefficients are calculated for obtained model equations not for the residual analysis diagrams). In the next step only those equations for which all separate levels of confidence for every separate parameter were above 0.95 were considered. Then the model with the highest determination coefficient was chosen for further analysis. For chosen model the standard deviation was always the lowest taking into account considered models and its value justifies the correctness of application of R

^{2}as a crucial parameter to choose the most adequate model. The residual analysis showed a sufficient number of describing variables (small inclination angle to the abscissa) and there was no correlation between residuals and described variables (Pearson between −0.5 and 0.5). The Pearson coefficients were calculated for the correlation between elements concentrations in leachates and the residuals of the model. The residuals were calculated as the difference between laboratory and model data values. The model was selected basing on the comparison of the standard model error, the determination coefficient, the level of significance and the number of parameters relevant to the correct description of the model. Other parameters presented in the next section were calculated using statistical and mathematical methods implemented in RStudio software [43].

## 3. Results and Discussion

_{B}, c

_{Ba}, etc.) and variables. Residual analysis (difference between measured and calculated values) and maximum and minimum values calculated for the part of the model that can be influenced by controllable parameters of the fracturing fluid (c’

_{min}(60), c’

_{min}(80), c’

_{max}(60), c’

_{max}(80)) are presented in Table 5, Table 6, Table 7, Table 8, Table 9, Table 10, Table 11, Table 12 and Table 13. Composition of shales and temperature in the borehole are parameters of a particular well, therefore, we can change: IS, TOC and pH (by changing the fracturing fluid composition) so c’

_{B}, is a part of the whole c equation which can be manipulated and is used to calculate the possible range of changeability of the model by fracturing fluid parameter manipulations. The values of c’

_{min}and c’

_{max}were calculated for two extreme temperature values. It was calculated that the minimum and maximum values for all models are equal to 60 or 80 °C (minimum and maximum temperature). The differences between these values are presented in Table 14. These results indicate how much the concentration of the element in the flowback fluid can be reduced by proper control of the parameters of the fracturing fluid according to the developed models. Due to the statistical nature of the model, in some cases lowering the concentration could give a negative value. This should be taken into account when using and possibly implementing the model using a computer tool. Model fracturing fluids are characterized in Table 14.

## 4. Conclusions

^{2}as a crucial parameter to choose most adequate model. Residual analysis gives information that applied variables describes the model in the tested range well enough. Moreover, no correlation between residuals and measured values means that there are probably no methodological errors. Selected parameters of the model fracturing fluid and rock properties are sufficient to predict the composition of the flowback fluid in the laboratory system. In the next research other shale rock samples should be tested and data from analysis of flowback fluid for attempts to develop industrial version of the model need to be carried.

## Author Contributions

## Funding

## Conflicts of Interest

## Appendix A

No. Shale Sample | Mineral (%) | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

Quarz | Alb | Micr | Ort | Calc | Dol | Pir | Bar | Chl | Ill | Mon | Kao | Mus | Bio | Par | Gla | |

A1 | 15.89 | 2.93 | 1.58 | 1.10 | 9.38 | 2.56 | 6.70 | 2.43 | 4.75 | 1.10 | 0.00 | 9.38 | 38.29 | 0.36 | 2.56 | 0.98 |

A2 | 21.58 | 1.83 | 1.10 | 0.74 | 2.93 | 0.74 | 0.00 | 0.08 | 7.19 | 0.74 | 0.00 | 2.81 | 57.48 | 1.58 | 0.61 | 0.61 |

A3 | 12.74 | 2.07 | 2.68 | 0.61 | 28.67 | 8.53 | 0.00 | 0.12 | 3.77 | 0.48 | 10.73 | 5.85 | 18.64 | 2.93 | 1.83 | 0.36 |

A4 | 19.58 | 3.10 | 5.08 | 0.37 | 21.52 | 3.97 | 0.00 | 0.25 | 7.81 | 8.80 | 0.00 | 1.86 | 2.61 | 22.81 | 1.11 | 1.11 |

A5 | 23.73 | 0.98 | 0.86 | 0.37 | 22.81 | 4.80 | 0.00 | 0.12 | 9.34 | 2.83 | 0.12 | 11.55 | 19.17 | 0.62 | 0.86 | 1.85 |

A6 | 22.57 | 3.44 | 2.59 | 0.74 | 13.05 | 30.67 | 1.73 | 0.12 | 4.06 | 1.73 | 0.00 | 0.37 | 13.29 | 0.24 | 3.32 | 2.09 |

A7 | 13.60 | 2.70 | 3.19 | 0.12 | 12.86 | 33.97 | 0.12 | 0.12 | 5.03 | 3.19 | 0.24 | 0.36 | 17.27 | 4.53 | 0.50 | 2.20 |

A8 | 25.66 | 4.16 | 2.08 | 0.62 | 8.44 | 16.50 | 0.00 | 0.12 | 4.88 | 0.74 | 0.00 | 0.36 | 33.76 | 0.48 | 1.72 | 0.48 |

A9 | 34.97 | 6.67 | 3.52 | 1.00 | 9.17 | 11.19 | 0.76 | 0.12 | 5.04 | 2.13 | 0.00 | 2.13 | 5.53 | 3.77 | 1.51 | 12.47 |

A10 | 21.81 | 2.18 | 1.09 | 0.48 | 9.82 | 12.13 | 0.12 | 0.00 | 7.52 | 0.48 | 0.00 | 1.21 | 41.45 | 0.36 | 0.97 | 0.36 |

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**Table 1.**Comparison of concentrations of the most important components in fracturing fluid and flowback fluid from the Marcellus Shale [18].

Component | Fracturing Fluid | Flowback Fluid | ||
---|---|---|---|---|

Range of Concentrations (ppm) | Median Concentration (ppm) | Range of Concentrations (ppm) | Median Concentration (ppm) | |

Na^{+} | 25.70–6190 | 67.8 | 10700–65100 | 18000 |

Ca^{2+} | 6.70–2990 | 32.9 | 1440–23500 | 4950 |

Mg^{2+} | 1.20–235 | 6.7 | 135–1550 | 559 |

Fe^{2+} | 0.00–14.3 | 1.2 | 10.8–180 | 39 |

Ba^{2+} | 0.06–87.1 | 0.4 | 21.4–13900 | 686 |

Cl^{−} | 4.10–3000 | 42.3 | 26400–148000 | 41850 |

HCO_{3}^{−} | <1.00–188 | 49.9 | 29.8–162 | 74.4 |

NH_{4}^{+} | 0.58–441 | 5.9 | 15–242 | 82.4 |

No. | MFF | t (°C) | pH | IS (mol/L) | TOC (g/L) |
---|---|---|---|---|---|

X1 | X2 | X3 | X4 | ||

1 | P1 | 60 | 9 | 0.51 | 0.06 |

2 | P2 | 60 | 9 | 0.03 | 4.06 |

3 | P3 | 60 | 5 | 0.51 | 4.06 |

4 | P4 | 60 | 5 | 0.03 | 0.06 |

5 | P5 | 80 | 9 | 0.51 | 4060 |

6 | P6 | 80 | 9 | 0.03 | 0.06 |

7 | P7 | 80 | 5 | 0.51 | 0.06 |

8 | P8 | 80 | 5 | 0.03 | 4.06 |

9 | P9 | 80 | 7 | 0.51 | 4.06 |

10 | P10 | 60 | 7 | 0.03 | 0.06 |

11 | P11 | 80 | 9 | 0.51 | 2.06 |

12 | P12 | 60 | 5 | 0.03 | 2.06 |

13 | P13 | 70 | 7 | 0.27 | 2.06 |

14 | P13 | 70 | 7 | 0.27 | 2.06 |

15 | P13 | 70 | 7 | 0.27 | 2.06 |

No. of Sample | Element Concentration in the Shale Sample (CS) (ppm) | Aw (m^{2}/g) | TOC_{S} (%) | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|

B | Ba | Li | Mg | Mo | Rb | Si | Sr | Ca | |||

A1 | 4050 | 821 | 139 | 18240 | 10 | 3372 | 247285 | 401 | 116287 | 15.17 | 2.11 |

A2 | 3988 | 593 | 149 | 14820 | 95 | 3570 | 278445 | 175 | 35020 | 16.15 | 0.84 |

A3 | 3325 | 708 | 97 | 19570 | 82 | 2542 | 229900 | 605 | 179117 | 12.77 | 2.41 |

A4 | 3637 | 967 | 112 | 15960 | 9 | 3469 | 241965 | 179 | 131634 | 10.24 | 2.43 |

A5 | 3467 | 1208 | 110 | 17670 | 97 | 2578 | 262200 | 178 | 114948 | 10.67 | 2.72 |

A6 | 3694 | 774 | 115 | 23560 | 97 | 3369 | 262105 | 262 | 100013 | 14.05 | 1.40 |

A7 | 3361 | 1119 | 88 | 26695 | 82 | 3280 | 248045 | 212 | 123188 | 14.61 | 1.61 |

A8 | 3918 | 1455 | 122 | 20805 | 106 | 3068 | 273505 | 178 | 68804 | 9.72 | 4.40 |

A9 | 3425 | 1395 | 120 | 19665 | 100 | 2777 | 277400 | 154 | 58916 | 13.29 | 1.81 |

A10 | 3513 | 842 | 119 | 18335 | 105 | 3358 | 282150 | 140 | 59019 | 12.62 | 1.77 |

_{S}—Total organic carbon in shale sample, B, Ba, Li, etc.—symbols of the indicated elements, CS

_{X}—element X concentration in shale sample.

No. of Sample | Group of Minerals (%) | ||||
---|---|---|---|---|---|

G1 | G2 | G3 | G4 | G5 | |

A1 | 21.50 | 11.95 | 9.13 | 15.24 | 42.19 |

A2 | 25.25 | 3.66 | 0.08 | 10.74 | 60.28 |

A3 | 18.10 | 37.19 | 0.12 | 20.83 | 23.75 |

A4 | 28.14 | 25.49 | 0.25 | 18.47 | 27.64 |

A5 | 25.94 | 27.60 | 0.12 | 23.84 | 22.50 |

A6 | 29.33 | 43.72 | 1.85 | 6.16 | 18.94 |

A7 | 19.61 | 46.83 | 0.24 | 8.82 | 24.50 |

A8 | 32.52 | 24.94 | 0.12 | 5.98 | 36.44 |

A9 | 46.16 | 20.36 | 0.88 | 9.31 | 23.29 |

A10 | 25.56 | 21.96 | 0.12 | 9.22 | 43.15 |

B concentration in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{B} = −5155 + 35.6t − 549.7TOC − 74.7(TOC)^{2} − 341.7pH × IS + 25.5pH × TOC + 21.5t × IS + 9.3t × TOC − 211.6G1− 115.4G2 − 60.2G4 − 183.9G5 + 2.4CS_{B} − 81CS_{Mo} + 0.06CS_{Si} ± [286.4]c’ _{B} = −35.6t − 549.7TOC − 74.7 (TOC)^{2} − 341.7pH × IS + 25.5pH × TOC + 21.5t × IS + 9.3t × TOC | |||

R^{2} | 0.90 | Residual analysis | |

p | <0.000001 | ||

a | 0.0888 | ||

α = arctan (a) | 5.1° | ||

Pearson | 0.30 | ||

c_{min} (t = 60 °C) | 1238 ppb | ||

c_{max} (t = 60 °C) | 1967 ppb | ||

c_{min} (t = 80 °C) | 2181 ppb | ||

c_{max} (t = 80 °C) | 3159 ppb |

_{B}—concentration of boron in leachates; r

_{A}-residual in residual analysis; a—directional coefficient; arctan-arcus tangent which is equal to angle between regression line in residual analysis and 0x axis; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{B}, CS

_{Mo}, CS

_{Si-}B, Mo, Si concentrations in shale sample.

Ba concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Ba} = 1664 – 1792pH + 122pH^{2} + 43.8TOC^{2} + 157.7pH × IS − 3.14t × TOC − 48.73G2 − 118.41G3 − 271Aw − 0.44CS_{Ba}+ 34.44CS_{Li} + 0.276CS_{Mg} + 0.00071CS_{Ca} ± [168]c’ _{Ba} = −1792pH + 122pH^{2} + 43.8TOC^{2} + 157.7pH × IS − 3.14t × TOC | |||

R^{2} | 0.90 | Residual analysis | |

p | <0.000001 | ||

a | 0.061 | ||

α = arctan (a) | 3.5° | ||

Pearson | 0.28 | ||

c’_{min} (t = 60 °C) | −6741 | ||

c’_{max} (t = 60 °C) | −5524 | ||

c’_{min} (t = 80 °C) | −6898 | ||

c’_{max} (t = 80 °C) | −5527 |

_{Ba}—concentration of barium in leachates; r

_{A}—residual; a—directional coefficient, arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{Ba}, CS

_{Li}, CS

_{Mg}, CS

_{Ca}-Ba, Li, Mg, Ca concentrations in shale sample.

Sr concentration in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Sr} = 11995 − 4001pH + 273.6pH^{2} + 12.1TOC^{2} + 2.2pH × t − 4.8pH × TOC − 7t × IS − 72.4IS × TOC + 40.2G2 + 25.6G5 + 129.1Aw + 1.11CS_{Ba} − 0.1CS_{Mg} − 0.005CS_{Si} + 1.5CS_{Sr} ± [134.6]c’ _{Sr} = −4001pH + 273.6pH^{2} + 12.1TOC^{2} + 2.2pH × t − 4.8pH × TOC − 7t × IS − 72.4IS × TOC | |||

R^{2} | 0.95 | Residual analysis | |

p | <0.000001 | ||

a | 0.046 | ||

α = arctan (a) | 2.6° | ||

Pearson | 0.24 | ||

c’_{min} (t = 60 °C) | −13910 ppb | ||

c’_{max} (t = 60 °C) | −12700 ppb | ||

c’_{min} (t = 80 °C) | −13670 ppb | ||

c’_{max} (t = 80 °C) | −12310 ppb |

_{Sr}—concentration of strontium in leachates; r

_{A}—residual; a-directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{Ba}, CS

_{Li}, CS

_{Mg}, CS

_{Ca}—Ba, Li, Mg, Ca concentrations in shale sample.

Mo concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Mo} = −1002.7 + 37.82t − 15576IS + 207.9TOC + 17.68pH^{2} − 4.05pH × t + 145.83pH × IS − 3.59t × TOC + 166.94IS × TOC + 3.82G4 + 2.41G5 − 0.38CS_{B} + 10.19CS_{Mo} − 0.22CS_{Sr} ± [32.7]c’ _{Mo} = 37.82t − 15576IS + 207.9TOC + 17.68pH^{2} − 4.05pH × t + 145.83pH × IS − 3.59t × TOC + 166.94IS × TOC | |||

R^{2} | 0.91 | Residual analysis | |

p | <0.000001 | ||

a | 0.069 | ||

α = arctan (a) | 4.0° | ||

Pearson | 0.29 | ||

c’_{min} (t = 60 °C) | 1069 | ||

c’_{max} (t = 60 °C) | 1695 | ||

c’_{min} (t = 80 °C) | 1342 | ||

c’_{max} (t = 80 °C) | 1431 |

_{Mo}-concentration of molybdenum in leachates; r

_{A}—residual; a-directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t =80 °C)—explained before Table 5; CS

_{B}, CS

_{Mo}, CS

_{Sr}—Ba, Mo, Sr concentrations in shale sample.

Rb concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Rb} = −77.42 + 1.05t + 462.79 IS + 27.92 pH × IS − 6.49t × IS − 21.88IS × TOC − 0.42G2 + 0.024CS_{Rb} ± [18.71]c’ _{Rb} = 1.05t + 462.79IS + 27.92pH × IS − 6.49t × IS − 21.88IS × TOC | |||

R^{2} | 0.86 | Residual analysis | |

p | <0.000001 | ||

a | 0.102 | ||

α = arctan (a) | 5.8° | ||

Pearson | 0.31 | ||

c’_{min} (t = 60 °C) | 125.9 | ||

c’_{max} (t = 60 °C) | 227.5 | ||

c’_{min} (t = 80 °C) | 80.6 | ||

c’_{max} (t = 80 °C) | 182.2 |

_{Rb}-concentration of rubidium in leachates; r

_{A}—residual; a-directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{Rb},–Rb concentrations in shale sample.

Li concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Li} = 500.56 + 78.85pH + 150.00IS − 7.51pH^{2} + 0.38pH × t − 2.50t × IS − 3.53IS × TOC − 3.03G1 + 1.23G4 − 1.73G5 + 0.41CS_{Li} − 0.0019CS_{Si} + 0.08CS_{Sr} − 0.0018CS_{Ca} ± [10.66]c’ _{Li} = 78.85pH + 150.00IS − 7.51pH^{2} + 0.38pH × t − 2.50t × IS − 3.53IS × TOC | |||

R^{2} | 0.88 | Residual analysis | |

p | <0.000001 | ||

a | 0.082 | ||

α = arctan (a) | 4.7 | ||

Pearson | 0.27 | ||

c’_{min} (t = 60 °C) | 298.8 | ||

c’_{max} (t = 60 °C) | 343.6 | ||

c’_{min} (t = 80 °C) | 341.6 | ||

c’_{max} (t = 80 °C) | 371.4 |

_{Li}-concentration of lithium in leachates; r

_{A}—residual; a-directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{Li}, CS

_{Si}, CS

_{Sr}, CS

_{Ca}–Li, Si, Sr, Ca concentrations in shale sample.

Ca concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Ca} = 1000(3749.56 − 553.95pH − 52.84t + 799.88IS − 83TOC + 39.86TOC^{2} + 7.84pH × t − 322.63IS × TOC − 1.12G2 − 0.05CS_{Ba} − 0.09CS_{Sr} + 0.000553CS_{Ca} ± [27.07])c’ _{Ca} = 1000(−553.95pH − 52.84t + 799.88IS − 83TOC + 39.86TOC^{2} + 7.84pH × t − 322.63IS × TOC) | |||

R^{2} | 0.90 | Residual analysis | |

p | <0.000001 | ||

a | 0.080 | ||

α = arctan (a) | 4.6° | ||

Pearson | 0.29 | ||

c’_{min} (t = 60 °C) | −3897280 | ||

c’_{max} (t = 60 °C) | −3527670 | ||

c’_{min} (t = 80 °C) | −3836130 | ||

c’_{max} (t = 80 °C) | −3172780 |

_{Ca}—concentration of calcium in leachates; r

_{A}—residual; a-directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{Ba}, CS

_{Ca}, CS

_{Sr}-Ba, Ca, Sr concentrations in shale sample.

Mg concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Mg} = −16117 − 8518pH + 1756.39t − 21296IS + 35845TOC + 3511.7TOC^{2} + 30118pH × IS − 726.9t × TOC − 294G2 − 775G3 − 459Aw − 8.2CS_{Ba} + 1.6009CS_{Mg} − 0.1145CS_{Si} ± [2311]c _{Mg} = −8518pH + 1756.39t − 21296IS + 35845TOC + 3511.7TOC^{2} + 30118pH × IS − 726.9t × TOC | |||

R^{2} | 0.92 | Residual analysis | |

p | <0.000001 | ||

a | 0.079 | ||

α = arctan (a) | 4.5° | ||

Pearson | 0.28 | ||

c’_{min} (t = 60 °C) | 26676 | ||

c’_{max} (t = 60 °C) | 57888 | ||

c’_{min} (t = 80 °C) | 30668 | ||

c’_{max} (t = 80 °C) | 92144 |

_{Mg}—concentration of magnesium in leachates; r

_{A}—residual; a-directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{Ba}, CS

_{Mg}, CS

_{Si}-Ba, Mg, Si concentrations in shale sample.

Si concentrations in samples after leaching of A1 to A10 rocks using fluids P1 to P13 | |||

Model | |||

c_{Si} = −298621 + 9229pH − 35067IS − 6556pH^{2} + 457TOC^{2} − 338pH × TOC + 324t × IS − 151.6G1 − 68G5 + 0.0555CS_{Si} ± [2312]c _{Si} = 92297pH − 35067IS − 6556pH^{2} + 457TOC^{2} − 338pH × TOC + 324t × IS | |||

R^{2} | 0.96 | Residual analysis | |

p | <0.000001 | ||

a | 0.049 | ||

α = arctan (a) | 2.8° | ||

Pearson | 0.30 | ||

c’_{min} (t = 60 °C) | 286589 | ||

c’_{max} (t = 60 °C) | 316728 | ||

c’_{min} (t = 80 °C) | 289889 | ||

c’_{max} (t = 80 °C) | 320028 |

_{Si}—concentration of silicon in leachates; r

_{A}-residual; a—directional coefficient; arctan-arcus tangent; Pearson-Pearson correlation coefficient for r

_{A}and c

_{B}; c’

_{min}(t = 60 °C); c’

_{min}(t = 80 °C); c’

_{max}(t = 60 °C); c’

_{max}(t = 80 °C)—explained before Table 5; CS

_{B}, CS

_{Mo}, CS

_{Sr}–Ba, Mo, Sr concentrations in shale sample.

Model | Concentration Operating Range (ppb) | Analysed Concentration Range in MFF (ppb) | ||
---|---|---|---|---|

60 °C | 80 °C | min | max | |

B | 729 | 978 | 371 | 6044 |

Ba | 1217 | 1371 | 25 | 4219 |

Sr | 1210 | 1360 | 125 | 2687 |

Mo | 626 | 89 | 25 | 760 |

Rb | 101.6 | 101.6 | 25 | 249 |

Li | 44.8 | 29.8 | 25 | 186 |

Ca | 369608 | 663354 | 130 | 417450 |

Mg | 31212 | 61476 | 4316 | 38782 |

Si | 30139 | 30139 | 250 | 64153 |

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## Share and Cite

**MDPI and ACS Style**

Rogala, A.; Kucharska, K.; Hupka, J.
Shales Leaching Modelling for Prediction of Flowback Fluid Composition. *Energies* **2019**, *12*, 1404.
https://doi.org/10.3390/en12071404

**AMA Style**

Rogala A, Kucharska K, Hupka J.
Shales Leaching Modelling for Prediction of Flowback Fluid Composition. *Energies*. 2019; 12(7):1404.
https://doi.org/10.3390/en12071404

**Chicago/Turabian Style**

Rogala, Andrzej, Karolina Kucharska, and Jan Hupka.
2019. "Shales Leaching Modelling for Prediction of Flowback Fluid Composition" *Energies* 12, no. 7: 1404.
https://doi.org/10.3390/en12071404