Compatibility Guar and FR

Compatibility with Slick Water FR Hydrolyzed Anionic Polyacrylamide Friction Reducer in 40% Produced Water @0.5 gpt, pH 5.7-6.0

ClO2 Treated Produced Water FR Flow Loop Testing

•  ClO2 Dose to 31.5 ppm – No Impact on FR

•  Chlorite Dose to 125 ppm – No Impact on FR

•  Greater impact on FR due to pH depression

No Impact On Friction Reducer

Produced Water Oxidation & Separation

Iron Sulfide Treatment

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Compatibility with Borate Cross-linked Guar - Testing

•  Testing determined the impact of both chlorite ion (20, 200 and 2000 ppm as ClO2

-) and ClO2 (5 and 50 ppm) residuals on guar hydration and on viscosity development as measured by vortex closure time.

•  Independence Oilfield Chemical guar (LFC G4 @ 0.48 wt%) hydration and vortex closure at a fixed borate cross-linker (XLM-B2) concentration were evaluated throughout this study.

•  The effect of pH on hydration rate was also examined. It is important to understand and control the impact of pH when disinfecting water with ClO2. Oxidation of various species can lower pH, which will not affect hydration but may impact vortex closure if sufficient pH buffer is not added to raise pH to 9.

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Compatibility with Borate Cross-linked Guar - Hydration

Hydration:

•  The presence of chlorite ion at 2000 ppm did not affect hydration (Figure 1).

•  Hydration was also not affected by 5 ppm residual ClO2.

•  Below pH 8, hydration was only slightly affected by 50 ppm residual ClO2 (Figure 2).

•  However above pH 8, 50 ppm ClO2 had much more significant impact on hydration. (Therefore if high residuals are expected, it’s preferable to add buffer after hydration.)

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Compatibility with Borate Cross-linked Guar - Residual

Residual ClO2 & Chlorite:

•  At a 5 ppm dose, the ClO2 residual is completely consumed by the reaction with guar within 2.5 minutes over the pH range of 5-10.

•  At a 50 ppm dose, 30-40 ppm of ClO2 residual is consumed within 2.5 minutes, the extent of which is pH dependent. At this dose approximately 5 ppm ClO2 residual can be measured after 15 minutes.

•  In all cases, residual chlorite is measured, indicative of one-electron oxidation by ClO2. Chlorite residual is available for further oxidation (Figures 3 & 4).

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Compatibility with Borate Cross-linked Guar – Vortex Closure Vortex Closure:

•  With no ClO2 or chlorite added, in pH 8 buffer, guar closed vortex at 256 seconds.

•  With 5 and 50 ppm ClO2 residuals at this pH, the vortex is not closed within 30 minutes.

•  However, in pH 9 and 10 buffers, vortex closed rapidly (43-62 seconds) regardless of ClO2 or chlorite concentration (Figure 5).

Conclusions: •  Disinfection control is important from both safety

and performance perspective. •  ClO2 residuals are typically under 5 ppm •  Chlorite residuals are typically under 50 ppm •  At these levels guar hydration is unaffected

•  At these levels guar vortex closure is unaffected above pH 9; below pH 9 closure is significantly affected.

•  50 ppm ClO2 residual below pH 8 marginally affects hydration; above pH 8 significantly affects hydration

•  2000 ppm chlorite does not affect either hydration or vortex closure.

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Compatibility Guar and FR

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