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During several decades high viscous guar-based gels remained main and single fluid type on Russian fracturing market. Having high viscosity and excellent proppant carrying capacity, crosslinked gel possesses damaging nature–it results in low retained conductivity of proppant pack even in case of oxidative destructors usage ( In 2016-2017 low viscosity fluids based on synthetic polymer – polyacrylamide (High Viscosity Friction reducer, HiVis FR, HVFR, Viscous slickwater) started to be actively used in North America for shale fracturing. Along with improved sand carrying capacity in comparison with conventional FR due to its elastic properties, fluid demonstrated high retained conductivity of sand packs (~80%) confirmed during laboratory investigations, firstly performed by Stim-Lab (Stim-Lab Proppant Consortium 2015 – Fracturing Fluid Cleanup of various Low Polymer Fluid Systems; Stim-Lab Proppant Consortium - 2016 – Historical and current Friction Reducer Studies). However, fracturing design and job execution on conventional sandstones in Russia significantly differs from shales stimulations, i.e. serious work was required in order to start implementation of HiVis FR (Viscous slickwater) on sandstones in Russia. First field trials of Viscous slickwater were performed in Russia in the end of 2018 on conventional sandstones owned by "Gazpromneft-Khantos" - Gazpromneft subsidiary. In spring 2019 first time in the world full scale fracturing jobs, where Viscous slickwater with only ~30 cP at 511 s-1 demonstrated high transport efficiency to carry and place ceramic proppant at moderate rates (4-4.5 m3/min), as in combination with crosslinked gel as well as single fracturing fluid. Prior HiVis FR was qualified for application on sandstones as alternative to guar-based high viscous gels, major laboratory investigations were performed on novel fluid rheology, dynamic proppant transport, mechanical fluid properties, influence of breakers, etc (Loginov at al. 2019). Later, in field trials phase, additional laboratory testing was carried out to address specific fluid performance questions. New technology field trials for "Gazpromneft-Khantos" were executed with high operational success–according to initial fracturing design. Viscous slickwater was pumped as single fracturing fluid, as well in combination with crosslinked guar gels (≥50%). Jobs were performed on vertical, inclined and horizontal wells. Despitê20 fold difference in viscosity, high proppant transport efficiency of HiVis FR allowed to place standard for South part of Priobskoe oilfield designs in case of hybrids and slightly less aggressive designs in case of 100% jobs on slickwater. Application of Viscous slickwater allowed to identify number of advantages of novel fluid over traditional guar-based fluids both in terms of operational efficiency, location and environmental footprint and fluid performance characteristics. It was shown that start production of wells treated with slickwater were ~10-20% higher, and current production rate were comparable in comparison with traditional designs with higher proppant volume. Field trials on implementation of Viscous slickwater - fluids based on polyacrylamide on low viscosity reservoirs owned by "Gazpromneft Khantos" were proven to be successful both from operational and technological point of view and have become a new milestone in history of Russian fracturing. This basis could be key to the future effective development of analogical oilfields in the world. |
