Abstract

Over the past decade, chemical providers in North America’s unconventional production basins have been refining their understanding of the challenges that operators face. The unique brine chemistries found in some of the unconventional basins, such as the Bakken/Three Forks, Marcellus/Utica, and Bone Springs formations, provide operators and chemical providers challenges that can be addressed when proper steps are taken. For instance, the proper selection of a frac fluid source water can be a critical decision in alleviating early well life scale challenges. High concentrations of calcium and/or barium mean even low levels of bicarbonate and/or sulfate are more of a risk than in other basins. The presence of iron alters which scale inhibitors are most effective. These conditions have impacted chemical selection in scale, corrosion, H2S and O2 scavenger product lines, in addition to their specific applications as well as considerations for disposal. In addition to product selection, new applications have been pioneered in North America to effectively mitigate challenges associated with carbonate and FeS scales in the unpredictable horizontal sections of unconventional wells. As more data is collected from Vaca Muerta, the similarity of brine chemistries from the Bakken/Three Forks, Marcellus/Utica, and Bone Springs formations (with high salinity, calcium, barium, and iron concentrations) becomes more evident.

Based upon similarities in scale modeling and performance test results, it is possible to take the lessons learned in certain North America unconventional production basins and apply these lessons in Vaca Muerta production chemical selection processes. The results of scale modeling and performance testing from North American basins and the correlation to field results will be discussed.

Scale modeling and field results suggest the high calcium carbonate and/or barium sulfate scaling risks associated with potential frac waters used to frac Vaca Muerta wells. Performance testing of scale inhibitors including anaerobic dynamic scale loop and anaerobic static bottle tests has identified the most effective scale inhibitor products to use in Vaca Muerta brines. These products have already been effectively applied in Vaca Muerta production systems.

These case histories highlight how proper considerations and product testing have led to highly effective programs. Other selection criteria that are discussed include (a) critical ion measurements in Vaca Muerta produced brine, (b) decisions to be made in freshwater selection for fracking and product applications (c) monitoring best practices and (d) disposal of produced fluids and production chemical byproducts.

These lessons learned can show how decisions made by well completion teams can impact future decisions made by production teams and ultimately by the disposal teams. If these guidelines are considered, then the Vaca Muerta field operators can quickly optimize chemical programs while not rediscovering lessons already learned over the past decade in North America.

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