Drilling water wells on Kharyaga oilfield, Timan-Pechora region of Russia, often resulted into poor water production due to aquifer formation plugging with weighting materials and drilled solids and insufficient filter cake removal.

Bentonite-based drilling fluids have been traditionally used for water wells drilling in this area. Bentonite particles invasion into the unconsolidated sand water-bearing horizons is almost impossible to prevent and cure, so in most of the cases actual water production rates achieved proved to be lower than estimated ones. Also, when the wells were put on production considerable sand control related issues often occured. During the drilling phase, when passing through unconsolidated sands, borehole instability problems due to sands washout and hole sloughing have been frequently experienced.

In order to avoid considerable formation damage, borehole instability and increase water production, saturated sized salt drilling fluid system has been proposed for two water wells drilling.

Saturated sized salt drilling fluid has been formulated by water saturation with sodium chloride salt following by treatments with modified sized salt of appropriate grade and additions of alkalinity, filtration, viscosity and foaming control agents. The system showed very stable properties throughout operations with tight LPLT filtration, good thin and smooth filter cake and perfect rheological characteristics. Drilling and coring operations in sand and clay formations have been performed with no problems, neither several days of stand-by had any influence on wellbore stability. Electric logs have shown perfect in-gauge hole.

After the section has been drilled and liner with filter screens has been run to bottom, the filter cake was easily removed by displacing and circulating hole with fresh water to dissolve sized salt particles.

When the water wells were put on production, both of them have shown very good production rates in comparison with other water wells drilled in the field and in comparison with estimated production rates for these two wells also. No signs of sand/fines control related issues have been either experienced during more than two years of water production.

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