Examining Particle Size Compliance of Total Suspended Solids in Produced Water for Hydraulic Fracturing and Water Injection in the Bakken

The analysis of suspended particle size distribution in produced water for hydraulic fracturing and for water injection operations is vital for the effective development of tight reservoir formations like the Middle Bakken. Several reservoir engineering studies and industry guidelines recommend that particle sizes fall between 1/7th and 1/3rd of the square root of the formation permeability measured in millidarcies, to avoid pore throat clogging and subsequent formation damage. In the tight Bakken formation, with an average permeability of 0.04 millidarcies, the ideal particle size range for total suspended solids should fall within the 0.03 to 0.06 microns range. This study evaluates whether produced water used for hydraulic fracturing and enhanced oil recovery in the Middle Bakken meets this recommendation, as there are no established regulations in North Dakota addressing this issue. Using laser diffraction, particle size distribution was measured in treated and untreated produced water samples. The results show that current treatment methods do not reduce particle sizes to the recommended range. Treated water had particle diameters ranging from 8.5 to 40 μm, while untreated water had diameters ranging from 8.2 to 10 μm. None of the samples met the particle size requirements for safe use in hydraulic fracturing and water injection. This study highlights the inadequacy of current water recycling practices and offers empirical evidence that may guide future regulations on produced water reuse hydraulic fracturing and water injection in the Bakken.