Summary

Microbial activity in raw repurposed waters from Permian operations is known to cause enhanced corrosion and downhole fouling in the reservoir if left un-treated. For this reason, mobile treatment units have been employed to treat raw production waters. However, stability of treated water during storage has not yet been explored due to difficulty in obtaining timely and accurate microbial levels. This paper addresses rapid, economic, field ready technology that can be used to determine treated water stability. Preliminary research compiled raw produced water data from GPRI field test data from work with two Permian Basin shale operators. Data was used to select chemical and biological testing parameters of interest. Treated and un-treated production water, from salt water disposal wells (SWD), was monitored throughout three seven hour, two-stage filtration runs. Sample analysis was carried out immediately after sampling to achieve real-time analysis. HACH benchtop analysis, and Mycometer's Bactiquant meter were used to determine select chemical specie concentrations and microbial biomass levels. Remaining water quality analysis was carried out by commercial laboratory. Using a two-stage filtration scheme, a significant reduction of divalent ion species and biological activity is observed in permeate waters. Monovalent species were not directly affected by filtration treatment. Metabolically active monovalent ions including: nitrate, ammonia, ammonium and nitrite are reduced by microbial activity in permeate during temporary storage. Additional metabolically active ions including: soluble iron, sulfate, manganese, and dissolved organic carbon were reduced by filtration treatment. Concluding the study, our findings show that treated produced water still exhibits an unstable, nutrient rich nature capable of supporting microbial growth and redox activity during storage. Therefore, without the addition of a biocide to establish a residual concentration, microbial biomass levels can be expected to regrow surprisingly fast after any removal treatment.

Introduction

Growing concerns about water have forced many industries to re-evaluate their water usage. Drought conditions in areas with growing populations and low levels of aquifer recharge is building concern about the environmental sustainability of these areas (Lyons et al., 2014). Because of this, companies have begun promoting produced water re-use and the use of brackish water. Eagle Ford producers have begun using approximately 20% brackish water, and Permian Basin operators reportedly utilize 30% brackish water (Lyons et al., 2014).

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