Water Management Approach for Shale Operations in North America

Abstract

This paper discusses technical drivers that influence the produced/flowback water management goals and decisions in unconventional hydrocarbon developments and then presents case studies and a decision tree chart for effective water treatment. Produced/flowback water quality in shale projects is influenced not only by the formation, but also by the fracturing fluid introduced to the formation during hydraulic stimulation. The water produced by shale wells can contain suspended solids, dissolved solids, organics including hydrocarbons and residual fracturing fluid chemicals, and bacteria. Furthermore the water composition can change rapidly during the short flowback period followed by gradual stabilization during the production phase. The clean-up treatment of water with complex and highly varying quality with an effective and robust treatment process presents specific challenges. Conventional oilfield water treatment technologies may not be always effective in unconventional gas projects due to specific constituents in produced/flowback water such as residual polymers. This paper describes the functional water treatment steps, which target the most common removal of suspended solids and oil/condensate from flowback water/produced water for recycling or disposal operations. In addition pilot tests were run to validate and assess the performance of solids and oil/condensate removal processes. One key learning is that residual guar gum polymer in the water has a major impact on treatment effectiveness and thus the equipment selection process.

On the cost of electrodialysis for the desalination of high salinity feeds

“…Direct reuse, whereby produced water is directly blended with freshwater before formulation of the fracturing fluid, results, by and large, in the lowest treatment costs but greater chemical costs for fluid formulation and perhaps a decline in the well's production. Increased costs associated with reuse, depending on the degree of treatment employed, can come in the form of: increased friction reducer and scale inhibitor demand with high chloride contents; increased scaling within the shale formation with the presence of divalent ions; increased corrosion of pipes; increased levels of sulphate reducing bacteria resulting in the production of H 2 S gas [8]; and a reduction in the performance of coagulation/flocculation, flotation, gravity settling and plate and frame dewatering equipment due to residual unbroken polymer gel [9].…”

“…Many of the challenges faced in reuse can be dealt with through primary treatment that removes suspended solids, oil, iron, unbroken polymers and bacteria [9], generally at a cost much below complete desalination (circa $1/bbl ($6.3/m 3 ) compared to $3.50-6.25/bbl ($22-39/m 3 ) for complete desalination [1]). The need for the removal of all solids, suspended and dissolved, is less clear.…”

“…Depending on the fracturing fluid desired, chemical use can be significant. Fedotov et al [9] indicated that the use of drag reducing In place of a distillation process, we propose the use of electrodialysis desalination to partially desalt produced water. The objective is to achieve a configuration that can reduce water treatment costs relative to distillation, by avoiding complete desalination, but can provide the benefit of reduced total dissolved solids relative to a direct reuse configuration.…”

Practical insights into liquid loading within hydraulic fractures and potential unconventional gas reservoir optimization strategies

“…Water management and its impact on unconventional reservoir economics is a key focus area for the industry these days. Slutz et al (2012), Fedotov et al (2013) have highlighted the issues at hand and suggested possible best practices. On an average less than 25% of stimulation water is ever recovered back in most of the contemporary unconventional reservoirs under development (Pagels et al, 2012).…”