Total Phosphorus Recovery in Flowback Fluids After Gelled Hydrocarbon Fracturing Fluid Treatments

摘要

A previous work described refinery plugging caused by volatile phosphorus components originating from phosphate ester oil gellants. Also documented were two successful field trials of new phosphonate ester oil gellants shown to address this problem. Another paper presented the results of additional field testing of phosphonate ester gellants directed at the optimization of cost and performance. A maximum of 0.5 ppm volatile phosphorus in crude specification has been proposed to address costly unplanned refinery shutdowns. This specification is based on what is considered achievable through a combination of new chemistry and typical field dilution. However, this specification is based on average concentrations of phosphorus added to the oil to gel it and assumes the oil is phosphorus free to begin with. In some flowback studies, total and resulting volatile phosphorus concentrations greatly in excess of that added have been observed. In addition, refinery plugging is more the result of total phosphorus throughput than peak concentrations at any one point. Therefore, an understanding of total phosphorus recovery in addition to peak concentrations is needed. The objectives of this paper are to study: 1. Total percent recovery of phosphorus originally added as phosphorus based gellant; 2. Total percent recovery of volatile phosphorus as a function of total phosphorus; 3. Peak concentrations of total and volatile phosphorus; 4. Phosphorus concentrations in new and reused fracturing fluids before the addition of gellants; and, 5. Potential explanations for phosphorus concentrations significantly higher than those originally added, which include phosphorus removal resulting in a positiveegative initial mass balance and long-term phosphorus removal with respect to overall mass balance.