A mobile solution captures 99% of entrained oil utilizing an innovative cross-flow method.
Oil entrained in produced water can amount to significant dollars in lost revenue. Extracting oil typically requires and produces significant quantities of water. Even when there are systems in place to separate the oil from the water at the surface, such as “heater treaters” or similar methods, oil is still entrained and lost in the water. When the water gets hauled away, the entrained oil goes with it, along with the revenue the oil could have generated. If you visit a disposal well with an open lagoon, you can see exactly how much oil has separated from the water.
Consider a disposal well that injects 16,000 bbls per day. If the water contains 1,000 ppm of oil, 20 bbls of oil are pumped away every day.
While enough oil separates out to make disposal wells more profitable, there is still enough entrained in the water to cause problems when the mixture is pumped downhole. Revenue is lost and the BHTP (Bottom Hole Treating Pressure) goes up over time as the injection reservoir becomes coated with oil. For example, consider a disposal well that injects 16,000 bbls per day. If the water contains 1,000 ppm of oil, 20 bbls of oil are pumped away every day.
Separating more oil from the water makes sense, but until now it hasn’t been an easy process. There are several separation methods, but dirty produced and flowback water complicate most processes. One proven method is membrane separation. The downside, however, is that it is typically too slow and the membranes are sometimes not robust enough for the oil field. The new micro-porous membrane used in this case study “loves” water and “hates” oil so much that it can be used to dewater a 90 API condensate stream. Water flows freely though the membrane while the oil is held back. The membrane permeates water at much higher rates than traditional oil/water membranes.
SOLUTION AND PERFORMANCE
To fully utilize the membrane, a concept new to the oilfield, known as cross-flow (X-Flow) filtration is required. Instead of dead-end filtration, where the fluid flows directly into the filter, X-Flow continually sweeps the oil-contaminated water across the membrane. Oil-free water permeates the membrane and the membrane is kept clean by the dirty fluid continually flowing tangentially across it. X-Flow extends the life of the membrane to months or years, which eliminates labor-intensive filter change outs.
The pump feeding the dirty, oil-contaminated water does the work that keeps the filter’s surface clean. In dead-end filtration, particles can become embedded in the media. By contrast, this system can be cleaned and backwashed, which greatly extends the life of the membrane. In trials at a disposal well in south Texas, the new filter not only separated oil and water, it also separated bacteria, iron, and more. The resulting salt water was clean and oil free.
The X-Flow filtration equipment can be scaled by adding modules and pumps to get more oil-free, clean water permeate. Currently there are laboratory systems to run 5-gallon samples, a full-scale, field laboratory trailer set up to permeate up to 10 gpm, and one full-scale, field-ready unit to permeate up to 250 gpm. X-Flow modules banked together on a gooseneck trailer can deliver up to 10 bpm of oil-free clean water for disposal or frac fluid reuse.
In summation, this is an economical and innovative technology approach to capture 99 percent of free oil, and it is available now.