A new laboratory procedure that makes hydraulic fracturing more effective has been granted a U.S. patent.
Saudi Aramco on May 11 was granted U.S. Patent 7,712,525 for "Determination of Well Shut-in Time for Curing Resin Coated Proppant Particles," developed by Hazim Abass, Mohamed Alqam, Mirajuddin Khan and Abdulrahman Mulhem of the EXPEC Advanced Research Center (EXPEC ARC).
When an oil or gas well is not producing to expectations, petroleum engineers usually apply stimulation techniques to improve productivity. One of those methods is hydraulic fracturing, in which a viscous fluid is injected at a high rate into the well. That causes fractures deep in the reservoir rock.
When injection stops, the new fractures tend to close. That is why propping particles, synthetic rock particles named proppants, are used to keep the fractures open throughout the life of the well.
Some proppant particles are coated with resin to keep them glued together in the fracture so they won't flow back when the well is in production. During injection, the large volume of cold injection fluid decreases reservoir temperature, but the resin requires a certain temperature to fuse the proppant particles together. To ensure the right temperature, the well must be closed to let the temperature down in the well increase.
Until the invention, the industry did not have a way to test how long a well must be closed to keep the proppant from flowing back.
Enter Saudi Aramco, which developed the new laboratory method to solve that problem. The method subjects resin-coated proppants in the laboratory to the temperature and pressure conditions downhole.
A sample is loaded in a system in which sound is used to test the proppant's properties under constant pressure but increasing temperature. The results tell the testers how much shut-down time is required for the downhole temperature to reach the optimum level.
Saudi Aramco field engineers have adopted the method and have successfully prevented losses due to proppant flowback.
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