Characterization and Evaluation of Gum Arabic Coated Sand as Proppants for Hydraulic Fracturing Applications
Characterization and Evaluation of Gum Arabic Coated Sand as Proppants for Hydraulic Fracturing Applications

Summary/Abstract: Luwa sand was characterized and used to design a proppant for reservoir stimulation/hydraulic fracturing applications. This involves describing the sand in terms of its physicochemical properties, including Sieve analysis, proppant sphericity and roundness measurement, acid solubility measurement, turbidity test, bulk density measurement, proppant crush-resistance test and loss on ignition test (LOI). Additional tests on hardness and elemental (XRF) were also conducted. X-ray fluorescence analysis of the sand indicates that the sand contains higher percentages of Aluminium oxide (Al2O3) than Silicon oxide (SiO2). The hardness test on the Mohs scale confirmed the sand materials as topaz, i.e. not purely corundum (a crystalline form of aluminium oxide) or purely quartz with a hardness value of 8. This value is more complex than silicon oxide, with a hardness value of 7, and less than corundum, with a hardness value of 9. The Luwa sand is uniformly graded; more than 90% of the sand falls within the specified particle range of 20/40 mesh size. The 20/40 mesh-designed proppant shows favourable qualities for consideration as a proppant. However, the sand exhibits low crush resistance at pressures of 3000 psi and, therefore, cannot be applied in reservoirs with closure stress of up to 3000 psi. Because of the low crush strength of Luwa sand, gum Arabic resin was used to coat the sand for improved mechanical and chemical stability. The new resincoated sand was further tested for crush resistance and acid solubility. The result shows a significant improvement in the crush resistance above 3000 psi with less than 5% fines generated. Generally, the uncoated sand produces less than 10% fines at stresses less than 3000 psi and is considered to have a 2 K value, while the resin-coated proppant generates 10% fines above 6000 psi. The resin coated can be classified as having a 5K value and can be applied in reservoirs with closure stress of up to 5000 psi or less.

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