Erosion by Proppant: A Comparison of the Erosivity of Sand and Ceramic Proppants During Slurry Injection and Flowback of Proppant

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDuring fracture stimulation treatments, particle-laden slurries may damage pumping equipment and have been shown to erode perforation tunnels. During subsequent flowback operations, minor to severe erosion of surface equipment may be observed if formation sand and/or proppants are produced. This paper compares the erosivity of sand-based and ceramic proppants. This paper will examine the erosion mechanisms and demonstrate that theoretical and laboratory measurements are in agreement that low density ceramic proppants, due to the superior roundness and sphericity, are less erosive than more angular sand products.Real-world results from the oilfield, the waterjet industry, pump and valve manufacturers, and the abrasive industry will be reviewed to substantiate the conclusion that proppant angularity is a dominant parameter that increases erosion in typical pumping and flowback conditions. Impingement tests designed to simulate flowback conditions demonstrate that s ubstituting a spherical lightweight ceramic may reduce wellhead or other impingement surface erosion by up to 95% compared to an angular sand. The highest quality frac sand was nine times more erosive than lightweight ceramic (LWC) in impingement studies. Additional studies utilizing intentionally crushed proppant to increase angularity demonstrate that proppant shape is a dominant factor which controls erosion. Surprisingly, flowback testing has shown that resin coatings applied to proppant have the potential to increase erosion by 15-fold. The authors believe this is partially due to a focusing effect attributed to electrostatic charge. Test alterations with multiphase flow have reduced, but not eliminated, this effect.Slurry abrasion testing has shown that the highest quality frac sands are over 250% as abrasive as LWC. Although frac sands are often specified to withstand several thousand pounds of closure stress, significant sand degradation was observed after exposure to a reciprocating five pound weight. Erosivity and abrasivity of all proppant types were shown to increase with proppant damage. Erosion within chokes was found to be three times higher with sand than with lightweight ceramic.Despite conventional wisdom to the contrary, a number of recent laboratory studies have demonstrated that spherical proppants are less likely to flow back from the fracture as compared to more angular products. All data indicate that equipment erosion occurring during the stimulation treatment and subsequent flowback can be substantially reduced through the use of spherical lightweight ceramic proppants.

Erosion-Corrosion of Carbon Steels in a Laboratory: Three-Phase Flow

“…Instead of real fl ow velocities, the nozzle fl ow velocity or a superfi cial fl ow velocity or fl ow rates in a fl ow loop or rotation velocities are used for evaluation. 11,[27][28][29][30][31][32][33] In the present paper, the fl ow velocity distribution between the nozzle and specimen is determined by two different and fully independent methods. To avoid erosioncorrosion in practice one has to know the exact fl ow velocities of the fl uid and the erosive particles at the specifi c point of failure at the metal surface.…”

Successful Field Trial of a Novel Abrasive Jetting Tool Designed to Create Large Diameter-Long Cavities in the Formation to Enhance Stimulation Treatments

“…19 was higher than anticipated because the only available proppant in location to mix with the slurry was intermediate strength ceramic proppant (ISP), which has a 23% higher density than the sand used in experimental lab work. Thus, the higher impact momentum of the denser material, compounded with the inability of the dense particles to turn from the bore of the tool into the nozzle was the likely cause of the higher erosion rate as previously reported by Vincent et al 11 The hardness of the ISP, approaching the tungsten carbide nozzle hardness, may have also contributed to accelerate the nozzle bore erosion 12 . Table 2 provides operational details for each of the abrasive jetting runs.…”

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