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 Effect of Proppant Failure and Fines Migration on Conductivity of Propped Fractures
J.L. Gidley, SPE, John L. Gidley & Assocs., Inc.; G.S. Penny, SPE, STIM-LAB, Inc.; R.R. McDaniel, SPE, Acme Resin Div. Borden
This report documents a series of tests conducted at Stim-Lab investigating the ability of fines to migrate within various proppant packs. Fluid velocities were equivalent to 10 to 700 BLPD and 0.1 to 1.0 MMSCFD of gas produced from a bi-wing 50-ft fracture height. The study indicates that the critical Reynold's number at which fines become mobile is very low (0.06 for sand proppants, 0.18 for Resin Coated Sand, 0.33 for Light Weight Ceramic proppant). Other findings include:
- The ability of fines to migrate through the proppant pack is dependent both on particle size and on the pore structure of the proppant pack.
- For 20/40 Jordan sand, particles larger than 100 mesh did not migrate within the fracture. These particles were simply too large to travel through the pore throats of the proppant pack.
- Smaller fines in the 100 to 200 mesh range have limited mobility, and are likely to migrate somewhat within the fracture.
- Particles smaller than 200 mesh were observed to travel freely throughout the length of the cell.
- The narrow sieve distribution and higher sphericity of ceramic proppants were shown to “both minimize fines entrapment and prevent the drastic reductions in permeability experienced with … fracturing sands.”
When resin-coated sand tail-ins were examined, a zone of substantially reduced permeability was found where fines bridge at the interface between the sand and resin coated tail-in. Conductivity loss was minimal with 20/40 ceramic tail-in, and there was no observable fines plugging in 16/20 ceramic tail-in. |
