A series of laboratory experiments have been conducted with specially designed equipment to aid in quantifying the pressure drop of proppant-laden slurries while flowing between coal, and measuring the conductivity of various proppants once placed in a coal fracture.
The rheology and proppant transport of borate-crosslinked fluids with and without proppant has been evaluated in a slot with walls cast from the surfaces of fractured coal, in an effort to quantify the impact of tortuous coal fractures on the pressure drop down the fracture. A second device has been constructed to view the flow of slurries through cleats of various sizes. Data is presented on the measurement of pressure increases due to bridging vs cleat size, proppant size, concentration and rate.
The long-term conductivity and permeability of various sands have been measured between fractured Fruitland Coal. Predictive equations have been developed to predict permeability between coal vs sand sieve size, and predict loss of permeability due to embedment. Non-Darcy flow factors and constants are presented for calculating non-Darcy flow vs sand type and size between coal.