Coating proppant with a surface modification agent (SMA) provides cohesion between grains, resulting in the formation of proppant aggregates. This adhesion has been proven throughout many years of use to provide a variety of benefits, including increasing pack porosity and permeability by hindering compaction, reducing proppant flowback, controlling fines invasion into the proppant pack, and minimizing the migration of fines within the pack. A general review of the contributions to improved and sustained fracture conductivity is provided.
There are two additional, important properties of SMA treatments that have not been previously described in detail. The first of these regards the reduction of gel damage expected with the use of guar-based fracturing fluids. Even when highly effective gel breakers are used, significant conductivity damage is often observed with typical guar-based frac fluids. Data are presented showing that coating proppant with a hydrophobic film significantly reduces the conductivity damage caused by guar-based fluids. Treatment with SMA results in wells that clean up faster with increased productivity.
The second property recently demonstrated is that mineral scaling in the proppant pack is inhibited by coating the proppant with a hydrophobic film of SMA. The scaling can be rapid, caused by water incompatibility of the fracturing fluid with the formation. Geochemical scaling can occur when aluminum-based proppants are used because of incompatibilities between proppant and formation mineralogy. Scaling in the proppant pack is often noted by steeper-than-expected productivity decline curves, ultimately leading to premature refrac treatments. It has been found that coating the proppant surface and the formation face with a strong, hydrophobic film significantly reduces the tendency for mineral scaling to occur in the fracture and extends the life expectancy of a fracture treatment.