Resin coated proppants are widely used in fracturing applications. They serve two purposes namely to increase the strength of proppant material to withstand closure stresses and to mitigate any proppant flowback. Typically, resins used for proppant coatings are made up of hydrophobic polymers and are inherently incompatible with the aqueous fracturing fluid. To avoid any slugging issues due to this incompatibility, the coated resins are typically semi-cured. The coating process needs to be undertaken during proppant manufacturing and adds to the overall cost of the proppants used.
In this paper we showcase the development of novel insitu generated hybrid materials that enhance the proppant strength. Moreover, the resins used for proppant coating are introduced as a water external emulsion, thus making them compatible with the aqueous fracturing fluids. We show that by using a solid resin based emulsion system as proppant coating material we could introduce this system on-the-fly along with the fracturing fluid without facing any incompatibility issues between the hydrophobic resin and the aqueous fracturing fluid. We further show that by using tactoid based filler materials suspended with the emulsified resin we could tremendously enhance the overall mechanical strength of the proppants. The solid resin above the temperatures of 60°C melts and starts to intercalate into the layered tactoid fillers. The process of intercalation is driven by mechanical shear as the fracturing fluid is pumped downhole, as well as by thermodynamics of intercalation. Specific structural modifications were utilized to increase the entropy of the layered tactoids, facilitating the intercalation of resin. Increased intercalation of the resin inside confined spaces of the tactoid overcame the Van der Waals forces that hold the tactoid layers together. As the tactoid layers separated they formed an exfoliated structure of high aspect ratio filler with nanoscale dimensions of around 1nm thickness. The high aspect ratio nanofillers uniformly dispersed in the resin matrix ensured effective load transfer from the matrix thereby tremendous increase in the overall mechanical strength of the resin coated proppants.
We studied the mechanical properties by evaluating the compression strength of the resin nanocomposite coated proppants in comparison with the pristine resin coated and uncoated proppants. The mechanical strength enhancements in the nanocomposite coated proppants were clearly evident from this study. Structural evaluation of nanocomposites showed uniform dispersion of the fillers in epoxy matrix could be achieved whilst generating the nanofillers insitu. The viscoelastic properties of the nanocomposite based coating were also investigated and showed better mechanical behavior over those of pristine resin coatings.
Novelty of this paper of newly developed proppant coating nanocomposite material is in situ generation of the nano fillers and on the fly deployment of the resin coating material along with fracturing fluid due to enhanced compatibility.