Coated Fracking Proppants


 Number/Link: WO2017/213855

Applicant/Assignee:  Dow

Publication date: 14 December 2017

Gist”: Proppant particles are coated with polyamide based on isocyanate and carboxylic acids

Why it is interesting: Proppant particles are used in the hydraulic fracturing process to force open rock fissures to extract gas and oil – as discussed before in this blog. According to this invention the proppant particles are coated with a reacting mixture of a polyisocyanate (e.g. polymeric MDI) and polycarboxilic acids (e.g. a blend of citric acid and an acid-terminated polyether triol). Under the high pressure and temperature of the fracture, the coating will bond the proppant particles together, thus preventing flow-back of the proppant and the blocking of the well. The coating can contain additives to capture heavy metals like radium and sulfides like hydrogensulfide to reduce contamination of the fracture fluid.


Citric acid

Polyurethane Coating for Frac Tanks


 Number/Link:  WO2015/050811

Applicant/Assignee: Dow

Publication date: 9-04-2015

Gist”: Use of butylene oxide polyols in sprayable coating composition

Why it is interesting: The hydraulic fracturing fluids used in ‘fracking’ operations are stored and transported in so-called ‘frac tanks’. Because fracking fluids can contain highly corrosive compounds such as HCl and solvents such as toluene and xylene, the tanks need a protective coating with a high chemical resistance. According to this application such a coating can be accomplished using a sprayable 2 component system comprising polyols with a high butylene oxide (BO) content, e.g. polyols prepared from 80% butylene oxide and 20% propylene oxide (PO) with a molecular weight of about 2000 and a functionality of 2. In the first component the BO/PO polyol is prepolymerized with an isocyanate e.g. MDI, while used as such in the second component. The two components are prepared such that they both show a similar viscosity of less than 1500 cP at 25°C, so that the coating composition is sprayable.

Frac tank.

Frac tank.