Polyurethane for Oil Well Refracking

Patent Title: METHODS AND MATERIALS FOR REFRACTURING A PARTIALLY DEPLETED OIL AND GAS WELL

Number/Link: US2018/0346786

Applicant/Assignee:  Covestro

Publication Date: 6 December 2018

“Gist”: Use of low-reactive, low-viscosity PU systems for oil well sealing

Why it is interesting: It is known that partially depleted fracking wells can be “re-fractured” to increase production. Prior to this operation former perforations in the well casing need to be sealed to prevent furthering of existing fractures, by using a chemical “diverting agent”.  According to this invention, the diverting agent can be a polyurethane system with a long potlife and relatively low viscosity, which is prepared from an unblocked hexamethylene diisocyanate and a polypropyleneoxide triol which is miscible with the isocyanate. In the examples an allophanate-modified HDI is used together with a 450-molecular weight PO triol and a delayed-action tert amine catalyst. The system does not de-mix and has a gel time ranging from 30 to more than 1000 minutes.

refracking

Sealing of fracking well

 

 

Coated Fracking Proppants

Patent Title: AMIDE BASED COATING

 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.

citricacid

Citric acid