Urea-aldehyde sealing agents and method of making the same

Claim 1

METHOD OF PREPARING A SEALING AGENT FOR SEALING POROUS FORMATIONS WHICH COMPRISES REACTING UREA WITH A REACTANT SELECTED FROM THE GROUP CONSISTING OF FORMALIN AND FURFURAL UNDER CONDENSATION CONDITIONS TO FORM A THERMOSETTING RESIN, THE WEIGHT PROPORTION OF URA TO THE SECOND-NAMED REACTANT BEING WITHIN THE RANGE OF ONE OT 1 1/2-2 1/2 WHEN SAID SECOND-NAMED REACTANT IS FORMALIN AND ONE TO 1-6 WHEN SAID SECONDNAMED REACTANT ID FURFURAL; CONTINUING THE REACTION UNTIL THE RESIN HAS REACHED AN INTERMEDIATE PLASTIC SOLID STAGE AT WHICH IT IS, WHEN SAID SECOND-NAMED REACTANT IS FORMALIN, A DISTINGUISHABLE MASS IN THE REACTION MIXTURE AND IS DISPERSIBLE BY STIRRING IN WATER WITHOUT THE AID OF AN EMULSIFYING AGENT TO FORM A NON-COLLOIDAL THE REACTION WHEN SAID INTERMEDIATE PLASTIC SOLID SUSPENSION STABLE FOR AT LEST FIVE HOURS; STOPPING THE REACTION WHEN SAID INTERMEDIATE PLASTIC SOLID CONDENSED RESIN CAPABLE OF FURTHER CONDENSATION TO A HARD INFUSIBLE STAGE UPON APPLICATION OF HEAT; AND DISPERSING THE RESIN IN WATER THEREBY FORMING, AS THE DESIRED PRODUCT, A NON-COLLOIDAL AQUEOUS SUSPENSION WHICH, WHEN FORCED INTO A BED OF 10 MESH SAND, WILL FORM A RESIN SHEATH AT THE FACE OF THE BED CAPABLE OF THERMOSETTING TO A HARD LAYER NON-POROUS TO DRILLING FLUID.