Method of reducing zone permeability by in-situ formation gel of urotropin and urea in an aqueous solution

摘要

Mineral oil is produced from underground mineral oil deposits by injecting one or more flooding media into an injection well and withdrawing mineral oil from a production well. Highly permeable zones are blocked in the region between the injection well and the production well by separately injecting, in succession, two different aqueous formulations, one having water and urotropin and the other having water and urea, through the injection well into the deposit. The two different aqueous formulations mix in the formation after injection to form viscous gels. Either or both formulations have at least one further metal or semimetal compound that can form gels when admixed with bases. The injection well temperature is not more than 60° C.

主权项

1. A process for producing mineral oil from underground mineral oil deposits into which at least one injection well and at least one production well have been sunk, comprising at least the following process steps:
(1) injecting one or more flooding media into at least one injection well and withdrawing mineral oil through at least one production well, (2) blocking highly permeable zones in the mineral oil deposit in the region between the at least one injection well and the at least one production well, by injecting at least one aqueous formulation F1 and at least one aqueous formulation F2 each separately in succession through the at least one injection well into the deposit, the formulations mixing with one another in the formation in a mixing zone after injection to form viscous gels, (3) continuing the injection of one or more flooding media into the injection well, wherein formulation F1 comprises water and urotropin, formulation F2 comprises water and urea, and F1 or F2 comprise at least one further compound M which is selected from the group consisting of metal compounds and semimetal compounds and is able to form gels when admixed with bases, the metal compounds and semimetal compounds being selected from Fe(II) and Fe(III) salts, vanadium salts, zirconium salts, aluminum(III) salts and colloidal silicon compounds, wherein the separate unmixed formulations F1 and F2 cannot form gels even at 50° C., and wherein the concentration of urotropin is at least 1% by weight, the concentration of urea is at least 5.75% by weight and the concentration of the at least one compound M is at least 5% by weight in the mixing zone of the formulations after step (2), based on the sum of water, urotropin, urea and the at least one compound M present in the mixing zone, the injection well temperature before process step (2) being not more than 60° C.