METHOD FOR MUDDING FORMATION REMOVING FROM HYDROCARBON CONTAINING FORMATIONS Russian patent published in 2006 - IPC E21B43/27 

FIELD: oil and gas industry, particularly to remove clay-and-polymeric mudding formations from hydrocarbon containing formations, for oil and gas well repair to increase output.

SUBSTANCE: method involves injecting technological solution into formation; holding the solution in the formation for 6-20 hours to provide reaction and removing the technological solution. The technological solution comprises ammonium fluoride in amount of 10-20% by weight, potassium hydroxide in amount of 6-8% by weight, surfactant in amount of 0.2-1.5 % by weight, remainder is water. Technological solution volume is 1-1.2 mudded zone volumes. After reaction termination the second technological solution may be injected into the formation. The second technological solution may comprise sodium bisulfate or ammonium persulphate in amount of 5-12 % by weight, surfactant in amount of 0.2-1.5 % by weight, remainder is water. Volume of the second technological solution is equal to 1-1.2 mudded zone volumes. Then well is drained for 8-12 hours by performing 10-14 depression-repression cycles and well is developed. In the case of gas well treatment 50-70% methanol is injected in the formation before technological solution injection. Methanol is taken in amount of not less than 2 volumes of technological solution. In the case of calcium carbonates presence in the formation the formation is decarbonized for 4-6 hours with the use of 5-12% aqueous sodium bisulphate solution taken in amount equal or more than pore volume of zone to be treated.

EFFECT: possibility to recover hydrocarbon containing formation reservoir permeability by removing polymeric mudding formations.

4 cl, 1 ex, 2 tbl