Abstract: A method to reduce water influx into a producing well is described comprising the steps of pumping a chemical composition into a production interval and into surrounding formation; said composition being capable of forming, firstly, a physically stabilized structure and, secondly, a chemically stabilized structure, wherein said physically stabilized structure being dissolvable by hydrocarbon containing fluids; letting said composition form said physically stabilized structure within the formation surrounding said production interval; changing pressure condition in said production interval such that the fluid flow within the surrounding formation is reversed; letting thereby in some portions of the formation hydrocarbon containing fluids dissolve said physically stabilized structure and chemically stabilize said structure in the remaining portions by a cross-linking reaction.

Abstract: A water-based drilling fluid (WBM) comprises as additive a reaction product of a polyhydroxyalkane and alkylene oxide. The polyhydroxyalkane is desirably based on a monosacchoride, and is preferably sorbitol. The alkylene oxide may comprise ethylene oxide (EO), propylene oxide (PO) and/or butylene oxide (BO). Good results have been obtained with additives including Sorbitol+18EO, Sorbitol+9PO, Sorbitol+4EO+6BO, Sorbitol+6EO+6BO, or Sorbitol+6BO. Drilling fluids in accordance with the invention have been found in laboratory tests to exhibit improved shale inhibition properties as compared with known polyol containing WBM, particularly in the absence of added potassium ions. This is environmentally advantageous.