| 摘要 |
<p>The invention relates to a wellbore operation, which includes the steps of: (a) introducing into a wellbore a wellbore fluid in the form of a water-in-oil emulsion comprising a dispersed brine phase and comprising as an emulsifier at least one polymer which contains both hydrophilic units and hydrophobic units, at least some of said hydrophilic units containing sulfonate groups, and at least some of said hydrophobic units containing pendant alkyl groups having at least 8 carbon atoms, wherein the sulfonate groups have been introduced into said polymer by first preparing a precursor polymer containing units derived from at least one unsaturated carboxylic acid and/or unsaturated anhydride and then reacting at least a portion of the carboxylic acid and/or anhydride groups of the precursor polymer with a compound of general formula R1 2N(CH2)nSO3X (I) and/or a compound of general formula HO(CH2)nSO3X (II) wherein each R1 is independently selected from hydrogen, methyl or ethyl, X is H, ammonium, or a Group IA metal, and n is an integer of from 1 to 6; (b) allowing a filter-cake to form; and subsequently (c) bringing an aqueous-based fluid into contact with the filter-cake, said aqueous- based fluid having a level of salinity which is lower than the level of salinity of said dispersed brine phase in said wellbore fluid.</p> |
