Wellbore fluid additives, wellbore fluids comprising said additives, and methods of strengthening wellbores using said fluids

A wellbore fluid, comprising:

• an aqueous base fluid;
• one or more weighting agents;
• and
• at least one polymer-based fluid loss additive comprising swellable elastomer particulates,
• wherein wellbore fluid has a density of at least about 9 ppg and no more than about 24 ppg,
• wherein the at least one polymer-based fluid loss additive is at least one latex-based fluid loss additive,
• wherein the at least one latex-based fluid loss additive comprises at least one styrene-butadiene latex, at least one acrylic latex, at least one isoprene latex, at least one styrene vinyl pyrrolidone latex, at least one styrene-acrylic polymer, or a combination thereof, and
• wherein the at least one latex-based fluid loss additive comprises at least one styrene vinyl pyrrolidone latex.