Self-crosslinking polymers and platelets for wellbore strengthening

A wellbore fluid comprising:

• an invert emulsion fluid comprising a mixture of a non-oleaginous fluid of a non-oleaginous internal phase and an oleaginous fluid of an oleaginous external phase;
• at least one two-dimensional platelet-like material comprising particles having an average thickness from about 1 to 20 nanometers, a diameter from about 1 to 50 microns, and an average surface area from about 10 to 1000 m2/g;
• and
• at least one mineral fiber additive selected from a powdered cellulose-based fiber material,
• wherein
• the non-oleaginous fluid of the non-oleaginous internal phase comprises a mixture of a first latex-containing polymer and a second latex only polymer,
• the first latex-containing polymer comprises at least one copolymer formed from at least one natural polymer and at least one latex monomer,
• the second latex only polymer is distinct from the first latex-containing polymer,
• the first latex-containing polymer is selected from a starch styrene-butadiene copolymer;
• the at least one mineral fiber additive further comprises fibers of a natural mineral fiber material having fiber lengths from about 0.1 mm to about 20 mm and fiber diameters from about 5 microns to about 15 microns,
• fibers of the powdered cellulose-based fiber material have fiber lengths from about 8 microns to 2000 microns, and
• the wellbore fluid has a density that is less than about 24 pounds per gallon.