Invert-emulsion drilling fluids and methods for reducing lost circulation in a subterranean formation using the invert-emulsion drilling fluids

A method for reducing lost circulation in a subterranean formation during drilling operations, the method comprising:

• introducing an invert-emulsion drilling fluid into the subterranean formation, the invert-emulsion drilling fluid comprising:
• a dispersed aqueous phase comprising an aqueous base fluid;
• a continuous non-aqueous phase comprising a non-aqueous base fluid;
• and
• a first bridging package, wherein:
• the first bridging package consists of one or more particulate carbonate materials;
• all particulate carbonate materials of the invert-emulsion drilling fluid are part of the first bridging package;
• and
• the first bridging package has a trimodal particle size distribution such that the particle size distribution of the first bridging package comprises three peaks, wherein each peak is in the range of less than or equal to 300 microns in the particle size distribution.

An invert-emulsion drilling fluid, comprising:

• a dispersed aqueous phase comprising an aqueous base fluid, wherein the invert-emulsion drilling fluid comprises from 10 wt. % to 30 wt. % of the aqueous base fluid, based on the total weight of the invert-emulsion drilling fluid;
• a continuous non-aqueous phase comprising a non-aqueous base fluid, wherein the invert-emulsion drilling fluid comprises from 20 wt. % to 50 wt. % of the non-aqueous base fluid, based on the total weight of the invert-emulsion drilling fluid;
• from 15 wt. % to 50 wt. % manganese tetroxide (Mn3O4), based on the total weight of the invert-emulsion drilling fluid;
• and
• from 3 wt. % to 12 wt. % of a first bridging package, based on the total weight of the invert-emulsion drilling fluid, having trimodal particle size distribution, wherein:
• particulate carbonate materials having a nominal particle size of from 20 microns to 30 microns define a first portion of particulate carbonate materials;
• particulate carbonate materials having a nominal particle size of from 40 microns to 60 microns define a second portion of particulate carbonate materials;
• particulate carbonate materials having a nominal particle size of from 125 microns to 175 microns define a third portion of particulate carbonate materials;
• and
• the first bridging package comprises at least 35 wt. % of a combination of the first portion of particulate carbonate materials, the second portion of particulate carbonate materials, and the third portion of particulate carbonate materials, based on the total weight of the first bridging package.