Maintaining shale stability by pore plugging

An additive composition for aqueous drilling fluids which imparts improved stability when used in drilling shale formations comprising:

• an aqueous phase comprising an effective quantity of one or more nanoparticles comprising a size range of between 5 and 500 nanometer and adapted for use in a hydrocarbon bearing shale formation selected from Pierre, Arco China, C1, C2, C3, C4, C5, Atoka, Gumbo, Pierre, Wolfcamp, Wellington or Mancos, wherein the one or more nanoparticles are between about 5 and about 45 weight percent nanoparticles and are selected from silica, aluminum, iron, titanium or other metal oxides and hydroxides wherein the nanoparticles decrease swelling and plug pore throats.

An aqueous well-drilling fluid for hydrocarbon bearing shale formation selected from Pierre, Arco China, C1, C2, C3, C4, C5, Atoka, Gumbo, Pierre, Wolfcamp, Wellington or Mancos containing between about 1 and about 50 weight percent of a silica nanoparticles, wherein the nanoparticles are selected from silica, aluminum, iron, titanium or other metal oxides and hydroxides and the silica nanoparticles comprise between about 5 and about 45 weight percent nanoparticles in a size range of between a 5 and a 500 nanometer range and are adapted for use in shale selected from Pierre, Arco China, C1, C2, C3, C4, C5, Atoka, Gumbo, Pierre, Wolfcamp, Wellington or Mancos.

An aqueous well-drilling fluid containing

• an aqueous well-drilling fluid adapted for use in shale selected from Pierre, Arco China, C1, C2, C3, C4, C5, Atoka, Gumbo, Pierre, Wolfcamp, Wellington or Mancos;
• wherein the aqueous well-drilling fluid comprises an aqueous phase and between about 5 and about 45 weight percent silica nanoparticles with a particle size of between 5 and 500 nm.

A method of increasing shale formation stability with a water-based drilling fluid, the method comprising:

• identifying a shale formation selected from Pierre, Arco China, C1, C2, C3, C4, C5, Atoka, Gumbo, Pierre, Wolfcamp, Wellington or Mancos;
• delivering the water-based drilling fluid to the shale formation, wherein the drilling fluid comprises an aqueous continuous phase and a slug of nanoparticles between about 5 and about 45 weight percent nanoparticles and with a particle size of between 10 and 500 nm, wherein the nanoparticles are present in a sufficient weight percent to stabilize the shale formation.