Drilling method using high density, high strength, acid soluble pseudo-crosslinked, lost circulation preventative material

A method of drilling into a subterranean formation comprising:

• introducing into a wellbore passing at least partially through the subterranean formation a cement-forming aqueous fluid having a density greater than 14 pounds per gallon (ppg) (1.7 kg/L) comprising:
• water;
• at least one viscoelastic surfactant (VES);
• at least one monovalent or multivalent salt selected from the group consisting of sodium chloride, potassium chloride, ammonium chloride, sodium bromide, sodium formate, potassium formate, calcium chloride, calcium bromide, magnesium chloride, zinc chloride, zinc bromide, aluminum chloride, and combinations thereof;
• at least one magnesium powder comprising:
• 30-80 wt % MgO, and
• greater than 20 wt % dolomite,
• which magnesium powder works as cement;
• at least one retarder;
• at least one weighting material selected from barium sulfate, micronized barite, hausmannite, ilmenite, manganese tetroxide, hematite, calcium carbonate, magnetite, and combinations of these;
• and
• at least one dispersing agent;
• increasing the viscosity of the cement-forming aqueous fluid by the action of the at least one VES forming elongated micelles;
• where the at least one monovalent salt or multivalent salt is present in an amount effective to pseudo-crosslink the elongated VES micelles to further increase the viscosity of the aqueous fluid;
• forming a cement by reacting the at least one magnesium powder and the water, where the forming of cement is retarded from that which would otherwise occur but for the presence of the retarder;
• and
• inhibiting fluid loss of the fluid into the formation by the combined action of the pseudo-crosslinked VES micelles and the cement.

A method of drilling into a subterranean formation comprising:

• introducing into a wellbore passing at least partially through the subterranean formation a cement-forming aqueous fluid having a density greater than 14 pounds per gallon (ppg) (1.7 kg/L) comprising:
• water;
• at least one viscoelastic surfactant (VES),
• at least one monovalent or multivalent salt selected from the group consisting of sodium chloride, potassium chloride, ammonium chloride, sodium bromide, sodium formate, potassium formate, calcium chloride, calcium bromide, magnesium chloride, zinc chloride, zinc bromide, aluminum chloride, and combinations thereof, where an amount of the at least one monovalent or multivalent salt is from about 0.05 bwoc to above saturation;
• at least one magnesium powder comprising:
• 30-80 wt % MgO, and
• greater than 20 wt % dolomite,
• which magnesium powder works as cement;
• at least one retarder present in an amount from about 0.01 to about 20% bwoc;
• at least one weighting material present in an amount of about 1% to 150% bwoc, where the at least one weighting material is selected from barium sulfate, micronized barite, hausmannite, ilmenite, manganese tetroxide, hematite, calcium carbonate, magnetite, and combinations of these;
• and
• at least one dispersing agent present in an amount of about 0.01% to 2% bwoc;
• increasing the viscosity of the cement-forming aqueous fluid by the action of the at least one VES forming elongated micelles;
• where the at least one monovalent salt or multivalent salt is present in an amount effective to pseudo-crosslink the elongated VES micelles to further increase the viscosity of the aqueous fluid;
• forming a cement by reacting the at least one magnesium powder and the water, where the forming of cement is retarded from that which would otherwise occur but for the presence of the retarder;
• and
• inhibiting fluid loss of the fluid into the formation by the combined action of the pseudo-crosslinked VES micelles and the cement.