Composition for controlling wellbore fluid and gas invasion and method for using same

A slurry composition for controlling wellbore fluid and gas invasion which is initially in a flowable state and, upon undergoing a phase transition, is in a substantially solid state comprising:

• about 70 to 30% by weight of magnesium oxychloride;
• and
• about 70 to 30% by weight of water;
• and wherein
• the composition has a density of about 1.4-1.6 kg/L and a viscosity of about 18-30 cP. when in the flowable state;
• the composition phase transition from the flowable state to the solid state is rapid with formation of little or no gel state;
• and
• the composition has a near-linear relationship between the time required for the phase transition to occur and the composition temperature at which the phase transition occurs.

A method of sealing a wellbore, the wellbore having walls defining a shaft, the method comprising:

• preparing a brine solution comprising an admixture of magnesium chloride salt and water;
• adding about 50 to 30% by weight of magnesium oxide powder to the brine solution;
• agitating the brine solution and magnesium oxide powder to form a slurry;
• placing the slurry into the shaft and along at least a portion of the shaft walls;
• and
• solidifying the slurry along at least a portion of the shaft walls, said solidifying step being characterized by the slurry undergoing a phase transition from a flowable slurry to a substantially solid state in which the phase transition is rapid with formation of little or no gel state and the slurry having a near-linear relationship between the time required for the phase transition to occur and the slurry temperature at which the phase transition occurs;
• whereby a seal is formed along at least a portion of the shaft walls.

A composition for controlling wellbore fluid and gas invasion comprising:

• about 70 to 30% by weight of magnesium oxychloride;
• about 70 to 30% by weight of water;
• and
• about 0.86 to 7.0% by weight of the magnesium oxide of an inhibitor selected from the group consisting of sodium hexametaphosphate, potassium magnesium phosphate hexahydrate and potassium magnesium hexametaphosphate;
• and wherein,
• the composition undergoes a phase transition from a flowable slurry to a solid state in which the phase transition is rapid with formation of little or no gel state;
• and
• the composition has a near-linear relationship between the time required for the phase transition to occur and the composition temperature at which the phase transition occurs.

A composition for controlling wellbore fluid and gas invasion comprising:

• about 70 to 30% by weight of magnesium oxychloride;
• about 70 to 30% by weight of water;
• and
• about 1 to 40% by weight of at least one weighting agent for controlling composition mass, said weighting agent selected from the group consisting of calcium carbonate, barite, galena and mixtures thereof;
• and wherein,
• the composition undergoes a phase transition from a flowable slurry to a solid state in which the phase transition is rapid with formation of little or no gel state;
• and
• the composition has a near-linear relationship between the time required for the phase transition to occur and the composition temperature at which the phase transition occurs.

A method of sealing a wellbore, the wellbore having walls defining a shaft, the method comprising:

• preparing a brine solution comprising an admixture of magnesium chloride salt and water;
• adding about 50 to 30% by weight of magnesium oxide powder to the brine solution;
• agitating the brine solution and magnesium oxide powder to form a slurry;
• during or before the agitating step, the step of adding an inhibitor in an amount of about 0.86 to 7.0% by weight of the magnesium oxide powder to inhibit slurry solidification, said inhibitor selected from the group consisting of sodium hexametaphosphate, potassium magnesium phosphate hexahydrate and potassium magnesium hexametaphosphate;
• placing the slurry into the shaft and along at least a portion of the shaft walls;
• and
• solidifying the slurry along at least a portion of the shaft walls;
• whereby a seal is formed along at least a portion of the shaft walls.

A method of sealing a wellbore, the wellbore having walls defining a shaft, the method comprising:

• preparing a brine solution comprising an admixture of magnesium chloride salt and water;
• adding about 50 to 30% by weight of magnesium oxide powder to the brine solution;
• agitating the brine solution and magnesium oxide powder to form a slurry;
• during or before the agitating step, the step of adding at least one weighting agent in the amount of about 5 to 61% by weight of the slurry to modify slurry mass;
• placing the slurry into the shaft and along at least a portion of the shaft walls;
• and
• solidifying the slurry along at least a portion of the shaft walls, said solidifying step being characterized by the slurry undergoing a phase transition from a flowable slurry to a substantially solid state in which the phase transition is rapid with formation of little or no gel state and the slurry having a near-linear relationship between the time required for the phase transition to occur and the slurry temperature at which the phase transition occurs;
• whereby a seal is formed along at least a portion of the shaft walls.

A method of sealing a wellbore, the wellbore having walls defining a shaft, the method comprising:

• preparing a brine solution comprising an admixture of magnesium chloride salt and water;
• adding about 50 to 30% by weight of magnesium oxide powder to the brine solution;
• agitating the brine solution and magnesium oxide powder to form a slurry;
• during or before the agitating step, the step of adding aluminum sulfate in the amount of about 1 to 10% by weight of the slurry for increasing the rate at which the slurry forms a solid;
• placing the slurry into the shaft and along at least a portion of the shaft walls;
• and
• solidifying the slurry along at least a portion of the shaft walls;
• whereby a seal is formed along at least a portion of the shaft walls.

A method of sealing a wellbore, the wellbore having walls defining a shaft, the method comprising:

• preparing a brine solution comprising an admixture of magnesium chloride salt and water;
• adding about 50 to 30% by weight of magnesium oxide powder to the brine solution;
• agitating the brine solution and magnesium oxide powder to form a slurry;
• during or before the agitating step, the step of adding at least one strengthening agent in the amount of about 1 to 50% by weight of the slurry, said at least one strengthening agent selected from the group consisting of fine silica, coarse silica and mixtures thereof,
• placing the slurry into the shaft and along at least a portion of the shaft walls;
• and
• solidifying the slurry along at least a portion of the shaft walls;
• whereby a seal is formed along at least a portion of the shaft walls.