COMPOSITION FOR CONTROLLING WELLBORE FLUID AND GAS INVASION AND METHOD FOR USING SAME

The disclosure is directed to a composition for controlling wellbore fluid and gas invasion including methods for using said composition. The composition of the invention is a flowable slurry preferably comprising about 70 to 30 % by weight of magnesium oxychloride and about 70 to 30 % by weight of water. The composition is a flowable slurry at composition temperatures below about 60 °C and sets to form a substantially solid mass upon reaching a composition temperature of about 60-68 °C. The phase transition is rapid, thereby limiting or avoiding formation of gel states which contribute to incomplete wellbore seals. The rapid set of the slurry further avoids invasive contamination of earthen formations surrounding the wellbore. 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. This advantageous property permits the composition set time to be accurately determined and modified as required through the addition of accelerators and inhibitors. The phase transition occurs predictably at high pressures typical of those encountered in wellbore operations. Additives may be included to modify the properties of the composition. The method includes use of the composition to control the loss of fluids and gases from the wellbore.