Nitrogen-gas-stabilized cement and a process for making and using it

In a well treating process in which an aqueous slurry of cement is pumped into a well to form a substantially impermeable set cement within a subterranean zone in which the temperature and pressure are relatively high, the improvement comprising using as said slurry:

• an aqueous liquid slurry of cement which sets to form an integral body of set and hardened cement at said relatively high temperature and pressure;
• dissolved within the aqueous liquid phase of said slurry, reactants which react to form nitrogen gas while they are so dissolved;
• and
• the concentration of said reactants within said liquid, and the amount of gas which can be generated by said reactants, and the rate at which said reactants react at said selected temperature, being such that when the reactant-containing cement slurry is allowed to set at said relatively high temperature while it fills a portion of a rigid walled tube and is contacted by an externally pressurized gas having said relatively high pressure, the pressure and volume of the gas generated by said reactants prevents any significant shrinkage by the cement or any significant leakage of the externally pressurized gas past the set cement.

A process for compounding an aqueous slurry of hydraulic cement and setting the cement within a zone into which the slurry is flowed and within which the pressure and temperature are high relative to those in which the slurry is compouned, comprising:

• compounding a pumpable aqueous slurry of hydraulic cement which is capable of being flowed into and set within the zone to be cemented;
• dissolving within the aqueous liquid phase of the slurry reactant compounds which are capable of reacting while dissolved in that liquid and react to produce nitrogen gas and by-products which are substantially inert to the components of the slurry and the setting of the cement;
• correlating the concentration of the reactants within the slurry as a whole with the pressure and temperature in the zone to be cemented so that the volume of the gas which the reactants produce, while reacting under those conditions, substantially equals the volume loss which the slurry undergoes while the cement is setting under those conditions;
• correlating the rate of reaction of the reactants and the initial concentration of the reactants within the aqueous liquid phase of the slurry with the temperature in the zone to be cemented so that, at that temperature and concentration, the amount of gas the reactants will produce before the cement becomes initially set at that temperature is significantly less than the amount the reactants will ultimately produce;
• and,
• flowing the reactant-containing slurry into the zone to be cemented and maintaining it substantially quiescent, so that, while the cement is setting and the volume of the aqueous liquid phase of the slurry is being reduced, the rate of the gas production is increased and the solidifying portions of the setting cement become both fluid impermeable and permeated with gas-filled, microscopically sized, clefts or creases which provide a bulk volume substantially equalling the initial bulk volume of the slurry.