Self-Adaptive Cement Systems

Abstract

A self-healing cement system includes cement, water and at least one additive that swells in contact with water from reservoir or from formation in the case of a structural failure in the set cement to provide a physical barrier in the zone of failure. Examples of such material include particles of super-absorbent polymer. These additives have the effect of making the cement self-healing in the event of physical failure or damage such as micro-annuli. The self healing property is produced by the contact of the water itself, the potential repair mechanism is thus activated if and when needed in case of start of loss of zonal isolation. Several super-absorbent polymers have been identified such as polyacrylamide, modified crosslinked poly(meth)acrylate and non-solute acrylic polymers.

Description

TECHNICAL FIELD OF THE INVENTION [0001] The present invention relates to adaptive cement systems. In particular, the invention relates to cement systems which are “self-healing”, i.e. system which can adapt to compensate for changes or faults in the physical structure of the cement, or which adapt their structure after the setting phase of the cement in the cementing of oil, gas, water or geothermal wells, or the like. BACKGROUND OF THE INVENTION [0002] During the construction of underground wells, it is common, during and after drilling, to place a liner or casing, secured by cement pumped into the annulus around the outside of the liner. The cement serves to support the liner and to provide isolation of the various fluid-producing zones through which the well passes. This later function is important since it prevents fluids from different layers contaminating each other. For example, the cement prevents formation fluids from entering the water table and polluting drinking water, o...

AI Technical Summary

Benefits of technology

[0006] More precisely, the present invention aims at providing well cementing systems that include at least one additive that reacts and / or swells when the set cement is in contact with an aqueous fluid, such as formation waters. This behavior has the effect of making the cement self-healing in the event of physical failure or damage.

[0011] It has been found that the addition of salts such as sodium chloride or calcium chloride for instance favors the rheology of the systems thereby enabling increasing the concentration of super-absorbent polymers. Cement slurries of lower density have also a greater acceptability of higher concentrations of super-absorbent polymers, even without salt.

Problems solved by technology

However, for various reasons, over time this sheath can deteriorate and become permeable.

None of these are immediately applicable to well cementing operations because of the need for the cement to be pumpable during placement and because of the pressure and temperature range.