Compositions and Methods for Well Treatment

Abstract

A self-healing cement for use in wells in which carbon dioxide is injected, stored or extracted, comprises a carbonaceous material. In the event of cement-matrix failure, or bonding failure between the cement / casing interface or the cement / borehole-wall interface, the material swells when contacted by carbon dioxide. The swelling seals voids in the cement matrix, or along the bonding interfaces, thereby restoring zonal isolation.

Description

BACKGROUND OF THE INVENTION[0001]The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.[0002]This disclosure relates to compositions and methods for treating subterranean formations, in particular, compositions and methods for cementing and completing wells which penetrate subterranean formations, into which carbon dioxide is injected, stored or extracted.[0003]During the construction of subterranean wells, it is common, during and after drilling, to place a tubular body in the wellbore. The tubular body may comprise drillpipe, casing, liner, coiled tubing or combinations thereof. Usually, a plurality of tubular bodies are placed sequentially and concentrically, with each successive tubular body having a smaller diameter than the previous tubular body, set at selected depths as drilling progresses. The purpose of the tubular body is to support the wellbore and to act as a conduit through which desirabl...

AI Technical Summary

Benefits of technology

This patent relates to improving cement systems used in subterranean wells by making them self-healing in a carbon-dioxide environment. The use of a carbonaceous material in a cement slurry allows for the formation of a cement sheath that can repair itself when exposed to carbon dioxide. This helps to maintain zonal isolation in the well and ensures the proper cementing of subterranean wells.

Problems solved by technology

However, over time the cement sheath can deteriorate and become permeable.

Alternatively, the bonding between the cement sheath and the tubular body or borehole may become compromised.

The principal causes of deterioration and debonding include physical stresses associated with tectonic movements, temperature changes and chemical deterioration of the cement.

None of these concepts are immediately applicable to well-cementing operations because of the need for the cement slurry to be pumpable during placement, and because of the temperature and pressure conditions associated with subterranean wells.

However, the well-cementing industry also has to contend with wells into which carbon dioxide is injected, in which carbon dioxide is stored or from which carbon dioxide is recovered.

One of the challenges is to trap the carbon dioxide and prevent leakage back to the surface; maintaining a competent and impermeable cement sheath is a critical requirement.