 |
| Titel |
Determining the mechanical strength of CO2-induced reaction zones in wellbore cement: is it worth it? |
| VerfasserIn |
Suzanne Hangx, Fons Marcelis, Arjan van der Linden, Emilia Liteanu |
| Konferenz |
EGU General Assembly 2015
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104752
|
| Publikation (Nr.) |
 EGU/EGU2015-4187.pdf |
|
|
|
|
|
| Zusammenfassung |
| CO2 injection, either for long-term CO2 storage (CCS) or Enhanced Oil Recovery (EOR),
strongly hinges on maintaining storage integrity. Injection and legacy wells penetrating the
caprock pose one of the most likely points of leakage. In order to be able to predict the
long-term integrity of such wellbores, it’s important to understand their chemical,
hydrological and mechanical behaviour, and how it may change due to CO2 exposure.
Generally, in response to CO2/brine/cement interactions, a number of different reaction zones
are observed, each with their own chemical, and hence mechanical, signature. To aid
mechanical modelling efforts, assessing the risk of cement failure caused by stress
and temperature changes, knowledge is required of the strength of each of these
zones.
We performed experiments on Class G Portland cement to investigate the
chemical-mechanical coupling due to CO2-exposure. Batch reaction experiments, in the
presence of CO2-rich brine, were performed under typical storage conditions (T = 65Ë
C, PCO2 = 8 MPa) for various periods of time (1, 2, 3, 4, 5 and 6 months). After
exposure, mechanical tests were performed on the observed reaction zones, using
the so-called core scratching technique, to evaluate the unconfined compressive
strength (UCS) as a function of exposure time. Chemical analyses (CT-imaging,
SEM microscopy, EDX chemical analysis) showed the formation of three reaction
zones, similarly to what has been observed in other studies. Measurements of the
mechanical strength of these different zones showed highly variable results. Such
variations have also been observed in other studies, using different measurement
techniques. The large variability in strength measurements is most likely an inherent
result of the heterogenic nature of cement, which affects the extent and location of
reaction throughout the sample. This begs the question: is it worth studying the
mechanical strength of reaction-induced zones in cement? Or will it suffice to take into
account large uncertainties when modelling the mechanical behaviour of cement? |
|
|
|
|
|
|