ÇAĞRILI KONUŞMALAR / KEYNOTES Invited Speeches ... - TPJD

The Effect of CO 2 Saturated Brine on Artificially Fractured Well-Cement
Mustafa Hakan Özyurtkan 1 , Tevfik Yalçınkaya 2 , Mileva Radonjic 2
1 Istanbul Technical Unıversity, Faculty of Mines, Department of Petroleum and Natural Gas
Engineering, Ankara
2 Louisiana State University, Department of Craft&Hawkins Petroleum Engineering, Louisiana,
USA
Carbon capture and storage is one of the technologies that could help reduce CO 2 concentration
in the atmosphere. Depleted oil and gas fields are favorable targets for CO 2 storage because
existing wells can be readily used as injection wells. Wellbore cement is very important in
wellbore systems that serve as a barrier between different zones in the subsurface. The fractures
inside wellbore cement sheath, one of the possible pathways for CO 2 leakage to surface and/
or fresh water aquifers, impair the effective sealing of the wellbore cement. The existence of
fractures poses a risk for Carbon capture and storage. The purpose of this experimental study
is to examine the effect of CO 2 saturated acidic brine on the behavior of cement fracture and
porosity. Flow-through experiments were performed atmospheric and high pressure conditions,
using CO 2 saturated brine. Fracture widening was observed in CT images of the atmospheric
pressure experiment. The atmospheric pressure experiment resulted in the reduction of porosity.
The porosity reduction was caused by calcite deposition which was confirmed by mineralogical
analysis and ESEM images. The alteration of density along the fracture was observed by Helical
CT analysis. There were 2 mechanisms working simultaneously: leaching and precipitation
(carbonation). Leaching resulted in an increase in porosity whereas carbonation resulted in
a reduction of porosity. In a possible leakage scenario, acidic brine exposure may result in a
variation on fracture aperture and porosity.
Keywords : Cement Fractures, hydraulic conductivity, permeability, microstructures, well
cement durability
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