Experimental study of portland cement/rock interface in relation to wellbore stability for carbon capture and storage (CCS)

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Conference Proceeding

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Primary cementing is carried out during the drilling and completions of wells and the main objective is to provide zonal isolation. For effective cementing, the cement should completely displace the drilling mud (water-clay mixture). In practice, this is never achieved as some of the mud is not displaced and remains in the wellbore. This study investigates the effect of the residual mud on the hydraulic conductivity of the cement-formation interface. Flow-through experiments were conducted at 14.48 MPa (2100 psi) overburden pressure with cement-rock composite cores and brine at a flow rate of 1 ml/min. The cement-rock composite cores had 0% and 10% clay-rich fluid contamination respectively. The pressure drop across the composite cores was recorded throughout the flow-through experiments. Extensive micro-structural characterization of the cement-rock interface was carried out before and after the flow-through experiments. Higher pH values were recorded for the effluent brine from the mud contaminated core and the higher values indicate increased leaching of Ca . Micro-CT imaging revealed that the contaminated composite core possessed higher porosity at the interface zone. This shows that clay contamination of cement-rock interface degrades the interface zone and can provide a pathway for injected CO to escape from the intended storage zone. Copyright 2012 ARMA, American Rock Mechanics Association. 2+ 2

Publication Source (Journal or Book title)

46th US Rock Mechanics / Geomechanics Symposium 2012

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