SPE Journal
Volume 16, Number 4, December 2011, pp. 778-783

Summary

We quantify the influence of the initial nonwetting-phase saturation and porosity on the residual nonwetting-phase saturation using data in the literature and our own experimental results on sandpacks and consolidated sandstones. These experiments were conducted at ambient or elevated pressure and temperature (ETP) conditions. The principal application of this work is for carbon capture and storage (CCS) where capillary trapping is a rapid and effective way to render the injected CO₂ immobile, guaranteeing safe storage.

We introduce the concept of capillary-trapping capacity (C_trap) which is the product of residual saturation and porosity that represents the fraction of the rock volume that can be occupied by a trapped nonwetting phase. We show that the measured trapping capacity reaches a maximum of approximately 11% for porosities of 22%, which suggests an optimal porosity for CO₂ storage.

Introduction

CCS is a method to reduce anthropogenic CO₂ emissions and thereby mitigate potentially damaging climate change (Haszeldine 2009; IPCC 2005). In the CCS context, capillary trapping has been identified as a major mechanism to store CO₂ in the subsurface reliably and rapidly (Juanes et al. 2006; Flett et al. 2004; Kumar et al. 2005; Qi et al. 2009; Hesse et al. 2008; Obi and Blunt 2006). This means that significant quantities of CO₂ can be stored by capillary forces and it is not necessary to rely solely upon stratigraphic trapping.

Capillary trapping has been measured in oil/water, gas/water, and three-phase gas/water/oil systems (Agarwal 1967; Aissaoui 1983; Al-Mansoori et al. 2010; Chierici et al. 1963; Crowell et al. 1966; Delclaud 1991; Firoozabadi et al. 1987; Flett et al. 2004; Geffen et al. 1952; Iglauer et al. 2010; Irle and Bryant 2005; Jerauld 1997; Kantzas et al. 2001; Kleppe et al. 1997; Kralik et al. 2000; Land 1968a, b; Land 1971; Ma and Youngren 1994; McKay 1974; Mulyadi et al. 2000; Naar and Henderson 1961; Pentland et al. 2010a, b; Pentland et al. 2011; Plug 2007; Suekane et al. 2008a, b). While literature data have been mainly determined for gas/brine systems, CO₂ is injected as a supercritical (sc) phase in CCS projects into reservoirs at depths of approximately 800 m or more. In the sc state, CO₂ has a density similar to that of a liquid and a viscosity similar to that of a gas.

© 2011. Society of Petroleum Engineers

View full textPDF ( 410 KB )

History

• Original manuscript received: 24 February 2009
• Meeting paper published: 9 June 2009
• Revised manuscript received: 4 December 2010
• Manuscript approved: 16 April 2011
• Published online: 7 November 2011
• Version of record: 23 December 2011