--> ABSTRACT: Effects of Pore-Level Rock Properties on Injectivity and Storage Capacity of CO2 in Depleted Oil and Gas Fields and Saline Reservoirs, by Kaldi, John; #90135 (2011)

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Effects of Pore-Level Rock Properties on Injectivity and Storage Capacity of CO2 in Depleted Oil and Gas Fields and Saline Reservoirs

Kaldi, John 1
(1)CO2CRC Australian School of Petroleum, University of Adelaide, Adelaide, SA, Australia.

Volumetric calculations of storage capacity are commonly generic, formula-based calculations incorporating area, thickness, density, porosity and some "efficiency" factor. However, site-specific rock properties, such as pore geometry (pore to pore throat relationship), and capillary pressure properties (drainage and imbibition cycles) can provide insights on understanding CO2 storage capacity in both depleted fields and saline formations. Utilizing these techniques it is possible to determine how much pore volume is taken up, and is therefore inaccessible for CO2 saturation, by irreducible water saturation (Swirr) in saline formation target reservoirs and residual oil or gas saturation (Sor, Sgr) in depleted oiland gas fields. In addition, it is possible to determine, on a field scale, how much residual CO2 saturation can be expected during the buoyancy (gravity) driven migration of injected CO2 plumes. Injectivity (volume of injection over time) is controlled by factors such as permeability, area of wellbore and the difference in formation and injection pressure. It is optimal to maintain injectivity below the frac gradient (pressure required to fracture the formation). Locally, water production wells can relieve pressure and are thus able to provide a greater pressure margin for increased storage. By optimising CO2 injection and water offtake well locations, it may be also possible to engineer the direction of plume migration (“plume steering”).

 

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.