METHOD OF MONITORING CARBON DIOXIDE LEAKAGE IN CARBON CAPTURE AND STORAGE RESERVOIRS

摘要

The method of monitoring carbon dioxide leakage in carbon capture and storage reservoirs estimates porosity and water saturation in a porous medium, such as brine-saturated shale, as is common in carbon capture and storage reservoirs, based upon measured electrical conductivity and seismic P-wave velocity. The estimated porosity and water saturation may be used for monitoring carbon dioxide leakage from a carbon dioxide reservoir to the overlying cap rock of the region. Measured electrical conductivity and seismic P-wave velocity data are used by the present method to estimate the porosity and water saturation in the cap rock. If a decrease in water saturation in the cap rock is found, this indicates that carbon dioxide may be leaking up from the carbon dioxide reservoir. An alert signal is then generated to indicate that there may be a carbon dioxide leak.

主权项

1. A method of monitoring carbon dioxide leakage in carbon capture and storage reservoirs, comprising the steps of:
(a) setting an integer i equal to zero; (b) measuring an electrical conductivity σ and a seismic P-wave velocity Vp at a cap rock location above a carbon dioxide storage reservoir; (c) calculating a porosity φ associated with the cap rock asVp=φKaKmKw+(φc-φ)(Km+43Gm)[φcKmKw(1-Sw)+Ka((1-φc)Kw+φcKmSw)]φc[φcKmKw(1-Sw)+Ka((1-φc)Kw+φcKmSw)][(1-Sw)φρa+(1-φ)ρm+φSwρw]where a water saturation Sw of the cap rock is given by:Sw=σ-(1-φ)σm-φσaφ(σw-σa),wherein σm is an electrical conductivity of a solid matrix of the cap rock, σw is an electrical conductivity of water in the cap rock, and σa is an electrical conductivity of air in the cap rock, Ka is a bulk modulus of the air in the cap rock, Km is a bulk modulus of the solid matrix of the cap rock, Kw is a bulk modulus of the water in the cap rock, φc is a critical porosity of the cap rock, Gm is a shear modulus of the solid matrix of the cap rock, ρa is a density of the air in the cap rock, ρm is a density of the solid matrix of the cap rock, and ρw is a density of the water in the cap rock;
(d) calculating an i-th value of the water saturation Swi of the cap rock as:Swi=σ-(1-φ)σm-φσaφ(σw-σa); (e) recording the i-th value of the water saturation Swi of the cap rock in non-transitory, computer-readable memory; and (f) if consecutive i-th values of the water saturation of the cap rock decrease, then generating an alert signal to indicate a carbon dioxide leak in the cap rock, and if the consecutive i-th values of the water saturation of the cap rock do not decrease, then setting i=i+1 and returning to step (b).