Acoustic emission monitoring of hydraulic fracturing laboratory experiment with supercritical and liquid CO₂

Abstract

[1] Carbon dioxide (CO 2 ) is often used for enhanced oil recovery in depleted petroleum reservoirs, and its behavior in rock is also of interest in CO 2 capture and storage projects. CO 2 usually becomes supercritical (SC-CO 2 ) at depths greater than 1,000 m, while it is liquid (L-CO 2 ) at low temperatures. The viscosity of L-CO 2 is one order lower than that of normal liquid water, and that of SC-CO 2 is much lower still. To clarify fracture behavior induced with injection of the low viscosity fluids, we conducted hydraulic fracturing experiments using 17 cm cubic granite blocks. The AE sources with the SC-and L-CO 2 injections tend to distribute in a larger area than those with water injection, and furthermore, SC-CO 2 tended to generate cracks extending more three dimensionally rather than along a flat plane than L-CO 2 . It was also found that the breakdown pressures for SC-and L-CO2 injections are expected to be considerably lower than for water.

Effect of Water Infiltration, Injection Rate and Anisotropy on Hydraulic Fracturing Behavior of Granite

“…Hydraulic fracturing behavior of different granites has been reported by Haimson (1975Haimson ( , 1999, Haimson and Lee (1980), Solberg et al (1980), Haimson and Doe (1983), Haimson and Zhao (1991), Zhao et al (1996), Ishida et al (1997Ishida et al ( , 2000Ishida et al ( , 2004Ishida et al ( , 2012 and Chen et al (2015). However, in these studies granites were mainly treated as low-permeability rocks and the influence of infiltration of injection fluid has rarely been discussed.…”

Mechanisms for CO2 Sequestration in Geological Formations and Enhanced Gas Recovery

“…As time increases the fingers become less conspicuous. Figure [2][3][4][5][6][7][8][9][10][11][12] shows that the pressure decline for oleic phase is stronger than for the other cases. qualitative correspondence between simulations and experiments is that there is a region of high concentration gradient near the gas-liquid interface.…”

“…The mass transfer is initially diffusion controlled. However, after number of numerical studies [12,18] show that the onset time of convection is inversely proportional to the Rayleigh number, which can be expressed as, c is a constant value and it covers a range between 55 and 4500.…”

“…Therefore, understanding the CO2-oil interaction during these processes is of great interest for the petroleum industry. The initial stage of natural convection in a saturated porous layer with a denser fluid on top of a lighter fluid has been extensively studied by means of linear stability analysis, numerical simulations and the energy method ( [4][5][6][7][8][9][10][11][12][13][14][15][16][17] [18] showed that the interface will be unstable for Rayleigh numbers above 2 4 40 π ≈ in porous media. In the absence of a porous medium (for bulk solutions), k in Equation (2.…”

“…The IPCC report suggests the following present or future options [5]: 1) -improve energy efficiency by decreasing the fossil fuel consumption, 2) -switching from high carbon to low carbon fuels, 3) -increased use of fuels with low or near zero carbon footprint, 4) -Storing CO2 through the enhancement of natural, biological sinks, 5) -CO2 capture and storage (CCS). To choose a mitigation option the potential and capacity of the option, social acceptance, side effect and more importantly the associated costs [10] and innovation [11,12] are key parameters. In a transition period from a fossil fuel based society to a sustainable energy society it is predicted that CO2 capture and subsequent sequestration (CCS) in geological formations can be developed to play a role in reducing greenhouse gas emissions [13].…”