Statistical characterization of gas-patch distributions in partially saturated rocks
MetadataShow full item record
Published by the Society of Exploration Geophysicists
© 2009 Society of Exploration Geophysicists
The link to the journal’s home page is at : http://segdl.org/geophysics/
Reservoir rocks are often saturated by two or more fluid phases forming complex patterns on all length scales. The objective of this work is to quantify the geometry of fluid phase distribution in partially saturated porous rocks using statistical methods and to model the associated acoustic signatures. Based on X-ray tomographic images at submillimeter resolution obtained during a gas-injection experiment, the spatial distribution of the gas phase in initially water-saturated limestone samples are constructed. Maps of the continuous variation of the percentage of gas saturation are computed and associated binary maps obtained through a global thresholding technique. The autocorrelation function is derived via the two-point probability function computed from the binary gas-distribution maps using Monte Carlo simulations.The autocorrelation function can be approximated well by a single Debye correlation function or a superposition of two such functions. The characteristic length scales and show sensitivity (and hence significance) with respect to the percentage of gas saturation. An almost linear decrease of the Debye correlation length occurs with increasing gas saturation. It is concluded that correlation function and correlation length provide useful statistical information to quantify fluid-saturation patterns and changes in these patterns at the mesoscale. These spatial statistical measures are linked to a model that predicts compressional wave attenuation and dispersion from local, wave-induced fluid flow in randomly heterogeneous poroelastic solids. In particular, for a limestone sample, with flow permeability of 5 darcies and an average gas saturation of ~5%, significant P-wave attenuation is predicted at ultrasonic frequencies.
Showing items related by title, author, creator and subject.
Toms, Julianna J. (2008)Partial saturation of porous rock by two fluids substantially affects compressional wave propagation. In particular, partial saturation causes significant attenuation and dispersion due to wave-induced fluid flow. Such ...
Comparative review of theoretical models for elastic wave attenuation and dispersion in partially saturated rocksToms, J.; Mller, T.; Ciz, Radim; Gurevich, Boris (2006)Saturation of porous rocks with a mixture of two fluids (known as partial saturation) has a substantial effect on the seismic waves propagating through these rocks. In particular, partial saturation causes significant ...
Muller, T.; Caspari, E.; Qi, Q.; Rubino, J.; Velis, D.; Lopes, S.; Lebedev, Maxim; Gurevich, Boris (2015)The presence of fluids in the pore space of rocks causes wave attenuation and dispersion by the mechanism broadly known as wave-induced fluid flow (WIFF). WIFF occurs as a seismic wave that creates pressure gradients ...