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Experimental study of sealing performance: Effects of particle size and particle‐packing state on threshold pressure of sintered compacts
Author(s) -
Sorai Masao,
Fujii Takashi,
Kano Yuki,
Uehara Shinichi,
Honda Katsuya
Publication year - 2014
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1002/2014jb011177
Subject(s) - materials science , supercritical fluid , sintering , mineralogy , porosity , particle size , particle (ecology) , composite material , analytical chemistry (journal) , thermodynamics , chemistry , chromatography , geology , physics , oceanography
Threshold pressure P c th (kPa), a parameter controlling rock's sealing performance in cases of CO 2 geological sequestration, was studied in a supercritical CO 2 ‐water system under conditions of 1000 m depth (10 MPa and 40°C). With respect to correlation between P c th and another important parameter of permeability, k (mdarcy), the closest‐packing structure of spherical particles is defined theoretically as a line having slope of −0.5 on a double logarithmic plot. This study found this line by measuring P c th of a capillary plate with known throat diameter as P c th = 188.8 k – 0.5 . This function is directly applicable to different depth and salinity conditions, although it requires minor correction at some temperature conditions. As a first step in determining the range of variation of rocks' P c th and k from internal particle structures, we used sintered compacts of uniform spherical silica particles with diameters of 0.1–10 µm. Results show that measured values of sintered compacts were scattered around the closest‐packing line, with the difference of packing state depending on different sintered additives and sintering temperatures. The change of packing state, occurring independently of resultant changes of porosity, varied sensitively according to P c th . Therefore, P c th is inferred to depend strongly on the local structure within rocks. The Knudsen number estimated for supercritical CO 2 at 1000 m depth indicated that CO 2 transmuted into a noncontinuum at k < 0.1 µdarcy in the closest‐packing structure. Future studies should consider whether the concept of P c th is applicable in this situation.