TY - JOUR

T1 - Pressure loading histories and clay fraction effects on the static and dynamic elastic properties of sand-clay synthetic sediments

AU - Li, Hui

AU - Han, De hua

AU - Gao, Jinghuai

AU - Yuan, Hemin

AU - Wang, Yang

PY - 2019

Y1 - 2019

N2 - Investigations of the elastic mechanical characteristics of loosely compacted mixed sand-clay samples are essential for the characterization of shallow seafloor sedimentary reservoirs. Here, we used a series of sand-clay mixtures (0–100% clay by weight) to investigate the effects of pressure load histories (2–50 MPa) and clay fraction on porosity, P-wave velocity, S-wave velocity, and static modulus. The results indicated that, under pressure load cycles, the sand-clay mixture samples exhibited high permanent compaction, and porosity decreased rapidly with increasing clay content. However, porosity changed differently in response to pressure load as compared to pressure unload. Correspondingly, P-wave velocities differed significantly between pressure load and unload. The rock physical models implied that the sample frame evolved with the varying clay fraction. As the clay fraction increased, the sample frame gradually transitioned from primarily sand grains with dispersed pore-filling clay to primarily clay, ultimately transforming into a clay frame with dispersed sand grains. The measured data generally conformed to the theoretical model and falling within the Voigt and Reuss bounds. Moreover, for all sand-clay mixture samples, although the static bulk modulus was consistently lower than the dynamic bulk modulus, the ratio of the dynamic modulus to the static modulus was highly dependent on pressure loads and clay fraction.

AB - Investigations of the elastic mechanical characteristics of loosely compacted mixed sand-clay samples are essential for the characterization of shallow seafloor sedimentary reservoirs. Here, we used a series of sand-clay mixtures (0–100% clay by weight) to investigate the effects of pressure load histories (2–50 MPa) and clay fraction on porosity, P-wave velocity, S-wave velocity, and static modulus. The results indicated that, under pressure load cycles, the sand-clay mixture samples exhibited high permanent compaction, and porosity decreased rapidly with increasing clay content. However, porosity changed differently in response to pressure load as compared to pressure unload. Correspondingly, P-wave velocities differed significantly between pressure load and unload. The rock physical models implied that the sample frame evolved with the varying clay fraction. As the clay fraction increased, the sample frame gradually transitioned from primarily sand grains with dispersed pore-filling clay to primarily clay, ultimately transforming into a clay frame with dispersed sand grains. The measured data generally conformed to the theoretical model and falling within the Voigt and Reuss bounds. Moreover, for all sand-clay mixture samples, although the static bulk modulus was consistently lower than the dynamic bulk modulus, the ratio of the dynamic modulus to the static modulus was highly dependent on pressure loads and clay fraction.

KW - Elastic

KW - Granular material

KW - Mechanic behavior

KW - Pressure-dependent compaction

U2 - 10.1016/j.powtec.2019.01.033

DO - 10.1016/j.powtec.2019.01.033

M3 - Journal article

AN - SCOPUS:85061056768

VL - 345

SP - 804

EP - 814

JO - Powder Technology

JF - Powder Technology

SN - 0032-5910

ER -