Experimental Method to Simulate Coal Fines Migration and Coal Fines Aggregation Prevention in the Hydraulic Fracture

The Origins of Low‐Fracture Conductivity in Soft Shale Formations: An Experimental Study

“…Thee xperimental apparatus used in this work was mainly based on am odified API standard fracture-conductivity instrument that consisted of an automated hydraulic intensifier system, af luid injection system,ac onductivityc ell, and ad ata acquisition system ( Figure 1). [28] Large shale samples ( Figure 2a)w ere cut into dimensions of 17.7 cm long, 3.8 cm wide,a nd approximately 1.0 cm thick to fit the shape of the conductivityc ell. Thes tandard cores for fracture-conductivity tests were flat plates with smooth surfaces,a ss howni n Figure 2b.T he testr esults of these cores were reasonable if we treated the hydraulic fracture as ap lanar pattern with two symmetric wings in conventional formations.H owever, complexf racture networks are always generated in shale formationst hrough interactions between artificial fractures and preexistingd iscontinuity planes,s uch as bedding planes and natural fractures.T wo zones are commonly created, namely, proppant-invaded and no-proppant dilatant zones.T he proppant-invaded zone is the stimulated area that is filled properly with proppants.T he dilatantz one is the permanent open area of ap reexistingd iscontinuity plane createdb yt he wedginga ction of the proppants as they fill fracture tips as well as rock mass rotation or shear slippage,w hich leads to as elf-supportinge ffect.…”

Permeability variation associated with fines production from anthracite coal during water injection

“…(A-4) where e = 1.6 × 10 −19 C, c i = 6.02 × 10 19 /m 3 (1 × 10 −4 mol/m 3 ), z i = 1 for counterions and −1 for co-ions (i = 1, 2 respectively), k B = 1.38 × 10 −23 JK −1 and T = 298.15 K. surface potentials φ 01 and φ 02 can be represented in terms of zeta potential (Khilar and Fogler, 1999). Zou et al (2014) give the zeta potential of coal fines in distilled water as − 20 mV. Zeta potential of kaolinite fines has been reported to be − 33 to − 39 mV in sodium chloride brine with concentration variation from 10 − 2 to 10 − 4 mol/L in about pH neutral condition (Khilar and Fogler, 1984).…”

Swelling of clay minerals and its effect on coal permeability and gas production: A case study of southern Qinshui Basin, China

“…The swelling ability of illite is relatively weak . Even though kaolinite has no swelling ability, it can easily disperse and migrate in the low salinity water and then block the pore throats, which also damage the formation permeability . Moreover, as the fluid velocity sensitivity is also caused by the particle migration and blocking in pore throats, this study only takes the expansion of clay minerals into consideration in order to distinguish the velocity sensitivity and water sensitivity.…”