Investigation on temperature pressure and permeability characteristics of coal affected by acetic acid
ZHENG Chunshan
LIU Tao
XUE Sheng
JIANG Bingyou
HAN Feilin
REN Bo
ZHAO Yang
Abstract：In order to reveal the permeability enhancement mechanism of coal treated by safe and environmental-friendly low-concentration acetic acid with considering multi-phase and multi-field ef-fects,a coupling theoretical model incorporating gas-water phases and stress-chemistry-temperature-diffusion-seepage fields was established to analyze the variation characteristics of cal-cite concentration,hydrogen ion concentration and temperature value of the coal affected by acetic acid.Through adopting the magnetic resonance and ultrasonic wave experimental tests,the im-provement principles of pore and seepage characteristics was investigated.Meanwhile,the chang-ing laws of effective air pressure and water pressure was revealed.The effects of acetic acid concen-tration,initial gas pressure,water saturation,Langmuir volume constant and ultimate adsorption expansion deformation on the permeability and gas extraction characteristics were further analyzed.The results show that:affected by acetic acid,the calcite concentration,H+concentration and tem-perature value of the coal both decrease.The calcite concentration and H+concentration drop to ap-proximately 550 and 0.07 mol/m3,respectively.The coal temperature decreases with the increasing gas drainage time due to the effects of dissolution of calcite and desorption of gas(about 0.942 4 times of the original).Acetic acid treatment contributes to pore and fracture development,resulting in 18 times of permeability increase after 120 d of gas drainage.The NMR spectra of coal samples all show decrease in micro-small and medium pore peaks and increase in large pore peaks.The ultra-sonic attenuation coefficients and ratios of coal samples W2-6％HAc,W3-12％HAc and W4-18％HAc rise.Among which,the increasing degree of W3-12％HAc is the highest,being about 1 583％and 1 388％.This is validated with the acetic acid treatment's permeability enhancement effect.At 120 d of gas extraction,the effective air pressure in treated coal decreases from 0.70 MPa to 0.23 MPa,while the effective water pressure reduces from 0.75 MPa to 0.06 MPa.With the in-creasing acetic acid concentration,ultimate adsorption expansion deformation and water saturation,the coal permeability increases significantly.The range of"low-temperature zone"around borehole decreases with bigger Langmuir volume constant and initial gas pressure,with the lowest tempera-ture value also drops.The results could provide references for obtaining enhancement mechanism of permeability and gas extraction efficiency in coal treated by acetic acid.
Keywords：pore fracturetemperature pressure propertiesseepage characteristicsmulti-parameter effect mechanism
Publication Date：2026-01-30
Online Publishing Date：2026-01-28(First online date of this platform, not the publication date of the document)
Pages：18( 118-135 )