Influencing factors analysis of hard limestone reformation and strength weakening under acidic effect

Abstract

Roof disaster has always been an important factor restricting coal mine safety production. Acidic effect can reform the rock mass structure to weaken the macroscopic strength characteristics, which is an effective way to control the hard limestone roof. In this study, the effects of various factors on the reaction characteristics and mechanical properties of limestone were analyzed. The results show that the acid with stronger hydrogen production capacity after ionization (pK_a<0) has more prominent damage to the mineral grains of limestone. When pK_a increases from −8.00 to 15.70, uniaxial compressive strength and elastic modulus of limestone increase by 117.22% and 75.98%. The influence of acid concentration is manifested in the dissolution behavior of mineral crystals, the crystal defects caused by large-scale acid action will lead to the deterioration of limestone strength, and the strength after 15% concentration reformation can be reduced by 59.42%. The effect of acidification time on limestone has stages and is the most obvious in the initial metathesis reaction stage (within 60 min). The key to the strength damage of acidified limestone is the participation of hydrogen ions in the reaction system. Based on the analytic hierarchy process method, the influence weights of acid type, acid concentration and acidification time on strength are 24.30%, 59.54% and 16.16%, respectively. The research results provide theoretical support for the acidification control of hard limestone roofs in coal mines.

Keywords

hard roof / acidic effect / structural reformation / strength weakening / influencing factors

References

[1] HeJ, DouL-m, MuZ-l, et al. . Numerical simulation study on hard-thick roof inducing rock burst in coal mine [J]. Journal of Central South University, 2016, 23(9): 2314-2320

[2] XieC-y, NguyenH, BuiX, et al. . Predicting roof displacement of roadways in underground coal mines using adaptive neuro-fuzzy inference system optimized by various physics-based optimization algorithms [J]. Journal of Rock Mechanics and Geotechnical Engineering, 2021, 13(6): 1452-1465

[3] RayS K, KhanA M, MohalikN K, et al. . Review of preventive and constructive measures for coal mine explosions: An Indian perspective [J]. International Journal of Mining Science and Technology, 2022, 32(3): 471-485

[4] HuangB-x, LiuJ-w, ZhangQuan. The reasonable breaking location of overhanging hard roof for directional hydraulic fracturing to control strong strata behaviors of gob-side entry [J]. International Journal of Rock Mechanics and Mining Sciences, 2018, 103: 1-11

[5] ZhangF-t, WangX-y, BaiJ-b, et al. . Fixed-length roof cutting with vertical hydraulic fracture based on the stress shadow effect: A case study [J]. International Journal of Mining Science and Technology, 2022, 32(2): 295-308

[6] ZhangX-y, HuJ-z, XueH-j, et al. . Innovative approach based on roof cutting by energy-gathering blasting for protecting roadways in coal mines [J]. Tunnelling and Underground Space Technology, 2020, 99: 103387

[7] ZhangX Y, PakR Y, GaoY B, et al. . Field experiment on directional roof presplitting for pressure relief of retained roadways [J]. International Journal of Rock Mechanics and Mining Sciences, 2020, 134104436

[8] MustafaA, AlyM, AljawadM S, et al. . A green and efficient acid system for carbonate reservoir stimulation [J]. Journal of Petroleum Science and Engineering, 2021, 205108974

[9] LuoZ-f, ZhangN-l, ZhaoL-q, et al. . An extended finite element method for the prediction of acid-etched fracture propagation behavior in fractured-vuggy carbonate reservoirs [J]. Journal of Petroleum Science and Engineering, 2020, 191107170

[10] AliM, ZiauddinM. Carbonate acidizing: A mechanistic model for wormhole growth in linear and radial flow [J]. Journal of Petroleum Science and Engineering, 2020, 186106776

[11] JafarpourH, AghaeiH, LitvinV, et al. . Experimental optimization of a recently developed matrix acid stimulation technology in heterogeneous carbonate reservoirs [J]. Journal of Petroleum Science and Engineering, 2021, 196108100

[12] MehrjooH, Norouzi-ApourvariS, JalalifarH, et al. . Experimental study and modeling of final fracture conductivity during acid fracturing [J]. Journal of Petroleum Science and Engineering, 2022, 208109192

[13] LiY-m, DengQ, ZhaoJ-z, et al. . Simulation and analysis of matrix stimulation by diverting acid system considering temperature field [J]. Journal of Petroleum Science and Engineering, 2018, 170932-944

[14] CaoC, ZhouF-j, ChengL-s, et al. . A comprehensive method for acid diversion performance evaluation in strongly heterogeneous carbonate reservoirs stimulation using CT [J]. Journal of Petroleum Science and Engineering, 2021, 203: 108614

[15] TianH-y, QuanH-p, HuangZ-y, et al. . Effects of two kinds of viscoelastic surfactants on thickening and rheological properties of a self-thickening acid [J]. Journal of Petroleum Science and Engineering, 2021, 197107962

[16] ZhaoM-w, LiY, XuZ-l, et al. . Dynamic cross-linking mechanism of acid gel fracturing fluid [J]. Colloids and Surfaces A-Physicochemical and Engineering Aspects, 2020, 607125471

[17] HouM-x, HuangB-x, ZhaoX-l, et al. . Evaluation model of hard limestone reformation and strength weakening based on acidic effect [J]. Minerals, 2023, 13(8): 1101

[18] SarmahA, IbrahimA F, Nasr-El-DinH, et al. . A new cationic polymer system that improves acid diversion in heterogeneous carbonate reservoirs [J]. SPE Journal, 2020, 2552281-2295

[19] ShiW Y, YaoY D, ChengS Q, et al. . Pressure transient analysis of acid fracturing stimulated well in multilayered fractured carbonate reservoirs: A field case in Western Sichuan Basin, China [J]. Journal of Petroleum Science and Engineering, 2020, 184106462

[20] AliM T, EzzatA A, Nasr-El-DinH. A model to simulate matrix-acid stimulation for wells in dolomite reservoirs with vugs and natural fractures [J]. SPE Journal, 2020, 25(2): 609-631

[21] LiuX-s, FanD-y, TanY-l, et al. . New detecting method on the connecting fractured zone above the coal face and a case study [J]. Rock Mechanics and Rock Engineering, 2021, 54(8): 4379-4391

[22] BianW-h, YangJ, HeM-c, et al. . Research and application of mechanical models for the whole process of 110 mining method roof structural movement [J]. Journal of Central South University, 2022, 293106-3124

[23] XuJ-m, ZhuW-b, XuJ-l, et al. . High-intensity longwall mining-induced ground subsidence in Shendong coalfield, China [J]. International Journal of Rock Mechanics and Mining Sciences, 2021, 141: 104730

[24] HanXuStudy on mechanical characteristics and conductivity of acid etch soften layer in limestone [D], 2018, Chengdu, China, Chengdu University of Technology(in Chinese)

[25] LiuX-pingExperimental study on the mechanical properties of limestone under acidic conditions [D], 2022, Mianyang, Southwest University of Science and Technology(in Chinese)

[26] DingW-x, FengX-ting. Testing study on mechanical effect for limestone under chemical erosion [J]. Chinese Journal of Rock Mechanics and Engineering, 2004, 23(21): 3571-3576(in Chinese)

[27] GuoJ, MiX-c, FengG-r, et al. . Study on mechanical properties and weakening mechanism of acid corrosion lamprophyre [J]. Materials, 2022, 15(19): 6634

[28] YuY, WangJ, FengG-l, et al. . Damage evolution and acoustic emission characteristics of hydrochemically corroded limestone [J]. Bulletin of Engineering Geology and the Environment, 2023, 824112

[29] MoY-c, ZuoS-y, WangLu. Mechanical characteristics of thick-bedded limestone with different bedding angles subjected to acid corrosion [J]. Bulletin of Engineering Geology and the Environment, 2022, 814166

[30] MustafaA, AlzakiT, AljawadM S, et al. . Impact of acid wormhole on the mechanical properties of chalk, limestone, and dolomite: Experimental and modeling studies [J]. Energy Reports, 2022, 8605-616

[31] HuangB-x, HouM-x, ZhaoX-l, et al. . Experimental investigation on the reformation and strength weakening of hard limestone by acidizing [J]. International Journal of Mining Science and Technology, 2022, 32(5): 965-979

[32] AlarjiH, AlzahidY, Regenauer-LiebK. Acid stimulation in carbonates: Microfluidics allows accurate measurement of acidic fluid reaction rates in carbonate rocks by quantifying the produced CO₂ gas [J]. Journal of Natural Gas Science and Engineering, 2022, 99104444

[33] RabieA I, GomaaA M, Nasr-El-DinH A. HCl/formic in-situ-gelled acids as diverting agents for carbonate acidizing [J]. SPE Production & Operations, 2012, 27(2): 170-184

[34] ChangF F, Nasr-El-DinH A, LindvigT, et al. Matrix acidizing of carbonate reservoirs using organic acids and mixture of HCl and organic acids [C], 2008

[35] AlhamadL, AlrashedA, Al-MunifE, et al. A review of organic acids roles in acidizing operations for carbonate and sandstone formations, 2020

[36] LuoJ, ZhuY-q, GuoQ-h, et al. . Chemical stimulation on the hydraulic properties of artificially fractured granite for enhanced geothermal system [J]. Energy, 2018, 142754-764

[37] GussenovI. Literary review: Permeability alterations in sandstone after acidizing [J]. Energy Reports, 2023, 9: 6328-6348

[38] CengelY A, BolesM A, KanogluM, et al. Thermodynamics: an engineering approach [M], 2011, New York, McGraw-Hill Education Press

[39] YooH, KimY, LeeW, et al. . An experimental study on acid-rock reaction kinetics using dolomite in carbonate acidizing [J]. Journal of Petroleum Science and Engineering, 2018, 168: 478-494

[40] ProtodyakonovM MMechanical properties and drillability of rocks [C], 1962, Minnesota, University of Minnesota Minneapolis

[41] MustafaA, AlzakiT, AljawadM S, et al. . Impact of acid wormhole on the mechanical properties of chalk, limestone, and dolomite: Experimental and modeling studies [J]. Energy Reports, 2022, 8: 605-616

[42] ZhangK-p, HouB, ChenM, et al. . Fatigue acid fracturing: a method to stimulate highly deviated and horizontal wells in limestone formation [J]. Journal of Petroleum Science and Engineering, 2022, 208: 109409

[43] SheM, ShouJ-f, ShenA-j, et al. . Experimental simulation of dissolution law and porosity evolution of carbonate rock [J]. Petroleum Exploration and Development, 2016, 43(4): 616-625

[44] LaiJ, GuoJ-c, MaY-x, et al. . Effect of acid-rock reaction on the microstructure and mechanical property of tight limestone [J]. Rock Mechanics and Rock Engineering, 2022, 5535-49

[45] ZhangH, ZhongY, ZhangJ, et al. . Experimental research on deterioration of mechanical properties of carbonate rocks under acidified conditions [J]. Journal of Petroleum Science and Engineering, 2020, 185106612

[46] ZhouB-c, JinY, XiongW, et al. . Investigation on surface strength of acid fracture from scratch test [J]. Journal of Petroleum Science and Engineering, 2021, 206109017