摘要
蚀变型金矿石水压裂缝起裂扩展规律对水力压裂开采金矿具有重要意义,开展不同注水流量、不同最小水平主应力、不同注水孔与节理面夹角的蚀变型金矿石真三轴水力压裂实验。结果表明:(1)当蚀变型金矿石水平主应力差为1~3 MPa时,起裂应力为22.2~40.0 MPa;注水流量从5 mL/min增大到15,30 mL/min,起裂应力从16.53 MPa分别增大17.4%,34.3%;最小水平主应力从4 MPa增大到5,6 MPa,起裂应力从22.20 MPa分别增大37.4%,80.2%;注水孔与节理面夹角从0°增大到45°,90°,起裂应力从22.20 MPa分别增大6.3%,24.9%;在相近的地应力条件下,蚀变型金矿石比煤岩、灰岩、砂岩、页岩等沉积岩起裂应力更大;(2)蚀变型金矿石水压裂缝按扩展路径可分为直线扩展和折线扩展2种模式;注水流量从5 mL/min增大到15,30 mL/min,裂缝扩展方向与最小水平主应力方向垂直程度增高,转向次数由2次均减少至0次;最小水平主应力从4 MPa增大到5,6 MPa,裂缝转向次数由0次增加至1和3次,转向角度增大;注水孔与节理面夹角从0°增大到45°,90°,裂缝扩展方向受节理面干扰程度增大并偏向节理面扩展;蚀变型金矿石水压裂缝多为主裂缝,次级裂缝发育少分布简单,沉积岩次级水压裂缝数量多且分布复杂;(3)蚀变型金矿石裂缝面按照形貌特征可分为平滑裂缝面和粗糙裂缝面;注水流量从5 mL/min增大到15,30 mL/min,裂缝面凸起变小,凸起面积占裂缝面面积由63%降低至45%,0;最小水平主应力从4 MPa增大到5,6 MPa,凸起面积占裂缝面面积由0增至40%,45%;注水孔与节理面夹角从0°增大到45°,90°,裂缝面均保留节理面形貌特征且平滑无凸起;蚀变型金矿石裂缝面粗糙,而沉积岩裂缝面较平滑。
The initiation and propagation law of hydraulic fractures in altered gold ore hold paramount importance for the hydraulic fracturing exploitation of gold mines.This study conducted true triaxial hydraulic fracturing experiments on altered gold ore under varying water injection rates,minimum horizontal principal stresses,and angles between water injection holes and joint surfaces.Results indicate that:(1)when the difference in horizontal principal stress for altered gold ore ranges from 1 to 3 MPa,initiation stress spans 22.2 to 40.0 MPa.With increasing water injection rates(from 5 mL/min to 15 and 30 mL/min),initiation stress rises by 17.4%and 34.3%,respectively.An elevation in the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa)results in initiation stress increases by 37.4%and 80.2%,respectively.The angle between water injection holes and joint surfaces(from 0°to 45 and 90°)induces initiation stress increases by 6.3%and 24.9%,respectively.Altered gold ore,under similar in-situ stress conditions,exhibits higher initiation stresses compared to sedimentary rocks.(2)Hydraulic fractures in altered gold ore can be categorized into two modes:linear and polygonal propagation.Increasing water injection rates(from 5 mL/min to 15 and 30 mL/min)results in heightening perpendicularity between the fracture propagation direction and the minimum horizontal principal stress direction,with a reduction in the number of turns from 2 times to 0.An increase in the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa)leads to an increase in the number of turns from 0 to 1 and 3 times,with larger turning angles.With the increasing angle between water injection holes and joint surfaces(from 0°to 45 and 90°),interference from joint surfaces is intensified,causing propagation deviations towards the joint surfaces.Hydraulic fractures in altered gold ore predominantly exhibit main fractures,with fewer and simpler secondary fractures,whereas sedimentary rocks display a higher number of complexly distributed secondary fractures.(3)The fracture surfaces in altered gold ore can be classified based on morphological characteristics into smooth and rough surfaces.Increasing water injection rates(from 5 mL/min to 15 and 30 mL/min)results in a decrease in protrusion size on the fracture surfaces,with the protrusion area decreasing from 63%to 45%and 0%.Increasing the minimum horizontal principal stress(from 4 MPa to 5 and 6 MPa)leads to an increase in the protrusion area from 0%to 40%and 45%.Increasing the angle between water injection holes and joint surfaces(from 0°to 45°and 90°)all maintains joint surface features on the fracture surfaces with smooth and non-protruding characteristics.The fracture surfaces of altered gold ore are rough,while those of sedimentary rocks are comparatively smoother.
作者
于骞
刘江伟
陈绍杰
李亚康
YU Qian;LIU Jiangwei;CHEN Shaojie;LI Yakang(College of Energy and Mining Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266590,China)
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2024年第S01期3321-3332,共12页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(52174159,52074169)
山东省自然科学基金面上项目(ZR2022ME112)
关键词
采矿工程
蚀变型金矿石
水力压裂
起裂应力
扩展规律
形貌特征
mining engineering
altered gold ore
hydraulic fracturing
fracture initiation stress
fracture propagation law
fracture morphology characteristics
