{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,1]],"date-time":"2026-02-01T05:25:59Z","timestamp":1769923559026,"version":"3.49.0"},"reference-count":31,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2017,9,13]],"date-time":"2017-09-13T00:00:00Z","timestamp":1505260800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Energies"],"abstract":"<jats:p>Hydraulic fracturing is used widely to stimulate coalbed methane production in coal mines. However, some factors associated with conventional hydraulic fracturing, such as the simple morphology of the fractures it generates and inhomogeneous stress relief, limit its scope of application in coal mines. These problems mean that gas extraction efficiency is low. Conventional fracturing may leave hidden pockets of gas, which will be safety hazards for subsequent coal mining operations. Based on a new drilling technique applicable to drilling boreholes in coal seams, this paper proposes a tree-type fracturing technique for stimulating reservoir volumes. Tree-type fracturing simulation experiments using a large-scale triaxial testing apparatus were conducted in the laboratory. In contrast to the single hole drilled for conventional hydraulic fracturing, the tree-type sub-boreholes induce radial and tangential fractures that form complex fracture networks. These fracture networks can eliminate the \u201cblank area\u201d that may host dangerous gas pockets. Gas seepage in tree-type fractures was analyzed, and gas seepage tests after tree-type fracturing showed that permeability was greatly enhanced. The equipment developed for tree-type fracturing was tested in the Fengchun underground coal mine in China. After implementing tree-type fracturing, the gas extraction rate was around 2.3 times greater than that for traditional fracturing, and the extraction rate remained high for a long time during a 30-day test. This shortened the gas drainage time and improved gas extraction efficiency.<\/jats:p>","DOI":"10.3390\/en10091388","type":"journal-article","created":{"date-parts":[[2017,9,13]],"date-time":"2017-09-13T10:17:32Z","timestamp":1505297852000},"page":"1388","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":24,"title":["A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs"],"prefix":"10.3390","volume":"10","author":[{"given":"Qian","family":"Li","sequence":"first","affiliation":[{"name":"State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China"},{"name":"National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yiyu","family":"Lu","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China"},{"name":"National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zhaolong","family":"Ge","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China"},{"name":"National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7992-9722","authenticated-orcid":false,"given":"Zhe","family":"Zhou","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China"},{"name":"National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jingwei","family":"Zheng","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China"},{"name":"National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Songqiang","family":"Xiao","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044, China"},{"name":"National & Local Joint Engineering Laboratory of Gas Drainage in Complex Coal Seam, Chongqing University, Chongqing 400044, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,9,13]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"100","DOI":"10.1016\/j.fuel.2015.07.082","article-title":"Best practices for the determination of low-pressure\/permeability coalbed methane reservoirs, Yuwu Coal Mine, Luan mining area, China","volume":"160","author":"Tian","year":"2015","journal-title":"Fuel"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"6881","DOI":"10.3390\/en8076881","article-title":"Coal and coalbed methane co-extraction technology based on the ground movement in the Yangquan coalfield, China","volume":"8","author":"Hu","year":"2015","journal-title":"Energies"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"063001","DOI":"10.1088\/1742-2132\/11\/6\/063001","article-title":"Deep coal seams as a greener energy source: A review","volume":"11","author":"Ranathunga","year":"2014","journal-title":"J. Geophys. Eng."},{"key":"ref_4","first-page":"2496","article-title":"Increasing permeability mechanism using directional cumulative blasting in coal seams with high concentration of gas and low permeability","volume":"34","author":"Mu","year":"2013","journal-title":"Rock Soil Mech."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"40","DOI":"10.1016\/j.coal.2009.04.005","article-title":"Improvement of methane drainage in high gassy coal seam using waterjet technique","volume":"79","author":"Lu","year":"2009","journal-title":"Int. J. Coal Geol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"538","DOI":"10.1016\/j.jngse.2016.04.043","article-title":"Coupled analysis about multi-factors to the effective influence radius of hydraulic flushing: Application of response surface methodology","volume":"32","author":"Kong","year":"2016","journal-title":"J. Nat. Gas Sci. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Zhang, Z.B., and Li, X. (2016). Numerical study on the formation of shear fracture network. Energies, 9.","DOI":"10.3390\/en9040299"},{"key":"ref_8","first-page":"1","article-title":"Horizontal respect distance for hydraulic fracturing in the vicinity of existing faults in deep geological reservoirs: A review and modelling study","volume":"3","author":"Westwood","year":"2017","journal-title":"Geomech. Geophys. Geo-Energy Geo-Resour."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"976","DOI":"10.1016\/j.ijrmms.2011.06.004","article-title":"Hydraulic fracturing after water pressure control blasting for increased fracturing","volume":"48","author":"Huang","year":"2011","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"831","DOI":"10.1016\/j.ijmst.2012.12.013","article-title":"Guiding-controlling technology of coal seam hydraulic fracturing fractures extension","volume":"22","author":"Zhai","year":"2012","journal-title":"Int. J. Min. Sci. Technol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/j.ijmst.2011.08.007","article-title":"Directional hydraulic fracturing to control hard-roof rockburst in coal mines","volume":"22","author":"Fan","year":"2012","journal-title":"Int. J. Min. Sci. Technol."},{"key":"ref_12","first-page":"1326","article-title":"Technology and application of directional hydraulic penetration permeability improvement by guided groove","volume":"37","author":"Wang","year":"2012","journal-title":"J. China Coal Soc."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"190","DOI":"10.1016\/j.jngse.2015.08.054","article-title":"A novel method of orienting hydraulic fractures in coal mines and its mechanism of intensified conduction","volume":"27","author":"Liu","year":"2015","journal-title":"J. Nat. Gas Sci. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"960","DOI":"10.1016\/j.jngse.2015.07.033","article-title":"Novel integrated techniques of drilling-slotting-separation-sealing for enhanced coal bed methane recovery in underground coal mines","volume":"26","author":"Zou","year":"2015","journal-title":"J. Nat. Gas Sci. Eng."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"571","DOI":"10.1016\/j.jngse.2015.01.008","article-title":"A novel ECBM extraction technology based on the integration of hydraulic slotting and hydraulic fracturing","volume":"22","author":"Yan","year":"2015","journal-title":"J. Nat. Gas Sci. Eng."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"5","DOI":"10.1016\/j.ijrmms.2016.03.024","article-title":"A typical evolution of seismicity patterns resulting from the coupled natural, human-induced and coseismic stresses in along wall coal mining environment","volume":"86","author":"Kozlowska","year":"2016","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"14260","DOI":"10.3390\/en81212426","article-title":"Research on and design of a self-propelled nozzle for the tree-type drilling technique in underground coal mines","volume":"8","author":"Lu","year":"2015","journal-title":"Energies"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1017\/S0305004100025585","article-title":"The distribution of stress in the neighbourhood of a flat elliptical crack in an elastic solid","volume":"46","author":"Green","year":"1950","journal-title":"Math. Proc. Camb. Philos. Soc."},{"key":"ref_19","doi-asserted-by":"crossref","unstructured":"Palmer, I.D. (1993, January 26\u201328). Induced Stresses Due to Propped Hydraulic Fracture in Coalbed Methane Wells. Proceedings of the Low Permeability Reservoirs Symposium, Denver, CO, USA.","DOI":"10.2523\/25861-MS"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"27","DOI":"10.1016\/0040-1951(79)90353-6","article-title":"On the mechanical interaction between a fluid-filled fracture and the earth\u2019s surface","volume":"53","author":"Pollard","year":"1979","journal-title":"Tectonophysics"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"12251","DOI":"10.1029\/93JB00779","article-title":"Joint pattern development: Effects of subcritical crack growth and mechanical crack interaction","volume":"98","author":"Olson","year":"1993","journal-title":"J. Geophys. Res."},{"key":"ref_22","first-page":"438","article-title":"The relationship between fracture complexity, reservoir properties, and fracture-treatment design","volume":"25","author":"Cipolla","year":"2010","journal-title":"Soc. Pet. Eng."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"17481","DOI":"10.1029\/96JB00882","article-title":"Progress toward a stochastic rock mechanics model of engineered geothermal systems","volume":"101","author":"Watanabe","year":"1996","journal-title":"J. Geophys. Res."},{"key":"ref_24","first-page":"183","article-title":"A shear dilation stimulation model for production enhancement from naturally fractured reservoirs","volume":"7","author":"Hossain","year":"2002","journal-title":"Soc. Pet. Eng."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Rubin, B. (2010). Accurate simulation of non-darcy flow in stimulated fractured shale reservoirs. Soc. Pet. Eng.","DOI":"10.2118\/132093-MS"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"375","DOI":"10.1016\/0022-1694(84)90090-8","article-title":"Determination of formation permeability by double-packer tests","volume":"72","author":"Braester","year":"1984","journal-title":"J. Hydrol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"326","DOI":"10.1016\/j.fuel.2013.09.035","article-title":"The mechanisms of gas generation during coal deformation: Preliminary observations","volume":"117","author":"Xu","year":"2014","journal-title":"Fuel"},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"2667","DOI":"10.1016\/j.fuel.2007.03.020","article-title":"The mechanical behaviour of coal with respect to CO2 sequestration in deep coal seams","volume":"86","author":"Viete","year":"2007","journal-title":"Fuel"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"391","DOI":"10.1016\/j.fuel.2016.10.116","article-title":"An experimental investigation of applicability of CO2 enhanced coal bed methane recovery to low rank coal","volume":"189","author":"Ranathunga","year":"2017","journal-title":"Fuel"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"13","DOI":"10.1007\/s40948-016-0042-2","article-title":"A macro-scale view of the influence of effective stress on carbon dioxide flow behaviour in coal: An experimental study","volume":"3","author":"Ranathunga","year":"2017","journal-title":"Geomech. Geophys. Geo-Energy Geo-Resour."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"766","DOI":"10.1111\/1365-2478.12435","article-title":"Changes in geophysical properties caused by fluid injection into porous rocks: Analytical models","volume":"65","author":"Pride","year":"2017","journal-title":"Geophys. Prospect."}],"container-title":["Energies"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1996-1073\/10\/9\/1388\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:44:48Z","timestamp":1760208288000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1996-1073\/10\/9\/1388"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,9,13]]},"references-count":31,"journal-issue":{"issue":"9","published-online":{"date-parts":[[2017,9]]}},"alternative-id":["en10091388"],"URL":"https:\/\/doi.org\/10.3390\/en10091388","relation":{},"ISSN":["1996-1073"],"issn-type":[{"value":"1996-1073","type":"electronic"}],"subject":[],"published":{"date-parts":[[2017,9,13]]}}}