| Hydraulic fracturing was one of the main measures for increasing the permeabilityof coal reservoir, the complexity of hydraulic fracturing crack forms was increased bynatural fracture system of coal seam, in the past, the study were being done mainly inthe laboratory condition or field experience, all these made the limitation of theoryguiding practice, and it was relatively small of theory combining with practice.Based on the thought of theory to combing with practice, at first coal samples’stress-strain-permeability in different degree of fracture and different coal structure wastested by applying the RMT-150B in the laboratory, the relationship among them wasfound out, the feasibility of the directness about hydraulic fracturing of type Ⅰ or Ⅱ coaland the limitation of type Ⅲ or IV coal was verified. According to the different targetbed of CBM exploitation, thus the two kinds of fracturing technology include singlecoal seam hydraulic fracturing and multiple seam layer hydraulic fracturing wereidentified. Based on the principle of hydraulic fracturing and the own characteristics ofcoal, the influencing factors of crack form and fracturing effect for single coal seamwere systematic analyzed, based on interval transit time test and statistical fracture areaunder the ten magnification, the original state of coal seam could be divided into facturewell-developed coal seam, fracture better-developed coal seam and fracturepoor-developed coal seam. The morphology model of different degree about fracturedid or not break through rock was respectively built, based on applying rock fracturemechanics theory to judge whether the hydraulic fracturing could break through thesurrounding rock or not, and combing with crack law of rupture extension; thepermeability prediction model was established, based on the Carman-Kozeng equationand combined with the characteristics of hydraulic fracturing in CBM well. Theparameter of different degree about fracture coal seam was optimized by using iterativemethod. In the same way, fracture morphology model and permeability predictionmodel were established and the construction parameters were optimized, based onanalyzing the influencing factors of multiple seam layer hydraulic fracturing, the cavefriction formula combined with fracture pressure.Finally, the hydraulic fracturing optimization software collection input data, call data, prediction, parameter optimization were realized by virtue of c#programminglanguage and it connected with the Access database. It shows that the software hadcertain reliability, and it could make accurate judgment according to the differentsituations according to the optimization results and actual results of Pan Zhuang blockand Gu Jiao block comparison.The hydraulic fracturing parameter optimization at the different live conditionscould be provided theoretical guidance, and the cost could be conserved by theparameter optimization and software development about hydraulic fracturing for type Ⅰor Ⅱ and high rank coal. |
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