Study On The Seepage Parameters Determination Method And Application Of The Coal Seam Gas Based On The Pressure Build-up Curves

The coal seam gas(the gas)occurrence parameters was the basic of mastering the coal seam gas emission law,the productivity prediction,the hazard controlling and the clean utilization,so the coal seam gas pressure and the permeability coefficient seepage parameters exactly determination had become essential foundation work in the coal seam disaster prevention and the resource mining.At present,the determination methods of the coal seam gas pressure,the gas content and the other seepage parameters generally used the direct determination method.The direct determination method had a high accuracy in the gas pressure determination,but it required high at pressure place,the determination period was too long,it can't meet the demand of the extracting coal face,especially to the coal seam excavation working face with gas outburst dangerous,rapidly and accurately determination the gas pressure was the key to improve the excavation speed and ensure the safety,the above determination method was difficult to meet the requirement of the rapid excavation at modern coal mine.The application technology of the pressure build-up curves was based on the oilfield groundwater dynamics,the method had become a common and essential method in the oil and gas field development.The oil well analysis and deduction method applied to the gas well was consistent in the guidance production safety.This thesis mainly studied the coal seam gas build-up curves technology and methods suitable for the coal seam gas seepage parameters determination in underground coal mine,and developed the complete determination equipment,to guide the gas drainage,the coal and gas outburst prevention and high efficient coal bed gas extraction.The research results were as follows:Taking the maturity theory and basic formulas of the pressure build-up curves in oil and gas well for reference,combing with the coal seam occurrence characteristics,the feasibility and applicability of the the pressure build-up curves which was used in the coal seam gas seepage parameters determination were analyzed.Taking the pressure build-up curves as the basis,combing with the mathematical analysis method and the practice method,the gas pressure,the gas permeability parameters determination methods of the gas well and the drilling were studied,the coal seam gas pressure build-up curves testing method was proposed which can calculate the coal seam gas pressure,the permeability parameters and the other seepage parameters.Considering the anisotropic material mechanics,the anisotropy seepage flow stress coupling model of the coal seam gas flow had built based on the elastic mechanics and the seepage mechanics,combining with the coal seam gas pressure test method,the test results and the occurrence characteristics;considering the coal cleat structure characteristics and the gas adsorption desorption law,the coal seam gas pressure build-up curves numerical model and method were constructed,applying in the gas pressure build-up curves numerical simulation,forming the method of the gas pressure build-up curves calculate the gas pressure slope section.The coal seam gas pressure build-up curves numerical simulation were carried out in different working conditions by the orthogonal tests,the results showed that the relationship between the gas pressure build-up curves slope section and the production time,the coal thickness,the overlying load(depth),the gas content was linear variation;the relationship between the slope section and the production time,the overlying load(depth),the gas content was positive related linear change,and negative related linear change with the coal seam thickness;the relationship between the slope section and the coal seam permeability coefficient was power function change,the index of the power function was negative number.In addition,the influences of the production time,the coal seam thickness,the overlying load(depth),the gas content on the gas pressure build-up curves slope was smaller,the influence of the gas content on the gas pressure build-up curves slope section was the most significant.Based on the pressure build-up curves theoretical research results,the coal seam gas seepage parameters measurement equipment was developed combined with the field test technique;the equipment was constituted by the pressure sensor,the flow sensor,the temperature sensor and the power supply,which can display the results on the touch screen with real-time curve,and use the embedded software calculate the gas pressure value and other seepage parameters.In addition,analyzing the existing bore hole sealing equipment application situation,the sealing pore equipment designing schemes and online leak sealing technique were determined,the sealing pore equipment was designed,and the laboratory and field experiments were carried out.Using the method of the pressure build-up curves to determine the coal seam gas seepage seepage parameters of 19 pressure drillings at 12 coal mines,the results show that the proposed testing method of the coal seam gas seepage parameters determination can be suitable for the coal mine gas occurrence parameters test.the seepage parameters results determined by the coal seam gas pressure build-up curves were the same with the common method determined results,but the pressure build-up curves method can determine the coal seam gas pressure in short time(the determine period of the pressure build-up curves was 1/3?1/2 than the common method),which can reduce the coal seam gas determining period,guarantee the working of excavation carry out smoothly and achieve the high safety and high effective production of coal mine.