Research On Ground Stress Test And Control Measures Of Coal Seam Gas Hydraulics In Baijiao Coal Mine

With the development of C hina’s social economy,coal demand gradually increased,so that C hina’s coal mining depth gradually deepened and coal seam gas permeability is gradually reduced,so C hinese coal mine gas disaster is also very serious.Although China has made great progress in mine gas drainage,but for the complex geological conditions of low permeability coal seam,drilling gas extraction efficiency is generally low.It is difficult to measure the gas.In this paper,the gas drainage problem of low permeability coal seam under complicated geological conditions is put forward.And the method of theoretical analysis and field experiment is used to study the mechanism and effect of hydraulic plugging in low permeability coal seam under complex geological conditions.Made the following results:(1)By analyzing the influence of ground stress on hydraulic fracturing and hydraulic cutting,the necessity of geostress measurement is pointed out.The stress in the vicinity of the floor of the 238 floor of Baijiao Coal Mine was measured by the method of casing stress relief and get the in-situ stress state near 238 floor.The main controlling factors of ground stress in Baijiao coal mine are analyzed.Maximum principal stress 21.4 MPa Direction 90.1 ° inclination-6.7 °,intermediate principal stress 15.6MPa direction 358.1 ° inclination-16.8 °,minimum principal stress 6.9MPa direction 201.1 ° inclination-71.8 °.(2)The advantages and disadvantages of hydraulic fracturing and hydraulic cutting and its applicability are analyzed.Based on this,the hydraulic fracturing of the complex geological and low permeability coal seam is proposed.The technology combines the hydraulic fracturing of the two hydraulic hydraulics measures.For the low permeability coal seam,the hydraulic fracturing is used to increase the permeability of the area.After the construction of the hydraulic fracturing is completed,the extraction effect of the extraction hole is checked to determine the area with poor extraction efficiency as the "blind spot" of hydraulic fracturing,In the process of excavation and exploitation,the gas exceeding limit is also used as the "blind spot",and the localized gas is rapidly reduced by the local reinforcement of the hydraulic cutting seam,so as to meet the corresponding requirements.(3)The formula of hydraulic fracturing initiation pressure is determined by analyzing the stress state around the borehole,and the starting pressure of hydraulic fracturing iscalculated based on the results of ground stress measurement,which can better guides the field experiment.The hydraulic fracturing experiment was carried out,the influence range and the effect of hydraulic fracturing were analyzed.From the influence range of hydraulic fracturing,it can be seen that the fractured fractures are unevenly distributed.Due to the geological structure in the area,the fluctuation of coal seam and the thickness change are large,and there is a blind spot in hydraulic fracturing.After hydraulic fracturing,stable gas production amount rise 3 fracturing,gas drainage concentration and flow were 238 floor routine road wear layer boreholes is greatly improved,and the gas concentration and flow attenuation,effective pumping after fracturing gas drainage drilling production time.The average extraction concentration of pumping boreholes in fractured area is 58.6%,and the average single hole extraction purity is about 34.94 L/min.Feed concentration and flow pumping compared Baijiao mine daily single hole gas,hydraulic fracturing shows regional gas permeability increasing technology suitable for regional enhancement,has a good effect.(4)This paper analyzes the rock breaking principle of hydraulic slotting and pressure relief principle,and application of hydraulic slotting.After the production parameters of hydraulic slotting,compared with before cutting have improved slotted hole pumping gas at the same time,cut penetration zone drainage borehole gas concentration increased an average of 4.9 times,an average increase of 3.3 times of pure gas flow;But the slotted hole gas drainage short period of validity,production flow and concentration of gas cutting hole is smaller,this is because the hydraulic cutting radius of only 0.4m.The limited scope of lead slotted free gas content is low,only for local enhancement.