Research On Characteristics And Fire Control Technology Of Oil Shale In Haishiwan Coalfield

Haishiwan coalfield in Basin Minhe is a deposit that has various mineralresources, not only owns ample coal resources, but also oil shale and possesses oilsand and other resources. Self-mining of oil shale seam is influenced by two factors,the mining effect of extremely thick No.2coal seam below, and the seepage oil gasfrom oil sand above. Taking oil shale in Haishiwan coalfield as the research object,carries out enrichment state and distribution regularity, multiple physical parametersof oil shale, and the mining effect of No.2coal seam on the oil shale seam above.Based on these analyses, the three elements are discussed which are the possibility ofcausing fire disaster of oil shale working face. And how to prevent the type of firedisaster is provided. And the main conclusions are drawn below:(1) The sapropelitic group dominates the mainly content of organic maceral ofoil shale in Haishiwan mining area. The vitrinite reflectance Ro,maxof the oil shale arebetween0.542%and0.635%, and have low metamorphic grade, the organic carboncontent of which ranges from27.8%to38.6%, and have rich organic matter, and anaverage oil ratio of which is17.0%, and have a good quality. And It shows that oilshale of Haishiwan coalfield is a low ash content, high quality and low sulfur contentshale. Besides, considers that the combine effect of the geological structure,depositional environment and paleoclimate characteristic influence on theminerogenetic condition of oil shale seam in Haishiwan mining area.(2) Based on the gas adsorption method, the result is gotten that the pore with adiameter less than10nm dominates the pore volume and specific area of oil shale.And there is a positive relationship between organic carbon content and the volumeand specific area of micropore and mespore of oil shale, because the organic matter isa the main factor that affects the pore structure. The hysteresis loop obtained from theN2adsorption test revealed that the main pore shape of oil shale is a type of narrowflat plate and also includes some irregular pores. The adsorption constant a rangesfrom6.49m3/t to7.71m3/t, and rising with the organic matter of oil shale. Becausethe organic matter of oil shale is the carrier of micropore that can provide moreadsorptive position for gas.(3) The numerical simulation results show that the plastic failure of jambbetween the goaf of oil shale seam and the workface of No.2coal seam is due to themining activity at both sides of it. The destruction of jamb makes a fracture tunnel that can result in gas transfer and thermal conduction and convection. Oil gas from oilsand overlying oil shale can flow into the goaf along these fractures. With the fallenoil shale together, they will become a potential combustible in goaf of oil shale seam.It forms the condition of oxygen, heat source and combustible that three elementssurvive together, then goaf of oil shale seam easily catch fire.(4) Based on those analyses above, fire prevention plan for oil shale workfacewas drawn. Firstly, for eliminating the influence of extremely thick No.2coal seam onoil shale seam, Protective workface (oil shale seam) should be mined ahead ofprotected seam workface (No.2coal seam) one or two workface zone in the inclineddirection, and ensure sufficient leadtime. Secondly, for removing the combustible ofoil gas, the distribution of oil sand should be advanced detected, meanwhile need totake measures for pumping oil gas. Thirdly, for forecasting the spontaneouscombustion of oil shale workface in early stage, gas monitoring means for goaf of oilshale seam should be reinforced. At last, for reducing the air leakage and restrainingthe oxidation rate of combustible, goaf of oil shale should filled with yellow mudmaterial along with mining activity.