Experimental Study On In-situ Mining Based Overheat Steam Convection Heating Oil Shale

In recent years, with the increasing consumption of oil energy in the worldand the increasing of oil demand, conventional oil resources are graduallyreduced. The products of pyrolysis of oil shale, as a kind of complementary andalternative energy, has get more of the world’s attention. The development of oilshale can not only solve the national demand for oil, but also can reduce thedependence on imported oil, and it is of great strategic significance. This papertake the superheated steam convection heating oil shale in-situ exploitationtechnology as the background, use the method of experiment, research on theproperties of oil shale pyrolysis, the rules of the oil/gas production under theaction of superheated steam,oil shale characteristics of pyrolysis and ruptureunder the combined action of superheated steam and simulated stress. The maincontents and results of this paper as follows：(1) Powder of Xinjiang oil shale samples and the samples pyrolyzed bysuperheated steam weight loss curve can be obtained by means of thermalgravimetric analysis, according to the weight loss curves, the followingconclusions are obtained: the process of pyrolysis of Xinjiang oil shale isdivided into three stages, the first stage is the evaporation of moisture withlonger duration and lower weight loss rate;the second stage is the pyrolysis of kerogen, the duration of this stage is shorter and the kerogen pyrolysis is violent,the weight loss rate is7%~11%; the third stage is the pyrolysis of inorganicminerals. The weightlessness rate of oil shale pyrolyzed by superheated steam isextremely low, compared with the low-temperature distillation technology,superheated steam is more effective. Both the pyrolysis temperature and theduration at the temperature have a great influence on oil shale weightlessnessrate, at higher temperature, the weight loss rate of pyrolysis is bigger, the longerthe pyrolysis continues, the weight loss rate is higher.(2) Utilized superheated steam boiler devised by Taiyuan University ofTechnology carried on simulating situ-mining pyrolysis experiment to the kindof oil shale are produced in Xinjiang. Oil shale gas production rule shale oilcollected product component characteristics were studied under the action ofsuperheated steam at different temperatures and the reason of oil shale gasproduction/oil production rules were analyzed in theory.The experimental resultshows:The main gas products produced by superheated steam pyrolysis oil shaleare organic gas products, hydrogen, carbon monoxide and the gas componentsare different at different time periods.Compared whit the low-temperaturedistillation technology, the shale oil obtained by superheated steam pyrolysis hasmore saturated hydrocarbons and normal paraffin hydrocarbon and lighthydrocarbon,the quality of shale oil is higher.(3) With the high temperature and high pressure superheated steam boilerdevised by Taiyuan University of Technology and the simulated stress system, the process of extraction of oil shale at in-situ stress state has been simulated:the first step is the process of fracturing specimen at the state of three axis stress,with the continuous injection of superheated steam and elevated temperature andpressure,The specimen is rupture at the perpendicular to the minimum principalstress direction, showing a multiple level fracture surface; then it is thepyrolysis process of oil shale in the specimens, oil and gas produced bypyrolysis with superheated steam flow out of the specimen in the flow process,at the same time,there will be a small amount of shale oil products attached tothe oil shale and concrete.(4) Based on CT experimental analyticl system, analysis of micro state ofsuperheated steam pyrolysis oil shale in-situ stress state.Oil shale the most closeto the region of heat injection is fully pyrolyzed, there are most hard minerals inthis oil shale and circular and elliptical holes in the mineral; mostly organicminerals are in the oil shale of middle area of heat injection, but there are cracksin the region of the oil shale and most of the cracks are dense and fine; mostlyorganic minerals are in the oil shale away from the steam injection hot zone, butonly there are a small amount of fissure as superheated steam circulationchannel.