investigation of auto ignition condition under different parameters

in this work, the potential of auto-ignition of heavy oil during in-situ combustion (isc) process was studied. kinetic studies were carried out using thermo gravimetric analyzer (tga), differential scanning calorimetry (dsc) and accelerating rate calorimetric (arc) techniques. effects of oxygen partial pressure, reservoir pressure and clay on auto ignition condition were investigated on a number of different heavy oil samples from south west iran mixed with silica sand or crushed carbonate rock and clay. based on the experimental results obtained by tga runs, the kinetic equation was derived for different oil samples in the presence of different sands. effect of partial pressure of oxygen in the injected air was studied. results showed that at atmospheric pressure, the peak of low temperature combustion (ltc) by producing co was initiated at 300 °c when air was injected. also, enriching the injected air by oxygen lowers the ltc by up to 50 °c. when the experiments were extended to reservoir pressure of 1300 psi, it was found that activation energy in the ltc region was lowered. as a result, initiation of ltc was started at 115 °c when air was injected. the dsc experiments, under non-isothermal condition showed that increasing the oxygen partial pressure resulted in more heat being evolved during the high temperature combustion reactions. also, the effect of clay as a catalyst was studied and it was found that the activation energy decreases considerably when clay is present in the system. the decrease in activation energy was from 359 to149 kj/gmole for one sample.