Measurements And Analysis Of Activation Energy Calculated By Friedman Methods Under Different Pressure

The mechanism of ISC（in-situ combustion）underground is very complex.Many factors,as burning rate,are easily out of control.Kinetic parameters,such as activation energy,are key factors to predict reaction process in numerical simulations.It plays a very important role when investigate the reaction kinetics during ISC.Many investigators have deeply studied the measurements methods of activation energy of heavy oil combustion in porous media.However,little literature focused on the variation of activation energy with pressure,particularly when system pressure was much higher.According to the literature research,kinetic cell and gas analyzer are chosen as the reactor and recorder,respectively.This paper completes the calculation of activation energy under different pressure（pressure range from 0MPa to 2.5 MPa,temperature range from 25°C to 550°C）and analysis of main factors influent the calculated results by Friedman methods.Results show that:（1）higher system pressure leads to the higher effluent gas concentration in LTO（low temperature oxidation）and advanced reaction time;（2）the increasing of system pressure changes the activation energy especially in HTO（high temperature oxidation）,although the activation energy curve present the same trend in a certain pressure range;（3）when CO and CO₂ are produced in LTO,heating rate is correlated reciprocally with temperature during LTO（about 300°C）in the figure of ln da/dt¹/T-,resulting in the negative activation energy obtained;（4）both the shape of temperature curve and effluent gas concentration curve have a great impact on the accuracy of calculated results by Friedman method.