Influence of reservoir rock and fluids on crude oil oxidation using an accelerating rate calorimeter

Air injection is a very promising technique for improved oil recovery from deep, light oil reservoirs that have been previously water flooded-with the proviso that all of the oxygen can be removed by reaction with the crude o il. A high pressure accelerating rate calorimeter (ARC) has been used to fo llow the adiabatic exotherm obtained when oil reacts with air, and when res ervoir rock and water are present. The experiments were conducted on four l ight crude oils, starting at the respective reservoir temperature. The very sensitive ARC apparatus is able to automatically follow the self-heat rate adiabatically, closely simulating conditions in an actual reservoir, but i n a batch manner, i.e. closed 'bomb'. The exotherms obtained generally exhi bit two regions. First, a low temperature oxidation (LTO) region, extending up to about 250 to 300 C, followed by a high temperature oxidation (HTO) r egion, which can extend up to 500 C, or more. The individual exotherm chara cteristics of each oil depend on the physical and chemical properties as we ll as the associated reservoir rock and reservoir fluid. The 'fast' exother m observed for oil and air alone, is modified substantially in the presence of reservoir rock and water due the heat capacity of these materials. The measured exotherms enable suitable reaction rate models for the oil oxidati on kinetics to be derived, which can be used in reservoir simulation studie s.