Evaluation of kinetics and energetics of thermochemical fluids for enhanced recovery of heavy oil and liquid condensate

An innovative approach in enhancing oil and gas recovery is the in situ heat generation through exothermic chemical reactions using thermochemical fluids. This study presents the kinetics and energetic analysis of typical thermochemical fluids (NH₄Cl and NaNO₂) and preliminary evaluation of performance in recovery of heavy oil and gas condensate. As a committed step toward understanding the performance of the fluids, the reactions between the fluids (with and without hydrocarbon fluids-heavy oil or liquid condensate) were monitored in a microreactor under different operating temperatures (T_r ≈ 20, 40, 55, and 75 °C) in a close system. The data obtained were used in evaluating the kinetic behavior of the system. Core flooding experiments were also conducted for evaluating the recovery of the gas condensate and heavy oil. Analysis of kinetics and energetics of the system shows that the change in temperature Î"T and the enthalpy change Î"H of the system due to heat generation were ≈88 °C and ≈369 kJ mol^-1, respectively, regardless of the operating temperatures T_r. However, the time to reach peak conversion during the reactions was observed to reduce from 1064 to 382 s as the operating temperature increased from 20 to 75 °C. Accordingly, the rate constant K_r (s^-1) increased from 0.0013 s^-1 under ambient conditions to 0.0156 s^-1 at T_r = 75 °C. The reactions were all first order and have been estimated to have the activation energy E_a ≈ 35.5 kJ mol^-1 within the operating temperatures. Moreover, basic applicability of the chemical in condensate recovery (63% at injected PV of 2.1) as well as in the recovery of heavy oil (72% recovery, by injecting 1PV of the chemical) has been confirmed.