Experiments and simulations on factors affecting the stereoscopic fire flooding in heavy oil reservoirs

Abstract

In-situ combustion (ISC) or fire flooding (FF) technology had been widely applicated in developing heavy oil reservoirs. Due to the complex physical and chemical processes, it is not easy to guarantee the high oil recovery. For thin layer reservoirs, vertical well mode of FF can achieve good results, but for thick layer reservoirs, the vertical producing degree of FF under vertical well pattern is low. Therefore, it is necessary to deepen the basic understanding of fire flooding under different well patterns and study the influencing factors for thick heavy oil reservoir. Stereoscopic fire flooding (SFF) mode is proposed in this paper, and the one-dimensional combustion tube and differential scanning calorimetry (DSC) experiments were introduced and designed. The heavy oil samples of G block in Liaohe oilfield in China were studied and the oxidation kinetic parameters were obtained by experiments. The applicability of oil samples for fire flooding was tested. The different fire flooding modes was compared and the influencing factors of SFF were analyzed through simulations. The results indicated that the temperature of high temperature oxidation (HTO) was above 450 °C. The CO2 content of the produced gas was more than 13% and the apparent HC atomic ratio was 1.28. DSC experiments showed the activation energy of HTO stage was 1.40 × 105 J/mol. The results indicated that the heavy oil samples can reach a high temperature combustion state. The SFF mode was simulated by CMG-STARS module based on the experimental results. The simulation results showed that SFF had better performance than FF of only vertical wells in oil recovery. The important factors of SFF, such as gas-injection rate, reservoir thickness, transverse permeability, vertical permeability, crude oil viscosity, formation dip angle and relative position of horizontal wells and the applicable conditions of SFF mode were analyzed and the optimum condition for SFF mode for each influencing factor was analyzed, and the conclusions were obtained.