Oxidation Characteristics and Kinetics of Shale Oil Using High-Pressure Differential Scanning Calorimetry

Abstract

In situ combustion (ISC) has received much attention in the area of the development of shale oil reservoirs in recent years. The primary mechanism of interest for ISC is the oxidation kinetics of the shale oil with injected oxygen. In this paper, the oxidation characteristics of one shale oil collected from the Xinjiang oilfield were researched using high-pressure differential scanning calorimetry (HP-DSC). Then, the influences of quartz sand and shale detritus on the heat liberated of shale oil were analyzed. Subsequently, the kinetic parameters were determined using two iso-conversional models, Friedman and Ozawa-Flynn-Wall (OFW). The differential scanning calorimetry (DSC) profiles peaked at 317 and 454 °C with heat flows of 4.38 and 7.16 mW/mg, respectively, while the HP-DSC profiles peaked at 301 and 431 °C with heat flows of 32.6 and 7.92 mW/mg, respectively. This finding showed that the heat release yielded by shale oil oxidation was enhanced at 5 MPa compared to 0.1 MPa, especially in the low-temperature oxidation (LTO) region. The shale oil was subjected to a fairly higher heat release yielded by LTO rather than high-temperature oxidation (HTO) at 5 MPa, contrary to the DSC results measured at 0.1 MPa. The shale detritus could accelerate the oxidation reactions of shale oil. At the HTO interval, the activation energy was reduced apparently after the addition of shale detritus, suggesting that shale detritus generated a strong catalytic effect on reducing combustion difficulty. Therefore, it is believed that spontaneous ignition may be achieved during shale oil oxidation.