THERMOGRAVIMETRIC STUDIES OF SYSTEMS PERTINENT TO THE IN-SITU COMBUSTION PROCESS FOR ENHANCED OIL-RECOVERY .1. DEVELOPMENT OF A HIGH-PRESSURE THERMOBALANCE

A high-pressure (0-1000 psig) thermobalance experiment has been develo ped in order to obtain thermogravimetric (TG) and derivative thermogra vimetry data (DTG) pertinent to the in-situ combustion process for enh anced oil recovery. Studies on the pressured thermo-oxidative behaviou r of 20/80 (W/W) oil/sand and coked sand samples are reported. In the case of the oil/sand sample under a 100 psig non-oxidising atmosphere, distillation/evaporation occurred below 320 degrees C at which point thermal cracking commenced. Above 520 degrees C only carbon-rich coke material remained. Under an oxidising air atmosphere at 100 psig, the TG curves were more complex. Below 360 degrees C, low-temperature oxid ation (LTO) competes with distillation/evaporation; hence the rate of weight loss is significantly decreased whilst fuel deposition occurs. Between 360 degrees C and 475 degrees C, the observed weight loss is b elieved to be due to a combination of hydrocarbon combustion and visbr eaking or coking. Above 475 degrees C, combustion of the remaining org anic matter (high-temperature oxidation HTO) occurs. Experiments condu cted using coked sand samples showed that, in air at 100 psig, the sam ple weight increased up to 250 degrees C, This is attributed to the fo rmation of oxygenated species. Above 250 degrees C, the sample rapidly lost weight due to combustion reactions.