Tar mitigation using insitu heat generation chemicals (part I): A comparative study

Tar is an extra-heavy oil with ultra-high viscosity. Accumulation of tar in a reservoir ultimately results in production decline. This study represents the first part of the series of investigation, which aim at developing an insitu heat generation scheme (through thermochemical reaction) for tar mitigation to improve oil production from tarmat-impacted reservoir. Comparative studies have been conducted through both coreflooding experiments and field scale numerical simulation for tar removal using injection of thermochemical fluids (TCF) at 90 °C and other fluids, including water (23 °C), hot water (90 °C), oil soluble organic solvent sludge (90 °C) and steam (210 °C). The results from coreflooding experiments revealed that TCF injection has comparable removal efficiency in terms of recovery factor (RF = 93%), with that of steam injection (RF = 94%). In comparison, the RF from water, hot water, and injection of an oil-soluble solvent sludge are 21, 53, and 85%, respectively. From the field scale simulation, the results affirmed greater efficiency of TCF injection over steam injection with higher tar recovery rate, recovery factor (RF), and Oil: Steam ratio (OSR). In addition, the simulation results revealed that cyclic injection of TCF outperformed continuous injection operation.