Temporal and spatial temperature distributions and heavy oil production performances in hot-water flooding processes at different water temperatures and injection rates

Abstract

The petroleum industry becomes more and more interested in applying some low-heat thermal-based enhanced oil recovery (EOR) processes to recover heavy oils due to their much-reduced energy consumptions, greenhouse-gas emissions and project costs in comparison to other thermal-based EOR processes, such as steam flooding (SF) and steam assisted gravity drainage (SAGD). In this paper, the heavy oil production performance of hot-water flooding (HWF) as a typical low-heat thermal-based EOR process for reducing the viscosity of heavy oil and improving its mobility was experimentally studied by using a 1-D cylindrical sandpacked physical model with the porosity and permeability of 35.0 % and 4.50 mD, respectively. A total of eight coreflooding tests with different injected water temperatures from 20 °C to 90 °C and injection rates from 0.5 cc/min to 5.0 cc/min were conducted to compare seven HWF tests and one conventional waterflooding (WF) test. In particular, the transient temperature vs. time data were measured at five different locations in the physical model during each HWF/WF test by using a high-precision thermocouple probe with five sensors. The measured in-situ temperature vs. hot-water (HW) injection time/volume data in the HWF tests at a low HW injection rate exhibited three distinct periods. Period I had a progressive increase in the temperature, which was followed by Period II with a decrease in the temperature and Period III at a stable temperature. The transition from Period I to Period II indicated possible HW breakthrough (BT). In contrast, the measured in-situ temperature was always increased with the HW injection volume in the HWF tests at the medium to high HW injection rates. It was found that the heavy oil recovery factor was always increased as the ambient temperature and HW temperature were increased. However, the HW injection rate needs to be optimized due to its dual opposite effects on the heavy oil production performance of HWF. Overall, HWF is found to be an effective low-heat thermal-based EOR process in the heavy oil reservoirs, in comparison with the traditional WF.