AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Heavy-Oil Recovery in Innovative Reservoir Micro-Models: A Comparison Between Heat and a Cost-Effective Additive on Oil Recovery
(1) Geology & Petroleum Geology, University Aberdeen, Aberdeen, United Kingdom.
Laboratory testing of heavy oil recovery from porous media is problematic because of the high viscosity oil and poorly consolidated reservoirs. For similar reasons geological characterisation of the rock is challenging. Cost-effective chemical additives that enhance the mobility ratio of heavy oil provide new challenges for reservoir characterisation as higher oil recovery affects physical integrity. A better visual and quantitative understanding of the displacement of heavy oil with and without chemical additives is possible using innovative synthetic rock samples that are prototypes for using heterogeneous geological materials. Synthetic rock is built behind a gap-filter etched within a microfluidic channel. Fluids enter the device via glass capillaries bonded to the glass slide. Tap and sea water were used as displacing fluids and a ~10,000 cp oil was used as a reservoir fluid.
Core floods were carried out on the samples that tested displacement efficiency using cold and heated (up to 95 deg C) water with or without chemical additives. Because the samples are translucent, the heavy oil is dark and the water clear water saturation (Sw) is estimated visually and So (oil saturation) = 1 - Sw is estimated by point counting digital images obtained during the core floods. Chemical additives (5 ppm concentration used in these experiments) and thermal energy typically result in 35-40% increase in recovery for heavy oil than using cold water.
Large volumes of water are problematic to handle during oil production and the unfavourable mobility ratio (M) of heavy oil and water exacerbates this. Estimation of M from experiments with the synthetic samples is made by measuring the fractional water-cut and allows direct comparison with independent data. The experimental results are consistent with general models for two-phase flow in porous media. Heavy oil recovery using the chemical additive (5 ppm) was similarly efficient to thermally induced (>85 deg C) heavy oil recovery and on the basis of our experiments offers an alternative technology that has the potential to raise the levels of heavy oil recovery in line with light oils without the energy requirements needed for heating. The synthetic samples offer a cheap and rapid solution that provide data very similar to special core analysis and have broader applications to the dynamic physical simulation of reservoirs and their fluids, particularly interactions between fluids and key reservoir rock components.