Abstract
Description
Unconventional oil reservoir has presented the potential to become the significant source of hydrocarbon in the future productions. Many shale oil systems consist of nano-scale pores and channels, which are significantly smaller than those from conventional reservoirs. Such small size of the pore throats in shale may differ from the size of the saturating fluid molecules by only slightly more than one order of magnitude. This difference will result in different wettability, fluid flow mechanisms and storage capabilities in unconventional shale oil systems. However, the fluid flow behavior and saturation distribution in the nano-scale pores and channels is poorly investigated and understood. Therefore, it is increasingly important to investigate fluid flow behaviors and the fluids residue saturation in the nano-scale channels.
In this work, a lab-on-chip approach for direct visualization of the water/oil flow in nano-scale channels is developed by using advanced single-molecule imaging system combined with nano-fluidic chip. A comprehensive study of water/oil flow behaviors and the residue saturation distribution in nano-scale channels is presented.
Applications and Results
Most of laboratory experiments were conducted by using the shale samples where fluids flow mechanisms and residue saturation were difficult to measure during the experiments. In this study, the flow behavior and residual saturation of water/oil in nano-scale channels were investigated in the semi-transparent nano-fluidic chip. Flow patterns of water displacing oil and oil displacing water in 100 nm depth channels were characterized and compared with results in conventional-sized channels. Residue saturation of oil was obtained by the imaging data and the distribution of residue fluids in the nano-scale channels was analyzed.
Significance
This work demonstrated a novel visualization method for the characterization of water/oil flow properties in nano-scale channels of oil shale formations by using single-molecule imaging system combined with nano-fluidic chips. The results of the fluid transportations and residual oil/water saturations in nano-scale channels are considered to be very valuable for understanding the mechanisms of fluids transportation in unconventional shale oil system. This technique will provide important tool to enhance the oil production and evaluate the residual saturation in unconventional shale oil reservoirs.