Do Shale Pore Throats Have a Threshold Diameter for Oil Storage?

Abstract

In this work, a nanoporous template with a controllable channel diameter was used to simulate the oil storage ability of shale pore throats. On the basis of the wetting behaviours at the nanoscale solid-liquid interfaces, the seepage of oil in nano-channels of different diameters was examined to accurately and systematically determine the effect of the pore diameter on the oil storage capacity. The results indicated that the lower threshold for oil storage was a pore throat of 20 nm, under certain conditions. This proposed pore size threshold provides novel, evidence-based criteria for estimating the geological reserves, recoverable reserves and economically recoverable reserves of shale oil. This new understanding of shale oil processes could revolutionize the related industries.

Correlative multi-scale imaging of shales: a review and future perspectives

“…Ambrose et al (2010) used imaging datasets to build kerogen and pore networks from which gas-in-place volumes were calculated. Quantification of the 3D geometry and topology of pore pathways can be built on basis of segmented pore, and gas transport could be analysed from the development of pore network models (Keller et al 2011;Zou et al 2015) (Figure 10…”

Turtles and Snakes: Evidence for Molecular Shape-Selective Migration of Crude Oil Hydrocarbons in the Bakken Petroleum System

“…The molecular size of oil hydrocarbons can have significant effects on how hydrocarbons interact with the source and reservoir rock matrices in unconventional systems, simply because unconventional reservoirs (like the Bakken Petroleum System) have very low (<0.1 millidarcy) permeabilities and pore throat radii of only a few nanometers, that is, pore throat sizes which approach the molecular size of crude oil hydrocarbons. − Several laboratory and modeling studies have shown that molecular-size-based “sieving” occurs during the secondary migration through tight reservoir rocks because of the ability that lighter (lower molecular weight) hydrocarbons have to access smaller pores than the heavier (higher molecular weight) hydrocarbons simply by steric size exclusion. ,− The retention of lighter hydrocarbons more than heavier hydrocarbons is a process similar to size-exclusion chromatography where the lighter hydrocarbons are selectively retained during oil migration simply by their ability to access smaller pores in the rock matrix than the heavier hydrocarbons . Modeling studies also show that the same molecular size filtration mechanism influences the distribution of different-sized hydrocarbons in reservoir rock pores that have nanometer-range pore throats with the result that the heavier hydrocarbons are primarily present in the larger pores (hundreds of nanometers in diameter), while the lighter hydrocarbons dominate the smaller pores (tens of nanometers in diameter) and that oil is primarily produced from the larger pores (e.g., >200 nm). − …”

Long-Time-Period, Low-Temperature Reactions of Green River Oil Shale

“…The change in going from powder to chunks is much larger than the increase in external surface area of the particles consequent on grinding and must therefore be due to opening of blocked pores during grinding. It is believed that after the intraparticle reactions noted above much of the reaction product resides in the smaller pores of the oil shale , and is then released by vaporization or otherwise. It would then be expected that the surface area and pore volume would increase as the product was released from the shale and it was indeed found that the pore volume of the THF-insolubles, ground to a similar particle size to the shale powder, was higher than that of the shale powder.…”