Abstract

The hydrodynamic thickness δ of adsorbed petroleum (crude) oil layers into the pores of sandstone rocks, through which the liquid flows, has been studied by Poiseuille's flow law and the evolution of (electrical) streaming current. The adsorption of petroleum oil is accompanied by a numerical reduction in the (negative) surface potential of the pore walls, eventually stabilizing at a small positive potential, attributed to the oil macromolecules themselves. After increasing to around 30% of the pore radius, the adsorbed layer thickness δ stopped growing either with time or with concentrations of asphaltene in the flowing liquid. The adsorption thickness is confirmed with the blockage value of the rock pores' area determined by the combination of streaming current and streaming potential measurements. This behavior is attributed to the effect on the disjoining pressure across the adsorbed layer, as described by Derjaguin and Churaev, of which the polymolecular adsorption films lose their stability long before their thickness has approached the radius of the rock pore.

Graphical abstract

After increasing to around 30% of the pore radius, the adsorbed layers thickness δ stopped growing either with time or with concentrations of asphaltene in the flowing liquid.

Full-size image (4K)

Keywords: Hydrodynamic thickness; Electrokinetic measurements; Streaming current; Streaming potential; Zeta potential; Disjoining pressure; Asphaltene; Permeability; Porous medium

Article Outline

1. Introduction

2. Methods

2.1. Electrokinetics of rock cores

2.2. Poiseuille's equation

3. Experimental

4. Results and discussion

4.1. Surface potential of rock cores under adsorption layers

4.2. Hydrodynamic thickness in rock pores

4.3. Formation and deformation of adsorbed layers

4.4. Capillary condensation in narrow pores

5. Conclusions

References