Interfacial and Wetting Properties in Shale/Methane/Water and Shale/Methane/Surfactant Systems at Geological Conditions

Abstract

Understanding surface properties such as wettability and CH4/shale interfacial tension (IFT) is essential to decipher CH4 productivity and hydrocarbon-in-place estimates. However, these factors are poorly understood due to lack of data despite their importance. We thus measured the equilibrium contact angle (θe), reflecting the degree of wetting for shale/CH4/water systems, and determined the governing interfacial tensions. In particular, water/CH4, water/shale, and CH4/shale IFTs are determined at pressures 0.1, 5, 10, 15, and 20 MPa and temperatures 303.15, 323.15, 343.15, and 373.15 K. Shale samples from Eagle Ford and Mancos were used to examine the effect of treating the shale samples with cetyltrimethylammonium bromide (CTAB, a cationic surfactant) on contact angle and IFTs. Finally, excess CH4 adsorption on the shale surfaces was determined before and after adding CTAB surfactant. The results showed that shale/CH4/water equilibrium contact angles (θe) increased with pressure but decreased with temperature. The Eagle Ford sample exhibited a contact angle of 138°. In comparison, the Mancos shale sample exhibited 97°, at both 20 MPa and 373.15 K. These contact angles suggest that Eagle Ford shale is more CH4-wet than Mancos shale due to the higher TOC of Eagle Ford shale (4.95 wt %, while Mancos shale had a TOC = 1.02 wt %). Water/CH4 IFT decreased from 71.47 to 56.02 mN/m as pressure and temperature increased from 0.1 MPa and 303.15 K to 20 MPa and 373.15 K. Shale/CH4 IFT also decreased with increasing pressure and temperature. Finally, CTAB surfactant treatment increased contact angles but reduced water/CH4, water/shale, and CH4/shale IFT. CTAB also reduced the amount of adsorbed CH4 and increased the amount of free CH4, which implies improved CH4 recovery from shale reservoirs. These results provide new insights into the first-principles that govern CH4 recovery from shale reservoirs.

Molecular Simulation of Methane Adsorption in Deep Shale Nanopores: Effect of Rock Constituents and Water

“…Previous studies of microscopic water distribution in minerals [17,18] and organic matter [15,19] have demonstrated the strong hydrophilicity of clay minerals and the mixed wettability of organic matter. Extensive experiments [20,21] and molecular simulations [18,22] have shown that water can significantly reduce the methane adsorption capacity in shale pores, with mechanisms including adsorption site capture, pore space occupation, and methane partial pressure reduction [15,19,23]. Previous studies of methane adsorption in water-bearing shale pores have mainly focused on the influence of water on methane adsorption and its mechanisms.…”

Novel Nanocomposite Coated Proppants for Enhanced Scale Inhibition Lifetime in Tight Shale Formations

“…The significant increase in energy demand, along with the depletion of conventional wells, has prompted considerable interest in exploring and developing unconventional oil and gas reservoirs . Unconventional hydrocarbon reservoirs, such as shales, possess low porosity, ultralow reservoir permeability, poor connectivity, and non-Darcy flow. − The current development of unconventional oil and gas reservoirs relies significantly on horizontal drilling processes in conjunction with hydraulic fracturing. The recovery of hydrocarbons from shale and other unconventional formations has been justified to be economically feasible due to such stimulation techniques.…”

Virtual Special Issue of Recent Advances in Shale Gas Exploration and Exploitation

“…There are six original contributions and two reviews on this topic. Abdulelah et al 15 measured the interfacial and wetting properties in shale/methane/water and shale/methane/surfactant [cetyltrimethylammonium bromide (CTAB)] systems at geological conditions. They also measured excess CH 4 adsorption on the shale surfaces before/after treating with CTAB.…”