Soil Wettability As Determined from Using Low-Field Nuclear Magnetic Resonance

Abstract

The molarity of ethanol droplet and water drop penetration time methods are commonly used to determine soil wettability because these tests are quick and easy to perform. However, these tests do not provide reproducible results on the same sample. Low-field nuclear magnetic resonance (NMR) is shown as an alternative tool to determine soil wettability. Addition of small amounts of water in dry wettable porous media produces predominant amplitude peaks at transverse relaxation times (T2) of 100 ms or less while addition of water in dry water-repellent porous media with the same pore structure produce predominant amplitude peaks at T2 values near 1000 ms. The geometric mean of T2 (T(2gm)) from water-repellent samples immediately after the addition of water is greater than 1000 ms, which is close to that of bulk water, while T(2gm) from wettable samples immediately after the addition of water is significantly less than 1000 ms. Measurements over time show that water-repellent samples eventually reach the same equilibrium end point as its corresponding wettable sample when continually exposed to water. This paper will show that NMR can be used to formulate a screening criterion for quickly determining wettability. The advantage of using NMR is that the results are reproducible provided the sample is prepared and analyzed in a systematic manner.

NMR relaxometry and diffusometry in characterizing structural, interfacial and colloidal properties of heavy oils and oil sands

“…The positions of the peaks in the T 2 relaxation spectrum have been used to determine the wettability, wettability alteration and water uptake of soil and sand cores [21,61]. Water in preferentially water-wet samples was shown to have T 2 peaks around 100 ms or less.…”

NMR wettability indices: Effect of OBM on wettability and NMR responses

“…They found that water relaxed faster in the water-wet system than in the oil-wet system. Later works (Devereux, 1967;Saraf et al, 1970;Williams and Fung, 1982;Borgia et al, 1991;Hsu et al, 1992;Howard, 1994;Straley et al, 1995;Daughney et al, 2000;Zhang et al, 2000;Al-Mahrooqi et al, 2003;Manalo et al, 2003) confirm that NMR technique can give qualitative information about wettability. However, the quantitative connection between wettability and NMR characteristic parameter has been investigated by only a few studies (Howard, 1998;Guan et al, 2002;Fleury and Deflandre, 2003).…”

H-NMR Relaxometry to Monitor Wetting and Swelling Kinetics in High-organic Matter Soils

“…They also showed signs of a possible swelling of organic matter and of changes of the relaxation times of water during the first days of swelling. Langford et al (2002), Manalo et al (2003) and Todoruk et al (2003a, b) used H-NMR-Relaxometry to determine and understand soil wettability. A detailed discussion of their NMR data would be of particular relevance, because appropriate independent validation methods are not yet available.…”