A Method for Determining the Water Content of Sands

A knowledge of the water content of producing sands is becoming ofincreasing importance to the petroleum industry. It is now a generally acceptedfact that practically all oil sands contain some free water. Recent experimentshave shown that an appreciable fraction of the pore space of a sand may befilled with water while oil production from this sand is water-free. Crowtherand Haines, in experiments on electroendosmosis in soils, reported that therewas no endosmotic flow of water when the moisture content of the soil was 14per cent or less, indicating that the moisture content of the soil below 14 percent was held by different forces than the water content above this value. Thisresult is confirmed qualitatively by Dunlap, who found that "as the volumeof water in the voids exceeds approximately 15 per cent of the pore volume, thepermeability of the core to kerosene is markedly reduced." The author hasalso found in other experiments that the gas flow through a water-saturatedsand reaches essentially 100 per cent when the pores of the sand still containfrom 10 to 15 per cent water. The velocities of the flowing fluid in theexperiments cited were comparatively high, so that in practice one may expect, at lower fluid velocities, an even higher moisture content of the sands withwater-free oil or gas production. Thus a knowledge of the water content ofoil-field sands becomes of considerable importance in estimating petroleum andgas reserves, and efficiency of fluid recoveries from depleted reservoirs. Rapid and reasonably accurate methods of measuring the water content of sandcores have not been described so far in any literature that has come to ourattention. The method described below is developed from methods that have beenused for some time to measure the water content of alcohols. It is anapplication of the fact that in the presence of certain organic liquids such askerosene, carbon tetrachloride, xylol, etc., water and alcohol are only partlymiscible. T.P. 972