716 J. H. GARDNER THE MID-CONTINENT OIL FIELDS 



has pointed out the fact that the deeper a sand lies, beyond certain limits, 

 the more likely it is to be non-saturated with water. In such a case, if 

 a sand originally contained salt water and subsequently lost it, what was 

 the source of the present salt water in the sands around the oil and gas 

 fields? In this connection the writer leans to the possibility that the 

 present water is meteoric water ; that it has come into the beds from their 

 outcrop at the surface, working its way inward and downward through 

 the long period of time that has elapsed since crustal movements produced 

 the local structures and subsequent erosion brought the beds to outcrop 

 relatively near them. The loss of original connate water by capillarity 

 would leave more or less salt in the dry sands which the meteoric waters 

 would again absorb and become themselves salty. 



Water moving down the dip under a gradually increasing head would 

 gather the oil and gas that remained distributed through the sand and 

 push it forward and downward. At a local structure gas and- oil travel- 

 ing ahead would be caught until the moving water completely closed 

 around the ends of the ■ structure so as to completely trap the deposits 

 from farther movement ; water would hold them under hydrostatic head, 

 and in the case of gas force its absorption, so far as possible, in the 

 petroleum. In the case of only a partial saturation by water and slight 

 head, the oil and gas accumulations would not be perfectly gathered nor 

 held sharply under the structures, but the accumulations would lie on 

 milder types of folds, such as terraces and the heads of synclines, with 

 gas more definitely separated from the petroleum. Far down the dip, 

 where the hydrostatic head is strong, and consequently the saturation 

 more complete, only the reversed or closed structures, such as domes or 

 anticlinal bulges, would be sufficient to stop the onward movement of oil 

 and gas. It is true in the Mid-Continent field that the deep sands pro- 

 duce only in structures that show closed structure contours. The fields 

 farthest to the west in Oklahoma and Kansas, particularly where the 

 sands lie at depths below 1,800 feet, are situated on domes or bulges and 

 the surrounding portions of the sand are strongly saturated with brine. 

 Still farther down the dip the writer predicts that the oil sands will 

 eventually be found free from water, and that at some point between the 

 producing fields and the dry region there are relatively narrow, meander- 

 ing lines of petroleum and gas lying along the strike at the lower side 

 of the saturation. Here and there they may be encountered by a well, 

 but they are winding in shape like irregular coast lines, and too narrow 

 to be followed out profitably with the drill. The quantity of oil thus 

 concentrated would depend on the loss higher up the dip, also on the 



