Mohave County miner., 1917-05-05
FACTS OF VALUE
 ID OIL DRILLERS
From rus.dnr,. Daily Miner,

the United States Geological Survey of the Department of the Interior has de- veloped some interesting facts which will doubtless be of considerable bene- fit to the oil industry. It has long been recognized that oil and gas are commonly associated with water, but of the chemical relation between the two little has been known. It is now possible, at least in California, accord ing to the survey, to estimate the pos ition of oil and gas, where present, from a chemical analysis of the water encountered by the drill. Thus in dril- ling a "wild cat" we'll an indication of the presence or absence of oil and gas below the water may be had by anay- king the waters excessively encount- cred, since investigations have deter mined that the deep-seated waters as sociated with oil in California fields are different in chemical composition from the waters found near the sur face as we'll as from the deeper waters outside of the oil fields. In some areas a significant change in composition may be detected as much as 1000 feet above the oil. In others the upper limit of alteration may be within few hundred feet of the oil.
 It is also possible to determine, at least in a general way, the source of the water flooding an oil well. In the Westside Coalinga field, for example, the horizon of the water may thus be determined rather definitely; in the Midway-Sunset field, where the dis functions are less sharp, the success of this method will depend largely on the number of authentic analysis that are available for comparison.
 In the oil fields of the San Joaquin Valley Water-bearing sands are gen erally encountered above, below, and in many places in the oil measures, and in these fields it is difficult to pre- vent the water, which may be under high pressure, from invading the oil sands and thus running a considerable tract of oil land. The United States Geological Survey accordingly detailed G. Sherburne Rogers to make study of water conditions in these fields, with special reference to the chemical character of the waters. Some of Mir. Rogers conclusions, drawn from a study of several hundred analysis of water from different depths, are as follows:
 1. Although some of the oi field waters are as salty as sea water, and are probably true fossil sea water, others are not even slightly salty to the taste. The distribution of salt is controlled by the freedom of circula- tion of the waters, which is governed chiefly by the geologic structure.
 2. Although the surface and shallow ground waters are strong sulphate or "gyp" waters, sulphate diminishes in amount as the oil measures are ap- preached and finally disappears. Out side the oil fields, however, large quan- titles of sulphate are found in even the deepest waters.
 3. The waters a short distance above the oil at many localities are sulphur waters" containing the gas hydrogen sulphide, but the shallow waters and those in the oil measures generally contain no sulphide.
 4. Carbonates, which are subordin- ate in the shallow waters, increase in amount as the oil zone is approached, and if no chlorides are present consti- ute the only dissolved salts in the waters associated with the oil.
 These conclusions appear to be we'll grounded for California, and probably hold for other arid regions in which the upper waters are sulphate or "alkali."
 The progressive alteration of the water as oil is approached is so con- stant and so striking in the area ex- amined that the conclusion that the oil and water reacted chemically can not be avoided. It was suggested long ago in the Russian oil fields that hydrocarbons are able to reduce sul- phate to sulphide, and that they them selves are simultaneously oxidized to carbon dioxide or carbonate. The re- action has not yet been checked in the laboratory, however, and though es- sentially correct is probably much |