The Mena weekly star., 1916-11-30

neither oil nor gas have been found under an anticline. It may happen that there are no sands or other porous rocks capable of holding oil under the anticline. Or it may hap pen if such reservoir rocks are present, nature has failed to en- rich them with oil and gas. It should be remembered that anti clnes do not form oil, but are sim ply the catehment basins for the ac- cumulation of oil and gas.
 More that 90 per cent of the anti clines so far drilled in Oklahoma and Kansas have been found to con- tain oil and gas.
 Are oil and gas found anywhere except under anticlines?
 Yes, in few cases oil and gas oc- eur in the earth wherever porous rock is held down by an impervious flne- grained cap rock. These sub stances sometimes occur along fault lines, under saline domes, near
 asalt or other igneous intrusons. in lenticular sands, or in cayerout limestoHes. A great majority of the oil fields of the world, however, and practically all in Kansas and Okla homa, are located along anticline folds.
 How Are Oil and Gas Formed?
 Nobody knows. Hundreds of chemists, physicists and geologists in varions lands have worked on the problem and 1t has never been definitely solved. A few scientists believe i'll the chemical theory, which holds the oil and gas have heen formed by the action of the supra heated steam on the earbides of certain metals, chiefly iron, much as ascetylin gas is formed when water is poured on calcium carbide. Most chemists and practically all eeologists, however, believe that oil and gas have been formed by he slow and long-continued distillatiOn of the organic parts of the plants and animals that were imbedded in the rocks at the time when they were laid down.
 What are the essentials of an oil and gas field?
 They are four, namely, source of supply, reservoir rock. a cap rock. and some form of structure which will hold the oil Whatever be the origin of oil and gas, there must be some source of supply, some rock in which the oil and gas have originated. Experience has shown that the source of supply is usually a ledge of limestone Many of the largest oil fields in the world obtain their supply either directly from heavy limestones, or within a short distance above such formations.
 The Reservoir Rock.
 A reservoir rock is also necessary in order to contain the oil. In the oil drillers parlanee, this reservoir rock is called an "oil sand be- cause 1t is usually a porus sand stone, which has been filled with oil. In some cases, however, the reser- yoir rock is a limestone, as for in- stance the Trenton limestone of Ohio and Indiana and the Tamasopa limestone of Mexico. The Wheel CT sand" of the Cushing field is limestone.
 A cap rock is the third essential. for there must be some substance to hold the oil and gas down and pre- vent their escaping This cap rock IS sometimes a hard brittle lime stone or dolomite. as for instance, the dolomite above the oil sand at Beaumont. Usually however, it is a soft, fine-grained clay or shale impervious to liquids, which pre- vents these substances from escap- ing.
 The fourth essential, and the one in which the oil geoloeist is partic- ularly concerned, is some form of structure which will cause the oil and gas to accumulate in a certain region. As stated above, the oil and gas are volatile and tend to rise to the surface. If there is any way by which they can pass upward thru the rocks. they will do so. and will soon be dissipated into the air. If they cannot escape the surface, they will at least find their way to the highest point in the rocks in which they are contained and will there accumulate This form of structure is usually an anticline.
 When GeOlOgist Fail.
 Can geologist always locate oil and gas?
 By no means Neither the geolo- glst nor any other living man can tell, with certainty. where oil. gas or other substance occurs beneath the earth All that the geologist can do is to locate the most promising place at which to drill. The drill IS the only sure oil-hnder
 What is the advantage of geologic al investigation2
 The geologist can minimize the risk. Only about to per cent of the wild eat wells located without geological advice, find oil or gas. Something between 90 and 70 per cent of tine wells located by geolo- gists find oil or gas. In other words, a geologist can charge a 95 per cent risk to a 10 per cent risk. but there IS always a risk in drilling. Dry holes are found in practically all de- veloped fields and only the drill can show what is under the ground.
 Are there any anticlines yet un- deiilnH in fllr abnr,aa o.,I Lro.,oo|c