Show hints H ints on 0 n prospecting prospect ng for oil there ire re only a few kinds of true surface indications of petroleum and most of them are easily recognized in regions where oil has not been proved to exist either oil gas or some bituminous substance that once was oil is the only reliable indication of its presence oil may seep from a porous bed or ooze from joints in the rocks or it may issue with water at some small spring or may form a film on pools in swamps or meadows or in water wells at most such seepages see pages the oil escapes in but small quantities yet the rainbow hued film it spreads on water and its odor are almost certain to attract attention these and other hints for the oil prospector are suggested by K C heald an oil geologist of the united states geological survey in some places oil fills the pores or a part of the pores of a bed of rock that appears at the surface but it does not flow it may appear as tarry patches on the face of the rock or it may emit an odor particularly ticul arly on hot days the weathered surfaces of the rock in many such oil soaked beds however do not emit an odor nor do they show any indications of oil oil although when the rock is broken its fresh surfaces may fairly reek of petroleum some such rocks give no odor of oil even when freshly broken but when they are subjected to simple chemical tests they yield traces of oil bitumen or paraffin in the california oil districts beds of burned or shale are almost as significant of the presence of petroleum as ol oil saturated beds at some places the shale was saturated with oil that seeped from underlying beds and was then in some way ignited and baked into a brick red to bright cherry red mass ranging in hardness from that of soft building brick to that of almost glassy slag the california oil region is the only known place in the united states where such burned indicate the probable occurrence of oil although have been similarly baked in other regions region s by burning coal beds that lie near the surface how to sample escaping gas escaping gas may indicate oil but the gas is usually almost unnoticeable except where it rises through water in bubbles to the surface As some kinds of ga gas are not associated with oil escaping gas should be sampled and analyzed if the gas escapes in large quantities it may be tested with a match practically all the gases that are commonly associated with oil will burn the odor of the gas is also an indication of its character one of the commonest gases that do not indicate the presence of petroleum is hydrogen sulphide which smells like rotten eggs the only sure way to learn the true nature of the gas is ig to have it analyzed A 2 quart sample is enough for analysis the samples may be taken in a 2 quart bottle or in two 1 quart bottles through a large f funnel the bottle must be thoroughly cleaned with hot water without soap if the gas is bubbling up through water the bottle should first be filled with clean water and it should then be held below the surface neck down with the funnel inserted in its neck and held or guided over the bubbling gas the gas will then enter the bottle through the funnel and displace the water which will be forced out of the bottle when no more gas can get into the bottle and while the bottle is still inverted under water the tunnel funnel should be withdrawn and a new tightly fitting cork should be jammed firmly into the bottle without tipping or tilting it if the seepage is not under water a sample of the gas can be taken by building clay around and over the escape so that a part of the gas shall come out of an opening that can be covered with the large end of a big funnel clay should be packed tightly around the edge of the funnel so that the gas will enter the funnel and pass out of its tip A bottle should be inverted over the tip of the funnel for about 20 minutes and then gently lifted off without tilting and tightly corked characteristic surface showings in some places large quantities of oil have escaped to the surface and formed deposits of asphalt or other bituminous substances such deposits indicate that oil once existed in the region and that the region is worthy of careful study but they are not a certain indication of tho the presence of petroleum tor for all the petroleum may have escaped to the surface or it may have been altered to some bituminous substance from which oil can not be extracted in some regions salt water springs sulphur water springs gypsum rock salt and sulphur are associated with oil off on the gulf coast of texas and louisiana gypsum or rock salt on the surface or in water wells may indicate the presence of oil as the oil fields of that region are commonly associated with salt domes that contain great masses of salt and gypsum these minerals however occur also in abundance in regions where no oil has been found and where it can not possibly exist false signs and oil indications many things are frequently referred to as indications of oil which have no connection whatever with it probably the most common of these is the rainbow color ed film produced on water by iron oxide or manganese oxide or by decaying animal or vegetable matter this film can easily be distinguished from the film produced by oil for it has no smell of petroleum and it is brittle whereas an oil film is tough an oil film when stirred will become streaked with colored bands that double and twist about but do not break apart and any openings that are made in it have smooth edges which are likely to draw together rainbow films that do not indicate oil will break into separate patches when stirred and the patches are not likely to join again into one smooth sheet these little patches have edges with sharp corners and many of them are divided by narrow cracks that show no tendency to close it is often said that a country looks like oil that is the surface gives the speaker the impression that it must be underlain by oil this remark means only that the country looks like some other oil pro region which the speaker has visited the surface appearance of a region however means absolutely nothing as indicating the presence of oil for oil may occur under a surface of any kind from the orange groves of california to the alkali plains of wyoming from the ice encircled hills of alaska to the sun blistered table lands of utah and similarly in many regions where the surface is of exactly the same type as that in certain oil fields there is not a drop of oil some men declare that a guide to oil may be found in the vegetation tho the trees bushes grasses and flowers but oil is found as abundantly in the treeless plains of kansas or tha gulf coast as in the pine covered ridges of pennsylvania and west virginia or the blackjack and hickory covered hills of oklahoma even in a region that is known to be oil bearing and in areas having the most promising geologic conditions a positive statement that oil in paying quantity is sure to be found in certain areas is not justifiable although in some such areas the chances are ten toone that it will be found oil finders and oil witches in spite of all these facts some men who call themselves diviners dividers div iners oil finders oil witches and other names suggestive of unusual powers pretend to be able with or without the assistance of instruments to detect unfailingly the presence of oil in paying quantity nearly all the methods employed by these men are based ba sed upon superstition or upon some supposed supernatural practice just as were the methods of the old time al chemists who claimed the power to change lead iron and other base metals to gold some of these oil witches simply use a forked stick like the peach tree twig or the hazel wand of the water witches others have elaborate instruments fitted with magnets and coils supposed to work through magnetism or provided with parts made of platinum gold silver copper lead iron or some other metal supposed to work through affinity of metals these men are usually ready to prove the correctness of their guesses with somebody alses money but there is hardly a record of an oil witch risking his own money on his certain knowledge and of the thousands of devices tested not one has proved to be of the slightest value as a means of finding oil now and then of course oil is struck at a place chosen by the use of one of these devices for in a region where oil may exist occasional success in finding it by any means is inevitable A great many of the best oil fields in the united states were found by blind random drilling with no attempted guidance either scientific or supernatural As one sagacious old driller remarked even a blind pig rooting for nuts is bound to find some if there are plenty of them and he hunts long enough some erroneous beliefs A number of erroneous popular beliefs about the occurrence of oil deserve particular mention it is sometimes said that oil occurs below the surface of the ground in some regions just as water does in others this would mean that a well in an oil region is as likely to strike petroleum as a well in a water bearing region is likely to strike water that the oil is distributed in an almost continuous sheet beneath extensive parts of the country this is not true another statement tat ement frequently heard is that the oil forms an underground stream and that a lucky location for a well must lie over the stream expensive and fruitless drilling has repeatedly shown that such streams of oil do not exist A belief that is strongly held in some parts of the country is that oil pools are connected that some channel connects the pools in an oil region this belief is absolutely disproved by the ranks of barren wells that ancl encl encircle acle practically every producing oil pool in the world another wrong idea is that petroleum occurs in underground ponds or lakes in fact pros es of some oil companies refer tto to I 1 lakes and rivers of oil giving the idea of great caverns filled with oil not a single such cavern has been found in any oil field in the united states oil is really contained in the tiny openings between grains of sand in the pores and crevices of a crystalline limestone or as in the largest wells in the comparatively small openings of a very porous rock properties of petroleum petroleum always occurs as a liquid its more volatile parts may be taken into the air by evaporation or into dry clays by absorption but the solid or semisolid semi solid substance that remains is not called petroleum but is known as asphalt or or by the more general term bitumen although all are liquid they differ in their qualities in fact two from different districts or even from different levels in the same well are seldom exactly alike either in appearance or in value they may differ notably in color by reflected light as seen in a pail or other container oil is commonly green but it may be any one ot of several shades of green or it may be black brown or yellow most of the from california from the gulf coast of texas and louisiana and from mexico are black or dark brown most of those from wyoming kansas and oklahoma are green most of if those from the appalachian field are green or yellow all the more productive oil districts of the united states however yield both dark and light oils the color of petroleum as viewed by transmitted light that is as seen in look 1001 I 1 ing ng through a clear glass container contain er full of 01 oil may diff differ er as much as it does wl when viewed by reflected light it is most molt commonly but it may be P some shade of brown yellow or green or rather exceptionally it may be coal black the color of oil is a rough indication of its value oils of the lightest color are ar desirable the generally the most inar 0 pennsylvania oils which have a higher light US ket value than all others are amber oils are rarely aar brown or light green dark and ands such seen in the pennsylvania district comparatively comparativo as are obtained there have a low value charac aba cba g the viscosity of oil is another no fie ids te that differs widely in different at the viscosity is measured by the rate ra which the oil will flow it might be termed ter as its stickiness some thick flow that freely as water others are so and they look and flow almost like stick hang in slimy icicle like points to a atheni into or other object that may be thrust and then with withdrawn drawn specific gravity characteristics oil Is of 0 A third differing characteristic that belie believe ed its commonly weight it is it that all oil will float which means lighter than water yet this is not absolu etly true for some oils are so heavy that they have little or no tendency to come to the surface of water and a few rare oils will actually settle sluggishly to the bottom of a water filled vessel the weight of the oil compared with the weight of an equal volume of clear water at the same temperature ture as the oil is known as its specific gravity and like its color is a fairly reliable indicator of its value the rule is the lighter the oil the higher its value for the light oils contain a larger percentage of gasoline than the heavy oils and just now the gasoline content of crude oil has more to do with determining ter mining its price than any other thing A fourth characteristic of petroleum is its smell most pennsylvania and west virginia oils have what may oe called a kerosene smell california oil has an entirely different smell for it contains compounds known as aromatic hydrocarbons which are not found in the eastern oil the gulf coast oil smells more like the california than the eastern oil but not exactly like either some have an odor that is almost sickening others are almost fragrant where petroleum is found petroleum is contained in the rocks that underlie certain parts of the country most oil is found in beds of sand sandstone or limestone but associated with these beds there are invariably shale improperly called 1 slate by the oil men and clay in practically every producing oil region of the world beds of limestone or sandstone lie between thick beds of shale or clay A region without these rocks has small prospect of containing commercially valuable accumulations of petroleum certain other kinds of rock such as granite gneiss schist and quartzite are distinctly unsuited to form oil fields and filing drilling in such cracks is a pure waste of anoney oney and time of course as there are ex options to all ail rules a few recorded wells have ave struck oil below rocks such as those indicted india seated ted but no paying oil field has yet been opened bened in such rocks in advery fy oil field a little oil is scattered EO 0 generally through the oil bearing beds that at a well reaching these beds at almost any alace ace ls is likely ely to get a showing such as Z rainbow but bt colored film on the drilling water ift il in paying quantities is found only a comparatively small 41 pools in these oil oila practically y every tiny opening in the bearing S bed is filled with oil or with the gas g that tat generally accompanies it th 6 felepe depend formation aon of an oil pool appears to on several conditions though other condition coadis lon s zed that are not yet clearly Y lecog or 01 0 defined ed may account for the absence are s where the e recognized conditions f 0 favorable vo rable ie however in i taen areas of sedi tary indeed rocks by far the most in important and the te 0 only illy edition condition that be de aten eted by v 1 beai can au uc u str facture a study of the surface is the t the he of the rocks by which ameant isy meant way y they ley are folded or tilted where the oil bearing beds are arched or bowed upward the oil has in many places formed pools at the tops of the arches the ideal form for an oil bearing bed or set of beds is dome shaped like a basin or a set of basins turned upside down but in many places simple arching is sufficient |