Engineering Wonders of the World
Volume I

ENGINEERING IN THE WORLD’S OIL FIELDS. 323 Oil Field Geology. sediment. Experts agree that, generally speak- ing, petroleum was formed in the strata in which it is found, though in some cases local conditions have allowed it to find its way through fissures into beds of a more recent epoch. It is doubtful whether petroleum sufficient to repay drilling operations was formed in the rocks in the first instance. But since oil and its gas are, unlike coal and other minerals, able to move in the strata in which they were formed, they have separated from the water contained in the strata, and on account of their lighter weight they have naturally found their way to the highest points in the for- mation. Where the strata have been distorted into what are technically known as “ anticlines ” and “ synclines,” the oil and gas rise into the anticlines. A simple conception of what anticlines and synclines mean is obtained by laying a magazine or thin book on a table and pressing towards each other two opposite edges in such a way as to buckle the pages. The raised folds of the pages accurately represent anticlines, whereas the depressed folds are the synclines. This configuration of the strata must not be confused with sur- face hills and valleys, since these latter gener- ally owe their undulating shape to atmospheric agencies such as rain, frost, and variation of temperature. Practically all the great oil fields of the world are located near the sum- mits of anticlines, though there are important fields in operation where the dip of the strata is hardly appreciable. The productive character of oil fields varies greatly. In some districts there is but one oil-yielding stratum; in others several are profitably exploited. The thickness of the bed may vary between a few and a hundred feet or more. Some beds give up their con- tents readily, owing to the highly porous nature of the bed and to the presence of high- pressure gas ; others are inert, and make it necessary to raise the oil by pumping or baling. In no case is it possible to exhaust the oil beds completely, though it has been established that oil is not being reproduced to an appreciable extent in any of the fields now operated. Certain surface indications usually betray ’ the existence of an oil deposit below ground. These include the escape of inflammable gas, sometimes accompanied by salt water and clayey matter Surface , . , p . , Indications, which forms large mounds, having a central crater, wherein the clay and water is kept bubbling by the issuing gas. In some regions these mud volcanoes attain immense proportions. In Borneo and on the islands off the coasts of Burma violent dis- charges of gas and clay often follow an earth- quake shock, and in several cases,.where the oil beds extend beneath the sea, sufficient material has been ejected to form islands of considerable size, but of short life, as the waves soon wash the material away. Wide areas in the Southern Caucasus ex- hibit many wonderful oil phenomena. Hills may be seen there, down the sides of which flow streams of the semi-fluid clay spued out of the ground by gas. During the great earthquake that totally destroyed the town of Schemakha in 1902, gas issued from the oil beds below, took fire, and increased the general horror of the catastrophe. Historians relate that in olden times so much gas escaped from beneath the sea in the Bay of Baku that boats were actually overturned by the violence of the escape ; and only a few years ago the application of a light on a calm day would kindle the gas over acres of water. The burning of natural gas has long been an object of fire worship in this region. Until recently Parsees used to travel thousands of miles from the East to adore the eternal fires of Surakhany, $acre^ F*res- near Baku, where a temple had been built by the early devotees of this religion. Now,