These folds are usually not strongly marked, and in fact are often inconspicuous. In many, perhaps most, cases the folds are in fact nothing but terraces, or "arrested anticlines." That is to say, the rocks in certain localities, instead of having the normal dip to the west, lie nearly level. In comparatively few places throughout the greater part of the field, may wellmarked easterly dips be observed.

Careful studies of geological conditions have demonstrated that there is in the Mid-Continent field a rather definite relation between the structure of the rocks and the occurrence of oil and gas. Those who are considered to be the best authorities on the subject do not hesitate to say that, so far as observation goes, practically every oil pool in the Mid-Continent field may be accounted for by structure. It must be admitted, however, that it is not always possible to determine this structure from surface observation, so that a careful study of well records is often necessary to determine it; but, when once understood, the relationships between structure and production are usually obvious.

In the southern part of the area occupied by Pennsylvanian rocks, that is to say, in the region from Muskogee southwest to Atoka, and southeast to Forth Smith, Arkansas, the general westerly dips noticed farther north give way to a series of alternating anticlines and synclines.

There has been no great amount of drilling in this region, and very little petroleum has so far been found therein. It is, however, a very significant fact that, throughout this region, in practically every known case where drilling has been done along anticlinal folds, natural gas has been found. The gas fields near Fort Smith and Manfield, Arkansas, and near Poteau, Spiro, Kinta, Red Oak and Wardville, Oklahoma, are located on or near the axes of well-marked anticlines. Up to the present time not enough drilling has been accomplished, throughout this part of the Mid-Continent field, to demonstrate the absence or presence of oil in quantity. It is altogether probable, however, that extensive operations will reveal the presence of considerable amounts of petroleum.

Relation between Sands and Structure.

Within the developed portion of the Mid-Continent field where, as stated above, the anticlines are not so conspicuous as in the regions just discussed, the largest oil pools almost invariably occur where an unusually thick sand underlies an anticlinal fold, or a terrace. The Bartlesville, Glenn, Cleveland, Cushing, and in fact all the larger pools that have produced unusually large amounts of petroleum, contain this very favorable combination of thick sand and structure. In many instances, however, oil has been found in considerable quantities in regions where there is little or no evidence that the normal western dip of the rocks has been interrupted. Under such conditions, however, the drill reveals the fact that the oil sands are unusually thick. Instances of this kind occur in certain parts of the Bartlesville pool, in the Bird Creek pool, in the Shallow field, and in many of the pools in the Osage Nation

PRODUCTION AND DEVELOPMENT.

The production of petroleum in the Mid-Continent field increased from 74,714 barrels in 1900 to 59,343,850 barrels in 1911.

During the past year there has been more development than ever before in the history of the field. This may be accounted for by the steady advance in the price of petroleum. In 1908 the petroleum in the Mid-Continent field sold for 35 cents per barrel. At the time of this writing, May 1913, the price is 88 cents per barrel, and it will probably increase.

Within the past few months there has been much prospecting in all parts of the Mid-Continent field. The Cushing pool, which bids fair to rival the world-famous Glenn pool, was first opened in March, 1912. Its daily production is now 100,000 barrels. Within the year the known areas of a number of the older pools have been materially extended and a number of new pools have come to light.

A region occupying some five counties in southwestern Oklahoma, which has heretofore remained unexploited, is now attracting much attention. Within the past year a number of wells have been drilled throughout this region, and practically all have produced oil or gas. Geologists who have studied conditions in this part of the state are of the opinion that this field, when developed, may rival the field already developed in the northeastern part of the state.

NATURAL GAS.

The amount of natural gas produced in the Mid-Continent field is very great. At least 90 per cent. of all the oil wells so far drilled contain natural gas. In many cases the wells produce gas only; however, gas and oil usually occur in the same sand. In many cases after the gas in a well has been practically exhausted, oil is produced. To use the drillers parlance, "the well drills itself into oil."

The capacity of gas wells of the Mid-Continent field varies up to 50,000,000 cubic feet per day. Some of the most extensive gas fields so far discovered lie near Iola, Independence and Caney, Kansas, and Copan, Bartlesville and Collinsville, Oklahoma.

A well recently drilled to a depth of less than 700 feet in the new field near Loco, Stephens county, southwestern Oklahoma, is producing 25,000,000 cubic feet of gas per day.

The gas from the Mid-Continent field is utilized both for manufacturing purposes and for domestic use. Gas from this field, supplied the greater part of the cities of Oklahoma and eastern Kansas, and has been piped as far as Joplin, Kansas City and St. Joseph, Missouri. Much of the so-called casing-head gas is now being utilized for the manufacture of gasoline or petrol, there being about twenty-five gasoline plants in operation in the field.

The waste of natural gas in this field has been enormous. Legislation has checked, but has by no means stopped this gigantic waste. At the present time tens of millions of cubic feet of the most valuable fuel is being dis

sipated into the air each day. Yet for this negligence there seems to be no immediate, effective remedy.

At present there is no way of estimating the amount of natural gas now available in the Mid-Continent field, but it is probably between one billion and two billion cubic feet per day.

FUTURE OF MID-CONTINENT FIELD.

There is no means of knowing accurately the possible extent of the Mid-Continent field, but, taking into account all the available data, including the stratigraphy and structure of the rocks, and the known occurrence of oil and gas under existing conditions, it may safely be estimated that, at the present time, not over one fourth of the future available territory in Oklahoma and Kansas has been drilled. New fields are constantly coming to light and the limits of old ones are being extended.

Many of the wells now in operation have been producing oil for fifteen years, and are by no means exhausted. At the present rate of development, it will be many years before the productive area of the fields has been determined. It will be many more years before it all will be drilled. There need be no surprise if the Mid-Continent field is producing both oil and gas one hundred years from this date.

NATURAL GAS IN TRANSYLVANIA.

BY

JULES DE SZÁDECZKY,

Professor, Royal Francis-Joseph University, Kolozsvar, Hungary.

In connection with the discussion of the Coal Resources of the World, the recent discovery in Hungary of important quantities of natural gas may prove to be of interest.

Burning gas has long been known in the upper Miocene of Transylvania. JACQUIN in 1808, and later PARTSCH in 1827, gave detailed descriptions of the "burning well" of F. Bajom and Magyar Sáros between the two Küküllö rivers."

1

It is only the deep boring of recent years, conducted by the Finance Department of Hungary, that has given a proper conception of the great richness in natural gas of Transylvania. It must indeed be mentioned that these deep borings were first made not for gas but for the purpose of finding kali-salts, which some Hungarian geologists believe to be associated with the rich, late Tertiary (Miocene) salt deposits.

The first deep boring to discover kali-salts was made in the centre of the Tertiary basin of Transylvania in Great-Sármás in 1908. It was discontinued at a depth of 627 metres because of technical difficulties. The little methane mingled with salty water which spouted out of the marly sandstone at a depth of 460-470 metres, and later at 570-580 metres, was given little attention.

As this boring was made in the synclinal portion of the folded Miocene strata, the next boring was made 2.9 kilometres farther toward the northeast in the anticlinal, where it encountered at 22 metres natural gas and iodine-bearing salt water in sandy strata. At 302 metres drilling was stopped by a tremendous flow of natural gas, flowing at the rate of 193 cubic metres per second, that is, 912,124 cubic metres in 24 hours. The temperature of the gas is 4°C.

Later geological investigations, designed by the government to supply detailed information regarding the Tertiary basin, showed that the vault-like anticline of sandy Miocene strata contains natural gas chiefly.2

1 Geologie Siebenbürgens, von Fr. Ritter von HAUER und Dr. G. STACHE, Wien, 1863, S. 592, etc.

2 The results of these studies were published in 1911 in a book, entitled: I. Az Erdélyi Medence földgázt tartalmazó ántiklinálisairól, by Prof. DR. BÖCKн HÚGÓ. II. A Nagysármás és Kissármás községek határában végzett mélyfúrások leirása, by Ing. BÖнм FERENC. and will be republished this year (1913).

The anticlinal axes do not run straight but curve in zig-zag courses that seem to be influenced by the older marginal rocks of the basin.

The gas-bearing strata are curved not only horizontally, but as can best be verified by the interstratified dacitic tuff beds-exhibit great vertical undulations. In this manner are formed the great gas-bearing vaults that have been mentioned above.

The first boring showed also that strata which lie nearly horizontal at the surface have greater inclinations in depth, for instance, 40° at 490 metres. This condition obtains frequently in the later Miocene beds of Transylvania, as well as in the petroleum fields of Roumania, where it was first observed by Prof. MRAZEK and named "diapir fold."

The detailed geological investigations showed also that, on the margin of the Miocene basin the anticlinal folds are much closer together and have much greater inclinations on the surface than towards the middle of the basin, where they are farther apart.

The richest gas-bearing folds have only a slight dip at the surface but become more steeply inclined with depth, as is the case in the district of Sármás.

At the present time ten wells have been bored to study the gas-bearing Sármás dome, which give more than 1.5 million (1,658,434) cubic metres of natural gas per day. These wells show that not only is the country near the anticlinal axis rich in natural gas but also that which lies within one kilometre of the axis.

All the wells are capped and ready for the utilization of the gas.

In connection with the gas field of Sármás must be mentioned the great gas eruption of October 29th, 1911. This occurred near the second well, in a place where previously, within the memory of man, gas mingled with salt water burst out along a line of fracture and was utilized for the treatment of rheumatic diseases, constituting a primitive watering-place. This gas eruption was preceded by slight earthquakes, and when the gas caught fire it burned with high and terrifying flames during the first night, gradually subsiding during the following days, until it was finally extinguished by the militia.

This gas eruption seriously damaged the railway near by and destroyed the simple watering-place. It was also of great interest to geologists, for during our last investigations we found traces of many hundreds of such eruptions, which produced mud volcanoes generally similar to those of the last eruption at Sármás.

On the anticlinal axis of Sármás a second dome forms the gas field of Mezö Sámsond, which is now tapped by two wells 365.7 metres and 215.40 metres deep respectively, and giving 83,000 cubic metres and 30,000 cubic metres of gas per day respectively or, together, 113,000 cubic metres. The dome of Mezö Sámsond, as I have proved by tracing the course of one thin dacitic tuff bed, is more compressed than that of Sármás.

The third great dome on this anticlinal line is that of Mezö Kapus, which has not yet been examined by deep borings.