Huntley discusses the free escape of gas as one of the causes of the decline of oil fields, the action being somewhat as follows:

(1) Excessive refrigeration due to the free expansion of large quantities of gas forms waxy sediments in the productive stratum and in the tubing of the well. This sediment obstructs the passage of the oil from the sand.

(2) The gas in the immediate vicinity of the well dissipates itself in the initial flow, and the oil production therefore falls off, owing to a lessening of the expulsive force.

The rapid exhaustion of the gas in a certain part of the field may remove the only influence retarding the encroachment of water, which may, by a flanking movement, cut off a large section of the producing area; or water may exist in the lower part of the oil sand, being held in check only by the rock pressure of the gas. If each cubic foot of gas were retained to perform its work of expelling petroleum the pressure would help to retard the water for a considerable period, or until the maximum amount of oil could be recovered. Huntley cites the Hogshooter pool in Oklahoma as an example of a producing gas district that was ruined by having its gas drained too rapidly. Wells were constantly drawn upon to their utmost capacity; hence as no pressure restrained the water under high pressure in the lower part of the productive formation the water flooded one well after another.

FACTORS AFFECTING FLOW OF GAS AND OIL IN DIFFERENT SECTIONS OF THE SAME FIELD OR IN NEIGHBORING WELLS.

The concern of the operator of a plant for making gasoline of natural gas covers all phases of the industry from the occurrence of gas and oil in the well to the final disposal of the gasoline. Hence, in the following pages, is given a brief summary of some of the views that are held regarding the factors that affect the occurrence of gas and oil underground. These views are fully discussed in reports of the United States Geological Survey.

The operator is frequently puzzled to know why wells in one part of a field are more productive than are others in the same field, or why adjoining wells or wells on the same lease, are so erratic as regards output. Another question that may occur to him is why a particular field is productive and an adjoining territory nonproductive. Many observations have shown that the strata yielding oil and gas are practically identical, the gas usually accumulating in the domes of the arches in the strata or in other elevated parts of the deposits. Gas almost invariably accompanies oil where conditions favor its accumulation, but oil is frequently found almost unaccom

a Huntley, L. G., Possible causes of the decline of oil wells and suggested methods of prolonging yield; Technical Paper 51, Bureau of Mines, 1913, pp. 6-7.

Huntley, L. G., op. cit., p. 7.

panied by gas on account of the collection of the gas in the highest portions of the strata or because of its escape through imperfections of the covering layers. Brine almost universally accompanies the oil

and gas.

In addition to possessing a porous structure for holding the oil or gaseous contents, the reservoir rock must be entirely covered with an impervious layer, the commonest and most perfect cover being a fine-grained shale, whose imperviousness and freedom from fracture enables the "sand" to retain the gas or oil. Gas, oil, and water are frequently found distributed according to their specific gravities, gas disengaging itself from the fluid and rising to the highest point in the beds, and water displacing the oil and finding a resting place as low down as possible. When oil and gas strata are comparatively little undisturbed, each well usually draws its supplies from a considerable area; indeed, the owners of wells in the United States are usually compelled to continue to raise oil, without regard to the conditions of market, to prevent its being obtained by neighboring leaseholders. On the other hand, faults and dislocations of strata may limit the area over which a single well draws its supplies, and so impede the free passage of the fluid that the pressure is small. It is now generally admitted that the pressures in wells are entirely due to accumulations of gaseous hydrocarbons, chiefly methane, which were formed with the liquid hydrocarbons and exist in a highly compressed condition and dissolved in the petroleum or accumulated in the beds immediately overlying the oil stratum. Where the gas has been allowed to escape freely, petroleum rarely flows from a well, and never, perhaps, unless left for a long time, rises to the surface unaided.

Discrepancy in production may in some cases be attributed to local variations of the reservoir rock, but Arnold and Garfias a state that an abnormally low production of oil can be traced to one or more of the following causes: Inefficient management; improperly finished well; poor condition of casing; failure to perforate casing, or inadequate size and number of perforations; obstruction of the bore-hole by tools or fragments of débris; failure to exclude water, which sometimes results in the inrush of sand; effect of neighboring wells; and drawing on a secondary sand only. Some of these causes affect the yield of gas also. Arnold and Garfias add that although at some wells conditions can not be remedied, and at others the expense incurred would not be compensated by the added production, nevertheless, in most instances, an intelligent study of the trouble and its sources will disclose some comparatively simple means of improving conditions so as to increase the total yield.

b

a Arnold, Ralph, and Garfias, V. R., Methods of oil recovery in California: Technical Paper 70, Bureau of Mines, 1914, p. 9.

Arnold, Ralph, and Garfias, V. R., idem.

EFFECT OF DRILLING NEIGHBORING WELLS.

Regarding underground connection between neighboring wells Huntley has the following to say:

The first well drilled in a group will tend to set up drainage channels and divert large quantities of oil from a considerable area. Subsequent wells come in as much smaller producers than the original well. Again, in loose unconsolidated sands, such as are found in the Caddo field in Louisiana, and in the famous Glenn pool, in Oklahoma, if a well stops pumping for a day, the surrounding wells extend their own channels, breaking down the drainage systems of the first well, to the extent that it is often difficult to again recover oil from the well that has stopped pumping. As a result the wells in the Glenn pool are pumped 24 hours a day, 365 days in a year. The condition of the sand in the Glenn pool was brought about somewhat artificially by the use of enormous quantities of nitroglycerin in shooting. The sand, originally coarse and porous, has probably been shattered throughout the entire producing

area.

In certain lenticular formations, described by the oil man as "spotty," of two wells drilled only 150 feet apart, one has been a large producer and the other a dry hole. This discrepancy may be due to drainage conditions or may be caused by an intervening hard spot in the oil sand. If it is caused by drainage conditions, the stopping of the producing well would probably cause the other to produce. Again, wells 1,000 to 2,000 feet apart are in places so closely connected underground that the muddy water used in drilling one well has been pumped out by another well a considerable distance away, not necessarily the well nearest to the one being drilled.

Huntley further states that in a tight sand neighboring wells do not affect each other to the same degree as in a very porous stratum; that is, such pronounced drainage channels toward the wells first drilled are not formed.

EFFECT OF FORMATION OF WAXY SEDIMENT.

Most of the plants for making gasoline from natural gas draw the gas from old wells, many of which are very small producers of oil. Hence many of them have not received much attention as regards upkeep. One result of this inattention is the formation of waxy sediment or paraffin. Regarding the formation of this waxy sediment Huntley comments as follows:

с

Petroleum in the so-called paraffin-oil fuels consists of hydrocarbons of the paraffin series, which range from the heaviest oil to the lightest gas. The gaseous constituents of petroleum exist in what may be likened to solution, much like the gas of soda water, and as such expand and escape when the pressure is relieved by a well. The sudden expansion and volatilization of such light hydrocarbons has a refrigerating effect, like the expansion of ammonia gas in an ice machine, chilling the remainder of the liquid petroleum and causing the separation of the heaviest paraffin as a waxy sediment. * * This, * * along with water and fine rock sediments, clogs the pores of the sand and obstructs the passage of the oil into the well.

a Huntley, L. G., Possible causes of the decline of oil wells and suggested methods of prolonging yield Technical Paper 51, Bureau of Mines, 1913, pp. 23–24.

Huntley, L. G., op. cit., p. 22.

e Huntley, L. G., op. cit., p. 6.

HISTORY OF THE MAKING OF GASOLINE FROM NATURAL GAS.

That gasoline can be extracted from natural gas has long been known, ever since oil and gas have been noticed in some gas pipe lines, but the production of gasoline from natural gas has only within the past few years become of commercial consequence, owing principally to the ever-increasing demand for gasoline.

TWO SUCCESSFUL PLANTS IN 1904.

A. Fasenmeyer made gasoline from the gas of oil wells near Titusville, Pa., in the fall of 1904. His plant is almost within sight of the old Drake well. His first equipment was crude. The gas from the wells after passing through the gas pumps was cooled by means of a coil of pipe placed in a tank of water. The condensate produced was allowed to drip into a wooden barrel. The losses resulting from evaporation were large. The product when first collected had a gravity of 80° to 90° on the Baumé scale. His production the first year was approximately 4,000 gallons, for which he received 10 cents per gallon. Tompsett Bros., of Tidioute, Pa., claim to have preceded Fasenmeyer in the making of a commercial venture out of the process. They are operating successfully at the present time.

As these ventures proved a commercial success attention was turned to the designing of better plant equipment. Gas and oil operators in other oil fields in the United States proceeded to install gasoline plants.

EARLY METHODS.

At first common gas pumps, with pressures not exceeding 50 pounds per square inch, were used. Condensation was effected by running a pipe through the earth to the gasoline receivers. Mr. William Richards, of Warren, Pa., claims to have been the first to install high-pressure compressors. His first experiments, made in 1905, were with pressures of 400 pounds per square inch. Later he came to the conclusion that a pressure of 250 pounds per square inch was sufficient to make gasoline that was about right for shipping. Mr. Richards's plant was located at Mayburg, Pa.

In the first plants for making gasoline from natural gas the cooling system consisted in general of a series of pipes. In some plants the pipes were cooled by the air, but in most plants were immersed in tanks containing water or else the water was allowed to drip over the pipes. At most plants the collecting tanks were open to the atmosphere. The residual or waste gases were allowed to escape. After the condensate had "weathered"-that is, when the lighter fractions had been allowed to volatilize and escape into the atmosphere-the product was marketed.

LATER IMPROVEMENTS.

The next step in the industry was to pass the gases from collecting tanks from the single-stage compressor through a higher-stage compressor. The gases were again cooled. In this manner a second and more volatile product was obtained, which was mixed with the product from the first-stage compressor. This mixture was again "weathered" and then marketed. F. P. Peterson, while connected with a gas-engine company in Grove City, Pa., claims to be the first to use the two-stage compressor method. As producers realized the great waste involved in this process, another improvement was introduced, as follows:

The condensate produced from both stages of compression and cooling, which had a gravity of 80° to 100° B., was mixed with refinery napthas until the specific gravity had been lowered to 60° to 76° B. By this means there was obtained a product that evaporated more slowly than did the condensate. The process of blending is more fully discussed elsewhere in this report.

The waste gases, after the gasoline had been extracted, were in part used for plant operation, and, in some plants, the remainder was returned to gas mains which supplied towns with gas for lighting and manufacturing purposes. In most plants the waste gases were allowed to escape into the atmosphere. At present much information is at hand as the result of the experimental work done, so that plants are now installed to meet particular requirements. The advisability of employing single or double stage compressors, the pressures to be used, the method of handling and disposing of the condensate, and the disposition of the waste gases are all considered.

PATENTS ISSUED.

Chute a gives the various patents that have been taken out covering the condensation of the hydrocarbons in natural gas, as follows:

In 1866 Johnson received patent No. 54910 which clearly discloses the art of rendering liquid the vapors that rise with or are forced up with petroleum.

In the Heinzerling patent of 1897, No. 575714, which expired January 28, 1914, there is shown an air-compressor or gas-compressor cylinder and a gas-expansion cylinder, both coupled to a flywheel, with a series of condensers and heat exchangers between. The specification clearly explains that the gas is to be compressed in the first cylinder and cooled in two condensers in series, with condensation of the condensible liquids, which are removed by appropriate valved containers depending from and connected with the condensers. Thence the water-cooled gas passes to other condensers

a Chute, H. O., The patent processes for making casing-head gasoline: Jour. Met. and Chem. Eng., 12, No. 3, March, 1914, pp. 147 and 148.

vol.