COMPOSITION AND PROPERTIES OF OIL AND GAS natural gas are among the most important natural resources of the present day. From the crude petroleum refined products are obtained by various processes of distillation, and natural gas is utilized wherever heat and fire may be needed, with excellent results.
Oil and gas are composed of a mixture of hydrogen and car bon, hence known as hydrocarbons. There are also oxygen, nitrogen and sulphur present in various amounts, but merely as impurities.
One speaks of crude oil as having either a paraffin or an asphalt base, depending on the residue remaining after the evaporation of the lighter constituents, which gives rise to several classifica tions to which hydrocarbons so readily lend themselves. In so far as the oil and gas industry is concerned, two classifications are of importance, namely, the paraffin series (oils containing paraffin for a base), and the olefine and naphthene series (oils containing asphalt for a base).
Chemical analysis of hydrocarbons shows that the members forming the paraffin series are composed of hydrogen and carbon in a regular ratio, that is, the number of hydrogen atoms are equal to twice the number of carbon atoms plus two; this relation is represented by the generalized formula The value of such formula; will be apparent when the various members belonging to these series are classified.
The most volatile member of the paraffip series is Methane, or Marsh Gas (CH4); which forms an important part of natural gas, also found in swamp and coal gases. Increasing the propor tion of the composing elements to the next step, we have Ethane (C2H6), which is also a gas, but with different properties than Methane. The differences of the various members have an orderly relation to each other which may be described briefly as follows: Methane, Ethane, Propane and Butane form the gaseous members, the boiling-points of which are increasing in order, which for Methane C. and that of Butane C., and as the boiling-points become higher the liquid and solid members are formed. The specific gravity of the various liquids as well as of the solids increase with the general rising of their boiling points.
The lower members of the paraffin series, which are especially characteristic of Pennsylvania petroleum, are given in the following list: The classification of the olefine and naphthene series is similar to the above, the generalized formula being CnH2n.
Although the systems given above are sufficient for the needs of the oil man, they are not the only ones in use, as there are numerous other regular series, and the generalized formula for some of them is given below: In some fields the crude oil carries both asphalt and paraffin for a base, and such are known as mixed base oils.
Determining the specific gravity of crude oil is the most common test applied by the oil man. In order to simplify the ordinary specific gravity figures (which are obtained by the comparison of the weight of oil with the weight of an equal volume of water under similar conditions), a system known as the Baume scale is in use. On this scale water having a specific gravity of is placed at 10°. The specific gravity of oil is less than that of water, but the figures on the Bantle scale are so arranged that they increase as the specific gravity becomes less, so that the heavier oils will have a lower gravity and the lighter oils a higher one on the Baume scale. It is possible to calcu late the specific gravity from the Baume figure by dividing 140 by the sum of 13o and the Baume degree. This operation may be expressed in the form of a formula Thus, if the Baume gravity of oil is 36° its conversion into specific gravity will be as follows: A hydrometer, equipped with the Baume scale, is in general use in establishing the gravity of the oil. The instrument is The weight of a barrel of oil varies with the change of its gravity, and the relation existing between the gravity and the pounds of oil per barrel is shown by the curve in Fig. 3. A rapid calculation of the weight of a barrel of oil may be made by use of it.
Paraffin base oils generally have a higher gravity than the asphalt base oils, also the color of the oil may give some clue as to its classification, as the paraffin oils are much lighter in color than are the asphalt oils, which are quite dark or black. The color of crude oil ranges from bright yellow to black, depend ing of course upon its composition.
The odor of oil and gas differs in various localities, but the main point of difference noticeable is between the limestone oils and gases and those produced from sandstones. Limestone oil and gas may be recognized from the strong odor of sulphu reted hydrogen, which is not only disagreeable, but may injure or blind the eye if exposed to it for a considerable length of time. Gases from other sources do not act in such a manner.
California and parts of Texas produce asphalt base oils, Illinois a mixed base, and the main'production of the remainder of the oil-producing States are paraffin oils.