118 CLASSIFICATION OF JCHE PUBLIC LANDS. 



Classifications are made by the oil section of the land-classification 

 board. This section consists of three geologists, in addition to the 

 chief of the board. Each .classification is based on data submitted 

 by a field geologist, who is called into consultation at the meeting 

 at which his data are considered. Other geologists having special 

 knowledge of the area under consideration may also be consulted. 

 The factors observed by the field geologist are reviewed in detail, and 

 his inferences and conclusions are subjected to the severest tests of 

 experience and theory. Each factor which can be conceived as having 

 a bearing on the accumulation and present distribution of oil within 

 the area under discussion is carefully considered in all its relations 

 before an attempt at classification is made. 



The record data submitted by the field geologists consist primarily 

 of a map or maps showing the facts observed in the field. On these 

 maps surface contours and drainage are indicated and the details of 

 the areal geology of the region are clearly shown. The position of all 

 petroleum seepages and indications is recorded, as well as the location, 

 by appropriate legend showing the results obtained, of each well 

 drilled within the area examined. All determinations of dip and 

 strike are shown, also the axial lines of all anticlines and synclines, 

 with the direction and amount of pitch of each fold. The location of 

 all land corners found is likewise noted, in order that the classifica- 

 tion may conform to the established system of land surveys. Struc- 

 ture sections are necessary to explain complicated structural condi- 

 tions and indicate the relative thicknesses of the formations and 

 the position of the productive zones. Underground structure con- 

 tours must be drawn to show the relative position of the principal 

 oil-yielding zones above or below sea level, in order that the approxi- 

 mate depth of the oil zone beneath any desired point in the field may 

 be readily determined when the elevation of the point above sea level 

 is known. In a field where considerable development work has been 

 done the preparation of the data should include the plotting of all 

 available well records and the correlation, if possible, of the several 

 oil-yielding zones. 



The principal factors considered by the board in determining the 

 classification of an area are the stratigraphy, the structure, the 

 continuity and character of the oil sands, the quality of the oil, and 

 the presence or absence of water. In many fields the productive 

 sands are confined to a single geologic unit, the formations above and 

 below being uniformly barren. It is therefore necessary to know not 

 only the number and relation of the productive zones in a particular 

 succession of strata but also the geologic system or series and, if 

 possible, the formation or group to which these zones belong. The 

 assignment of productive zones to a definite formation or group out- 

 side of which the strata are known to be barren constitutes an im- 



