INDICATING DRILLING OPERATIONS 
171 
Distinctive, but mechanically complex, designs are shown in 
figure 2. Any attempt to use these symbols on a large scale 
requires a great amount of labor or reduces the drawing to 
freehand work, which is, as a rule, quite unsatisfactory. 
FLEXIBILITY 
To be of greatest use, a map showing oil and gas development 
must be kept up to date. In order that development which is 
today designated as a location may be changed to an oil or gas 
well or a dry hole when the test is completed and may be indi- 
cated as an abandoned producer at a later time, each symbol 
used must be such that by simple additions it may be changed 
to any other design that might be required in the normal history 
of the well. 
LOGICAL DESIGNS 
Any development map is likely to show a considerable number 
of different features. In reality, however, the information con- 
veyed comes under one of three large heads: producing wells, 
nonproducing wells, and locations. Each of these types re- 
quires a distinct symbol, and inasmuch as a producer is pre- 
dominantly either oil or gas, a distinction must be made between 
these two. The result is that four primary symbols form the 
basis for all designs that may be required. 
Very commonly a well produces both oil and gas. The sym- 
bols for each must be such that they can be combined readily so 
as to produce a single, self-explanatory figure. The addition of 
half the symbol for a gas well to that of an oil well tells clearly 
that the producer is predominantly an oil well but with an appre- 
ciable amount of gas. Or again, the combination of the total 
essentials of the oil and gas symbols should convey the infor- 
mation that the oil and gas are equally divided in the well. 
Nonproducing wells may be dry holes or abandoned producers. 
The reasons for nonproduction may be of great variety, and it 
is often desirable to record these reasons. It is important to 
know, for instance, that oil in quantities too small to be recovered 
