462 Subsurface Geologic Methods 



Thomas A. Banning, Jr., of Chicago, Illinois. Under the title "Measuring 

 and Recording Various Well Drilling Operations" Mr. Banning has filed 

 application for Letters Patent in the United States Patent Ofl&ce. This 

 application reviews thoroughly the history of the art of drilling-time re- 

 cording and investigates means by which data measurable during the 

 drilling of a well can be recorded and plotted to produce logs such as are 

 described in this article. Field tests are on record in which remarkable 

 accuracy in depth measuring and time coordination were achieved. Such 

 equipment, when available, will increase the application of drilling-time 

 data as here discussed, and undoubtedly will open up new channels of 

 research into lithologic properties hitherto inadequately understood. 



Application of Drilling-Time Logs 



Many of the uses for drilling-time logs have been cited and illus- 

 trated in the literature. The value to drillers, contractors, and operators 

 is well known. The chief concern is the drilling of the greatest amount of 

 hole in the shortest time possible consistent with good safety practices. 

 At the same time anyone connected with the drilling of an oil well knows 

 that the purpose of drilling a hole is to gain information, the use of which 

 may lead to production of oil or gas. The contractor may find drilling- 

 time records most useful in the analysis of operations and the study of 

 down time as well as pay time. The performance of different types of bits 

 in various formations can be observed directly on drilling-time charts 

 which reflect the types of formations being penetrated. The driller finds 

 drilling-time charts of value as a record of his tour showing exactly how 

 much he drilled, what type of formations were encountered and their 

 depths, and a record of time down for sundry purposes. The guess work 

 is eliminated. But the driller, like the operator, is concerned with finding 

 oil, and he knows that reservoir beds are porous media overlain by hard or 

 impervious layers. If he knows he is drilling in a section where potentially 

 productive formations may occur and has not been given precise instruc- 

 tions in respect to coring, logging, or testing, the driller uses his best 

 judgment in the interest of the operator. When he observes a drilling- 

 time break, he may stop drilling and circulate samples for examination and 

 wait for orders before drilling past any formation that might carry oil 

 or gas. The drilling-time charts provide an indisputable record of where 

 the top of the break was encountered and how many feet have been drilled 

 in it. 



The geologic importance of drilling-time logs is evident primarily 

 in the fact that foot-by-foot information is available for correlation. As 

 has been shown in figures 215 and 216, a drilling-time log, plotted on 

 a time scale such that the amplitude between fast and slow peaks gen- 

 erally corresponds to the range between the shale base line and the maxi- 

 mum peak of an electric-potential curve, provides the geologist with data 

 that may be used, within reasonable limits, for much the same purposes 



