1158 EXPLORATION GEOPHYSICS 



library, and the court opinions in these cases, if collected, would make a 

 legal encyclopedia. 



Relatively few patent cases reach the United States Supreme Court, 

 because ordinarily that court is accessible only when there are conflicting 

 decisions in two judicial circuits on the same patent. Occasionally the 

 Supreme Court will accept for consideration a case outside the general 

 rule, where special public interest appears, or when members of the high 

 court believe that the federal courts subject to their policy-fixing powers 

 (in the form of interpretation of the law) have strayed from home. 



Announcement of a Supreme Court decision in a patent case is always 

 news in the patent world, and sometimes contains elements of surprise. 

 The petroleum industry may claim the distinction of recently contributing 

 such a case to the annals of American jurisprudence. This case is entitled 

 "Halliburton Oil Well Cementing Company vs. Walker, et al.," and is 

 reported at 329 U.S. 1, as well as at 71 U.S.P.Q. 175, and in some other 

 publications. The patents in question were granted to Cranford P. Walker, 

 who lost the broader claims after several years' litigation and seven different 

 court rulings. 



This case is a good primer in patent law to a point, and its facts well 

 illustrate certain patent problems of the petroleum industry. 



The patent involved (No. 2,156,519, granted May 2, 1939, and entitled "Means for 

 Measuring the Location of Obstructions in Wells") covered a method for the measure- 

 ment of the distance from the casing head to the fluid surface, and was one of several 

 patents which Walker secured in this field. 



The measurement of distance by timing the travel of a sound from its point of 

 inception to an obstruction and its returning echo had long been known. In 1898, a 

 patent was granted describing an apparatus whereby the noise from a gun might be 

 injected into a tube; the returning echoes from obstructions vibrated a diaphragm, 

 which moved a stylus to record a graph on paper. (See p. 1126.) Recognizing the need 

 for measuring the distance to the fluid surface in deep oil wells, where it is 'impractical 

 to measure depth by the old method of lowering a rope or cable, the oil industry in the 

 1920's began to look to the sound-echo time method as a possibility. Work was initiated 

 by a number of investigators. Lehr and Wyatt secured a patent on measuring the 

 distance by timing the echo of an "impulse wave" generated by a "sudden change in 

 pressure". The Lehr and Wyatt apparatus comprised a gas cylinder with a quick- 

 opening valve by means of which a short blast of gas could be injected into a well. 

 It was particularly noted that the wave impulses could be recorded by use of a micro- 

 phone which might include an amplifier and a device to record a picture of the wave 

 impulses. Thus Lehr and Wyatt contrived an apparatus composed of old and well- 

 known elements or parts in combination to measure and record the time required 

 for a pressure wave to travel down and back from the fluid surface in an oil well. 



Under certain conditions the Lehr and Wyatt apparatus and method were found 

 to be inadequate for the reason that pressure waves do not always travel at a constant 

 velocity. Consequently the mere measurement of the time elapsing between the initia- 

 tion of the wave and the return of the echo may not allow accurate calculation of depth. 



Cranford P. Walker and other early workers were acquainted with the work of 

 Lehr and Wyatt, and soon active research work was in progress to devise a method 

 which would be more accurate in results. It was well known in the art that the tubing 

 string is made up of pipe sections coupled together; where the coupling joints occur. 



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