288 REPORTS ON THE STATE OF SCIENCE, ETC. 



6. The lack of a satisfactory relation between geothermal conditions and 

 structure in this field may be attributed to the following three factors : 



(a) The variation of the gradients within the narrow limits of only 

 a few feet per degree of temperature ; 



(b) The unusual conditions of development and production in- 

 volving the very close spacing of wells and the flow of large 

 quantities of gas and oil under high pressure ; and 



(c) Natural conditions of ground-water circulation causing the 

 establishment of abnormal shallow temperatures. 



Long Beach field. — Nineteen wells were measured in this field, making 

 a total of forty-three completed. The total variation of depth to a ioo° 

 isothermal surface is about 200 ft. and of reciprocal gradients about 8 ft. 

 per degree. The mean isothermal depth is 1,534 ft- and the mean reciprocal 

 gradient about 53 ft. per degree Fahrenheit. 



Temperature Gradient in the Pechelbronn Oil-bearing Region, Lower 

 Alsace : its Determination and Relation to Oil Reserves. 



By I. O. Haas and C. R. Hoffmann. 



Bulletin of the American Association of Petroleum Geologists, vol. 13, no. 10, 

 October, 1929, pp. 1257-1275. 



The authors summarise their experience in making temperature measure- 

 ments in oil wells and consider whether it is possible to ascertain the 

 existence of petroleum on the basis of a smaller or a larger temperature 

 gradient. 



The article is divided into the following paragraphs : 



1. Description and discussion of thermometers used. 



2. Possible sources of error in temperature measurements. 



3. Carrying out of temperature measurements. 



4. Calculation of temperature gradient. 



5. Criticism of results obtained. 



6. Application of results obtained. 



7. Attempt at an explanation of temperature variations. In the abstract 

 of the article given by the authors they say : 



' Numerous temperature measurements have been made during the 

 last 10 years in the Pechelbronn oil-bearing region, to aid in the search for 

 petroleum deposits. 



' However, the results of the study of approximately 500 measurements 

 clearly show that the isogeotherms are influenced primarily by the 

 tectonic structure of the Rhine Valley graben. They show a nearly 

 regular rise from the edges to the central part of the graben ; also not 

 uncommonly they approach one another. Such increase of temperature is 

 especially marked in the fault zones. 



' Seemingly the isotherms are not influenced by larger or smaller oil 

 accumulations ; therefore, the presence of oil cannot be looked upon as 

 the cause of the relatively elevated temperature. 



' It is perhaps possible to explain the rise of temperature toward the 

 central part of the graben by a gradual change in the nature of the deposits. 

 Coarse-grained sandy beds of the graben edges are gradually replaced 

 toward the centre by increasingly finer sands, and finally by finely 

 laminated marls. It is possible that these finest deposits act as a sort of 



