Subsurface Methods as Applied in Geophysics 1107 



was necessary to contour phantom horizons. Figure 584 is a combined 

 seismic and subsurface cross section, which compares the phantom horizon 

 with well data. This seismic program discovered the Odem and East 

 Riverside oil fields and the Riverside and O'Neil gas fields.®^ 



La Gloria Area, Jim Wells and Brooks Counties, Texas — Favorable 

 torsion-balance results in the La Gloria area of Texas initiated a correla- 

 tion seismograph survey in 1936. Two years later the area was again shot; 

 this time the continuous dip-profiling technique was used. The dips in- 

 dicated by the reflections were plotted on cross sections, a phantom hor- 



Figure 585. Reflection-seismic-dip cross section across La Gloria field, Texas. Phantom 

 horizon shown by dotted line. (After Wooley. Reproduced permission Geophysics.) 



izon was drawn on each section, and the traverses were closed and adjusted. 

 Figure 585 is a typical dip section across the La Gloria field. A contour 

 map prepared on the basis of dip data showed about 250 feet of closure. 

 (See fig. 586.) After the completion of the dip survey, a continuous cor- 

 relation survey was made over the closed structure for comparison with the 

 dip map. The results of this survey agreed closely with the dip map, as 

 may be seen in the figure. The discovery well was located from these 

 maps and now produces from sands in the Frio formation of Oligocene 

 age.^^ 



Tucupita Oil Field, Venezuela — The Tucupita field is located in 

 eastern Venezuela and was discovered on seismograph work done during 

 the years 1939 to 1941. Continuous spreads were used with jump correla- 

 tions being made across gaps caused by faulting and zones of no reflec- 

 tions. Good correlation was obtained, even though the section contained 



'- McCarver, H., and West, L. (k, The Geology and Geophysics of the Odem Oil Field, San Patricio 



County, Texas: Geophysics, vol. 12, no. 1, pp. 13-29, Jan. 1947. 

 S3 Wooley, W. C, op. cit. 



