224 GEOLOGICAL RECONNAISSANCE OF THE DOMINICAN REPUBLIC. 



hilly. Bed rock lies near the surface and crops out at many places along the 

 ravines, though at others it is covered with a mantle of gravel in which 

 pebbles of limestone from the adjacent mountains predominate. The 

 rocks of the slopes of these mountains, which lie about 2 kilometers to the 

 northeast, consist of white limestone containing abundant orbit oidal 

 Foraminifera that are probably of Eocene age. The boundary between 

 the older limestone of the mountain slope and the sandstone and con- 

 glomerate at Higuerito may be a fault. Beds near the contact can be 

 seen plainly along Rio Vfa, where the Miocene conglomerate apparently 

 dips under the older limestone. 



HISTORY OF DEVELOPMENT. 



Of the six wells said to have been drilled before the advent of the present 

 holders of the concession all but one were put down within a few hundred 

 meters of the principal oil seepage. More or less oil is said to have been 

 found in each at depths ranging from 180 to about 290 meters. The 

 deepest well is said to have reached a depth of 400 meters. The earlier 

 wells, which gave the best promise of becoming good producers, yielded 

 oil in quantities that are variously estimated from a dozen up to several 

 hundred barrels a day. Most of the oil was found at depths of less than 

 220 meters, and drilling to greater depths almost invariably resulted in a 

 strong flow of salt water, which was left uncontrolled and destroyed the 

 well. One well was drilled about four kilometers north of Higuerito, 

 in a narrow valley at the base of the mountains. A depth of 200 meters is 

 said to have been reached. The material for the first 125 meters was 

 recorded as "sand and gravel," beneath which was "dark, hard rock with 

 much spar." 



Drilling is now being done on the recommendation of a geologist, who 

 has obtained data that suggest the presence of an elongated dome, which 

 trends nearly north-south and has steeply dipping flanks. The beds to the 

 southeast, along Rio Via, are so greatly crumpled and faulted that a geolo- 

 gist should do much very careful detailed work before he makes recommen- 

 dations for drilling in this region. If the next two or three holes are drilled 

 without obtaining oil it would seem to be advisable to abandon drilling here 

 and to look for another field to the west, where the rocks are less disturbed. 



QUALITY OF OIL. 



The oil from the Azua field is dark brown, very liquid, and of high 

 gravity, the results of various tests showing a gravity of 19° to 21° Baume. 

 It is said to yield no gasoline. The following are the results of tests of a 

 sample taken from well No. 1 at a depth of 960 feet. The tests were 

 made by Leroy M. Law for the Interocean Oil Co. 



