viii. a. 5 Pratt and Smith: Petroleum Resources 371 



the surface here appear to be about 1,400 meters, stratigraphi- 

 cally, below the base of the Canguinsa sandstone, and the dip is 

 about 35°. The eastern limb just across the axis in the upper 

 valley of Vigo River is equally desirable as a drilling site except 

 for the steeper dip (from 60° to 70°) of the strata. 



If oil is obtained in any of these localities, a number of places 

 which have not been mentioned may become desirable territory, 

 depending on what horizon the oil is encountered in and on other 

 conditions which will be revealed by the drilling. More detailed 

 work in the vicinities of A jus and Sili may show that there are 

 favorable drilling sites at these places, and as has been suggested 

 the neighborhood of the volcanic agglomerate may prove valuable 

 as drilling territory. 



It will be apparent that companies entering this field should 

 be prepared to drill several wells in order to prospect any local- 

 ity thoroughly. The failure of a single drilling should not be 

 accepted as establishing the absence of exploitable petroleum 

 resources in any particular zone or in any one anticline, and 

 certainly should not condemn the whole field. The drilling of 

 unsuccessful wells is common in producing fields, where the geo- 

 logy is well known and the experience gained from many com- 

 pleted wells is available. It would be surprising, indeed, if the 

 early drilling on Bondoc Peninsula did not result in a large pro- 

 portion of "dry" wells, even if exploration were ultimately 

 successful. 



Skilled and experienced drillers should be secured. It is an- 

 ticipated that drilling on Bondoc Peninsula will be rendered 

 difficult by the unconsolidated, caving nature of the shale series, 

 and, possibly, by the necessity of sealing off water-bearing sands. 

 Because of the fact that these difficulties have been overcome 

 successfully in the California oil fields, drillers from these fields 

 should have experience that would be particularly valuable in the 

 local field. 



The exact location of wells should be preceded by further and 

 more detailed geologic study of the region to be tested. The 

 relation of possible sites to the known and suspected petroliferous 

 zones should be carefully determined, and local variations or 

 irregularities in the general structural and geologic features, as 

 outlined in this report, should be noted before a decision is 

 reached as to the best drilling site. The progress of the first 

 drilling likewise should receive particularly close attention from 

 a geological standpoint since it may reveal conditions not manifest 

 at the surface which would alter the course of exploratory work. 



