372 The Philippine Journal of Science 1913 



CONCLUSIONS 



The existence of petroleum on Bondoc Peninsula is established 

 by the presence of seeps of petroleum associated with inflammable 

 gas at various places throughout the oil field. 



All the petroleum encountered so far is similar in character 

 and of a good quality. It is of low specific gravity, and contains 

 a large proportion of light oils which would make it of relatively 

 high value as a commercial petroleum. 



The seeps are in highly inclined strata which are probably in 

 all cases part of the structure of anticlinal folds. From this 

 association it is believed that the petroleum in this field has tended 

 to collect in the crests of anticlines in accordance with the gen- 

 eral law of petroleum accumulation. 



The petroleum occurs associated with certain horizons in an 

 extensive series of beds of sandstone and shale (Vigo shale), 

 which is similar in character to the oil-bearing rocks of productive 

 fields. The principal seeps are found in the upper part of this 

 series in a zone designated as the Bacau stage, which is predom- 

 inantly shale, but contains subordinate beds of sandstone. In 

 its seepage, the petroleum is associated with the shale rather 

 than the sandstone and may be observed in some cases to come 

 directly from the shale, but this association may be due to the 

 ready escape of the light oil from the outcrops of the coarse- 

 grained beds and its retention at the surface in the fine-grained 

 shale only. 



The petroleum may have originated, in part at least, in the 

 globigerina and other organic remains found in the strata with 

 which the oil is associated. There is a possibility, however, that 

 the oil is not indigenous to the strata in which it now occurs, but 

 has migrated from its source in another horizon. Beds which 

 are concealed so that they cannot be examined at the surface and 

 which, consequently, may be sources of oil occur as follows: (1) 

 Members of the Vigo shale above the Bacau stage, concealed by 

 the overlap of the Canguinsa sandstone which overlies the Vigo 

 shale unconformably ; (2) the basal portion of the Vigo shale 

 which has not been uncovered by erosion; and (3) any sedimen- 

 tary formations which may underlie the Vigo shale. 



The structure of Bondoc Peninsula includes a number of anti- 

 clinal folds, and the conditions along some of these anticlines 

 are considered favorable for the accumulation and retention of 

 the petroleum, whether it occurs in all or in any one of the hori- 

 zons at which it is suspected. 



