126 BZEQUIEL 0RD0ÑEZ 



the oil from wells where no necks or any other volcanic rock 

 exposure is found in the vicinity. 



The four or five thousand feet thick of uniform shale oil 

 bearing strata is naturally very impervious. We often have 

 to drill hundreds of feet in entirely dry shale even in cióse 

 proximity to the sea and many feet below the ocean level. 



If, as we suppose, the shale formation is not very dis- 

 turbed and there is no real porous continuous strata in the 

 formation, we have to believe, as far our incómplete know- 

 ledge goes to-day, that the porous seams afterwards im- 

 pregnated with oil at the common depths of 2,500 to 2,700 

 feet at which we have generally found the oil, are made by 

 volcanic action. There are to the depths masses of strata 

 corroded by molten lava. It is evident that the strata which 

 becomes porous ought to show a particular physical struct- 

 ure and a somewhat particular chemical composition dif- 

 ferent from the rest of the bedding which facilitates both 

 corrotion and partial absortion by the heated molten lava. 

 We imagine the oil seams elongated horizontally like sills 

 of large dimensions. In order to show the capacities, let 

 us consider aseam or a group of seams capable to produce 

 3.000,000 barréis without interruption, as in the case of 

 the first producing well of México at Cerro de la Pez near 

 El Ébano, or of the famous burned well of Dos Bocas. 



The peculiarities of the strata as supposed to exist, while 

 of a nature absolutely unknown to us, must exist, since 

 there is in our oil bearing strata something like an oil 

 horizon at an average of 2,600 feet. 



The exhaustion of a good producing well is marked by 

 the presen ce of abundant salt water, mud and hydrosul- 

 phuric acid. The porous spaces after giving the oil are 

 probably refilled partially with salt water coming up to 

 the seams by the oil deeper conduits. The ascensión of the 

 oil through the drilling holes is made by high pressure 

 abundant gas; the yielding of the wells is generally in- 



