suggested that this part of the section might be reef facies over the crest of the 

 structure. Figure 41-19 is a west-east seismic cross section of the Cuervo pros- 

 pect, and Figure 41-20 is a geologic cross section of the same profile. Gravity 

 data (fig. 41-21) indicated a gravity maximum anolmaly, and the photogeologists 

 outlined a strong positive drainage anomaly coincident with the core-drill high. 

 Amprex's landmen were able to lease this prospect completely (fig. 41-7), and 

 title work of the leases covering the prospect indicated that all of the land- 

 owners had clear titles to their land. Civil engineers had surveyed the area and 

 established physical and ownership boundaries on the ground. 



Amprex's staff now filed with civil and national authorities requests for 

 permission to drill a wildcat test in the search for oil and gas at a described 

 location, agreeing to conform to the laws and regulations governing such opera- 

 tions. 



Following the approval of this request to drill, Amprex's Production De- 

 partment assigned from its staff petroleum engineers, drilling superintendents, 

 mud engineers, and tool pushers to conduct the operations required in the 

 drilling of this wildcat test. A rig was contracted from one of the larger drilling 

 companies of the western area and trucked into the location after the civil 

 engineers had constructed an all-weather road into the location. 



From information obtained from the drilling of the No. 1-C stratigraphic 

 test, Amprex's production group, which was in charge of the drilling operations, 

 planned, with the assistance of the geologists, casing, coring, and logging pro- 

 grams to be coordinated with the instructions of the well geologist and paleontol- 

 ogist while the well was being drilled. The geologist on the well would instruct 

 the production group where to core, test, and log; and, if possible and practical, 

 the production group would execute these requests. 



The drilling of a wildcat well is perhaps one of the most well-organized 

 operations that an oil company conducts. Inasmuch as this is usually the end 

 result of an expenditure of thousands of hours of exploration and frequently of 

 millions of dollars, and because the success of an entire venture may hinge on 

 information obtained from the drilling of this test, it is a poor time to economize. 

 Cuttings and cores obtained from the bore hole must be examined and studied 

 by qualified geologists, and electric-log surveys and gamma ray-neutron logs 

 interpreted for lithologies and formation fluids by experts. Extensive coring and 

 drill-stem testing must be conducted to eliminate the possibilities of overlooking 

 potential oil and/or gas reservoirs. A logging unit, which examines the mud 

 and the cuttings from the bore hole for minute traces of oil and gas as the well 

 is drilled, must be employed as well as drilling-time logs to assist the geologist 

 in locating hard and soft drilling breaks. All of these operations must be 

 conducted contemporaneously with the drilling, for unnecessary delays during 

 drilling operations are costly. 



852 



