The Bedrock Geology and Structure of a Portion of the Upper San Pedro Basin as Penetrated by the Phillips #1-A Huachuca State Trust Well

Moore, William D. ¹, Steve Rauzi² (1) Independent, Hereford, AZ (2) Arizona Geological Survey, Tucson, AZ

Cochise County, Arizona contains a possible southern extension of the Wyoming Overthrust Play pioneered by Anchutz Oil in the late 1970’s. Recent successes in the Utah portion of this play by Wolverine Oil and Gas underscore the necessity of understanding the geology of Cochise County to ascertain whether or not this play extends into the region. If exploration objectives exist, the industry needs to find them. If no objectives exist, that would also be significant information for the industry.

The geology under the basin filling sediments can only be hinted at by the results of surface studies within the mountain ranges Three wells drilled by Phillips Petroleum in the early 1980’s are deep enough to provide data on the geology in the basins. I chose one of these wells -the Phillips Petroleum Huachuca #A-1 State Trust to see what geology was encountered. The well was drilled in the western part of the San Pedro Basin to a depth of 8513 feet and had a full suite of logs and some cores. In addition, I reviewed surface studies of the Whetstone, Huachuca and Mustang Mountains to the west of the well to assist in understanding the geology penetrated by the well.

The Huachuca #A-1 appears to have encountered the Cretaceous Bisbee Group unconformably overlaying late-Paleozoic Naco Group carbonates. This section is thrust over more Bisbee group sediments. It appears the well bottomed in the Bisbee just below another fault No hydrocarbon shows were encountered.

AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana