Surficial Fracture Mapping for Unconventional Reservoirs Rio Puerco Structure, New Mexico

Reynolds, Santiago M.

Oil production is attributable to fractured shale and siltstone of the Rio Puerco structure situated in the San Juan Basin, New Mexico. In order to understand the possible controlling influence of surficial fractures to reservoir fractures, the author identified fractures observable on aerial photographs, and then posted them to 7.5 minute topographical quadrangles with a 1:24,000 scale. The alignment of fracture segments enabled a continuity interpretation indicating the orientation of large primary fractures versus many smaller localized ones.

Rio Puerco surface drainage patterns were grouped and used to delineate related areas that likely reflect higher elevation bedrock surfaces under alluvium. Plotting the fracture and geomorphic information together shows that areas of fracture intersection correlate reasonably well to known oil fields with fracture controlled production, and similar patterns elsewhere might indicate other areas that have yet to be explored with surficial fracture trends in mind. Lacking dense vegetation, the Rio Puerco area lends itself to surficial fracture assessment.

While somewhat unconventional, the aerial photographic method of identifying surficial fractures is not new, it is an aspect of field geology, though it typically is not mentioned in the context of petroleum E&P. The author first used the method while employed by Pemex in 1970 to successfully position gas/condensate wells in northern Mexico across from Maverick Co. TX, and again in the mid-80s in South Africa to investigate anomalous shallow gas from crystalline rocks of the Transvaal. Formerly a pencil and paper exercise, surface fractures are now mapped electronically with much greater efficiency and for more effective interpretation.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013