Surficial Fracture Patterns in the Niobrara-Mancos Shale of Eastern Rio Arriba County, New Mexico and Applicability to Four Corner Basins
Oil production attributable to fractured shale and siltstone of the Niobrara-Mancos is found in the Puerto Chiquito, East Puerto Chiquito and Boulder Mancos fields of eastern Rio Arriba County, 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. Surficial 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 basins of the Four Corners area lend themselves to surficial fracture assessment. The aerial photographic method of identifying surficial fractures is not new, 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 adjacent to Maverick Co., TX, and again in the mid-80's in South Africa to investigate anomalous shallow gas from crystalline rocks of the Transvaal. Fracture distribution is not the end point of any exploration effort, though in the areas of fracture-enhanced production, it can be a useful tool to better delineate areas worthy of further investigation with subsurface geology and geophysics.
AAPG Search and Discovery Article #90156©2012 AAPG Rocky Mountain Section Meeting, Grand Junction, Colorado, 9-12 September 2012