A Multi-Physics Approach for High-Grading Oil Prospectivity within the Lower Mancos Shale of the San Juan Basin

Abstract:

A multi-measurement, geological and geophysical basin study was undertaken in the south central portion of the San Juan Basin of New Mexico. Data acquisition in the fall of 2014 included gravity, magnetic, radiometric, and electromagnetic data. All acquired datasets were interpreted and integrated with existing 2D seismic and well data to evaluate a 1000 square mile study area for lower Mancos oil prospectivity.

The multi-method integration was successfully able to map a dominant structure identified as the Central Basin High (CBH) that bisects the study area and was revealed in the gravity, seismic, and well datasets. The Central Basin High appears to have its origin during the Ancestral Rockies Orogeny and has impacted both Cretaceous deposition patterns and oil maturity. Detailed basement structure and lithology maps were created. Three major fault sets that bound basement blocks of various sizes and lithologies were identified. Modeled blocks with greater susceptibility and density values were interpreted as Proterozoic granodiorite and quartz monzonite intrusions.

Oil production data for the lower Mancos shale was qualitatively and quantitatively compared with interpreted geophysical and geological datasets. Qualitative relationships were established between oil and gas occurrences and basement structure, reservoir resistivity, and heat flow. Quantitative relationships were made using predictive analytics. Mapping these relationships identified several prospective lead areas within the study area, determining a higher prospectivity for 17% of the 1000 square mile study area. Two premier areas for the primary sandstone target (Tocito) enclosed within the lower Mancos shale were high-graded encompassing 48 square miles of the study area. Predicted oil production was mapped for initial and monthly production, total cum, and EUR/1000 feet. Predicted net remaining EUR was calculated for each township within the study area, providing more informed guidance for exploration and exploitation decision making.