Non-seismic geophysics compared and integrated with seismic in a frontier oil play: Northern Sangre de Cristo Mountains/Northeast San Luis Basin, Colorado

Four non-seismic geophysical tools have made a significant contribution to a new geological interpretation of the northern Sangre de Cristo Mountains/northeast San Luis Basin of south-central Colorado. Gravity, aeromagnetic, magnetotelluric, (MT) and time domain electromagnetic (TDEM) data were acquired and interpreted during the early stages of exploration. Two-dimensional modeling of the gravity and magnetics placed the main, basin-bounding fault three miles southwest of the mountain front, identified an intermediate fault block at the basin margin and identified a thick sequence of non-magnetic, intermediate density rocks on top of this block. A thick section of Mesozoic sediments is interpreted, supported by the discovery of outcrops of Cretaceous sediments and live Cretaceous oil. Magnetotelluric data was acquired to confirm the presence of Mesozoic sediments and depth to basement. Detailed TDEM data has been useful in correlating the MT with surface geology. Integration of the gravity, magnetic and MT data with seismic resulted in minor modifications to the new geological model.