AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Basin Evaluation Comparison: Paradox, San Juan and Black Mesa Basins Utah, Colorado, New Mexico and Arizona, USA
(1) Integrated Geophysics Corp., Houston, TX.
(2) BP North American Gas, Houston, TX.
Subsurface technical studies conducted in the 4-Corners region of New Mexico, Utah, Colorado, and Arizona provide geoscientists a view of the tectonic history of the basins. The Paradox, San Juan and Black Mesa basins, although located adjacent to each other and separated by the Defiance Uplift, have different basin histories resulting in very different hydrocarbon productivity and prospectivity.
GM Geophysics generally broad in coverage provides a cost effective tool to guide interpretations. The integration of GM geophysical data in the form of gravity and magnetic, with other available data, provides an approach to evaluate the early history of each basin. We were able to construct a suite of maps and a regional cross-section stretching across basins, from the Grand Canyon in the west to the Nacimiento uplift in the east. The cross-section incorporates all the available data and allows for evaluation of the basins.
The Paradox and San Juan basin show late Paleozoic sediments (Mississippian-Pennsylvanian), primarily carbonates similar to those seen in the Paradox Basin to the NW, while the Black Mesa basin shows early Paleozoic sediments, similar to those seen in the Grand Canyon to the West. In fact, the Grand Canyon exposes Proterozoic Chuar Fm., sediments that may have source rock potential, deposited in an ancient rift basin. The extent of this rift basin is uncertain but through the use of GM geophysics, we were able to model the potential eastward extension of this source rock into the Black Mesa basin.
The Mesozoic history of the basins also differ and impact the hydrocarbon richness of the basins. The San Juan basin is filled with a thick sequence of sandstones, shales, and coals. Similar lithologies in the Black Mesa basin are thin due to later uplift and erosion and are totally missing in the Paradox. Structurally the basins are also different due to early tectonic lineaments and later mechanical stratigraphy related to sedimentation. A magnetically-derived basement structure map represents the surface of the crystalline rock.
The exploration potential of the Black Mesa basin was evaluated as high risk due to the generally low yield expected from potential Chuar-type source rocks. Through the integration of GM geophysical data with other existing data and comparison with neighboring basins, the need for a regional grid of 2D seismic data was down-graded.