Microgravity Techniques Assessing New Potential in an Existing Giant Field: Teapot Dome

Sandra K. Raeuchle, Brett A. Huffman, Dinesh S. Fernando, Erin D. Duffey, and Richard G. Talbert
Electro-Seise, Fort Worth, TX

Teapot Dome Field, Natrona County, Wyoming is in the top 100 largest fields in the United States with proven reserves of 42,515,000 bbl. The field has been exploited in the Upper Cretaceous Shannon, Second Wall Creek Sandstones as well as the Pennsylvanian Tensleep. We at Electro-Seise (ESI) found additional potential in the unexploited and fractured Upper Cretaceous Niobrara Shales and the Lower Cretaceous Muddy Sandstones. Several million barrels of oil remain in the subsurface yet to be drilled.

Airborne micro-gravity was used in this study to determine this potential. Acquisition techniques utilized a passive sensor similar to old torsion balance types used to define salt domes in the Gulf Coast. Total potential field signals are measured and then state-of-the-art digitally processed, producing a three-dimensional micro-gravity cube for the recognition of movable hydrocarbons at depth.

Three dimensional seismic was merged with the gravity data. Structural maps were derived matching the hydrocarbon “depth slices” through the prospective horizons. New potential pools conform to structure, giving the interpretation a good confidence level. The 3D seismic structure maps show doubly-plunging anticlines with very steep-dips, particularly on the western flank. These structures are set up deep within the basement rocks by lateral and compressional movement, expressed as a flower structure.

Horizontal wells should be considered, particularly in the fractured Niobrara Shales. An early DST in the Niobrara flowed 25,000 bopd. Clearly this sort of potential, combined with bypassed Muddy Sandstone pay would provide economic wells with quick payouts.