Abstract

Carbonates of the Upper Pennsylvanian Cisco and Canyon formations are major hydrocarbon reservoirs throughout the Permian Basin. The most-readily recognized and described reservoir trend associated with these rocks is the Horseshoe Atoll in the Midland Basin. Horseshoe Atoll is composed of stacked algal mound reservoirs of disparate ages that are developed in the Canyon, Cisco and overlying Wolfcamp beds. Other Upper Pennsylvanian fields are found scattered throughout the North Platform and Eastern Shelf along the margins of the Midland Basin. On the New Mexico side of the Permian Basin, the most notable production from Cisco-Canyon carbonates is from Indian Basin and Dagger Draw Fields, and in the Tatum Basin.

Indian Basin and Dagger Draw Fields are located on the Northwest Shelf of the Permian Basin in Eddy County, New Mexico and are known for their prolific production of natural gas (Indian Basin) and dual phase (oil and gas) hydrocarbons (Dagger Draw). Production at Indian Basin is from a multi-sequence, dolomitized algal mound complex that developed along a composite Cisco shelf edge that coincided with a tectonically active, faulted margin. Dagger Draw Field production is from several discrete Canyon sequences that are laterally in proximity to one another. Other Cisco-Canyon production in the area is from more isolated occurrences of porous, algal limestones.

There have been few new discoveries in the Cisco-Canyon in New Mexico partly because outside of Dagger Draw, Indian Basin, and the Tatum Basin area, production is spotty. However, where the Cisco-Canyon has been targeted, exploration focused on larger mound sequences. In many other areas of the Northwest Shelf, the Cisco-Canyon was overlooked in favor of deeper targets. Smaller, one- and two-well fields in the Cisco-Canyon are capable of economical production, and many additional analagous features await discovery.

A depositional model is proposed that explains the patterns and geometries of Cisco-Canyon mound sequences on the Northwest Shelf. This model borrows from concepts developed from more detailed studies of the Cisco-Canyon in the Midland Basin. The Cisco-Canyon on the Northwest Shelf was deposited as a series of discrete, time-stratigraphic sequences that are spread out laterally a distance of over 20 miles across the shelf. This depositional style was in response to the same glacio-eustatic influences that affected deposition of coeval rocks in the Midland Basin.

An exploration model for finding more subtly-expressed Cisco-Canyon reservoir mounds is proposed. The model is based on preliminary assessment using subsurface mapping, sample analysis, and 2-D seismic data. Follow-up assessment by 3-D seismic can high-grade targets once the basic fairway trends are defined by the preliminary assessment.