Stratigraphic and Tectonic Framework of the U.S. Chukchi Shelf: Exploration Insights from a New Regional Deep-Seismic Survey

Naresh Kumar, James Granath, Pete Emmet, and Menno G. Dinkelman
ISS - GX Technology, ION Geophysical, Houston, TX.

The remote Chukchi Shelf, a highly prospective petroleum province offshore northwest Alaskan, has seen only one leasing round (early 1990’s). However, in February 2008 at the first lease sale in 17 years, seven groups bid a total of US$ 2.7 billion on 488 blocks.

In late 2006, ION Geophysical (GX Technology) acquired 3,132 km of 2-D long-offset seismic data in the area. The program was designed to image down to the base of the crust with a 9-km long cable, 18-second recording, and final depth processing to 40 km.

Stratigraphic sequences recognized and tied to well penetrations in the area are the same as those reocognized in the prolific North Slope of Alaska, i.e., the Brookian (Upper Cretaceous-Tertiary), Beaufortian (Lower Cretaceous), and Ellesmerian (Upper Devonian-Jurassic). An active petroleum system exists, as identifed by drilling, but except for the Burger accumulation, no potential economic accumulations have been recognized. Our data suggests that flanks of platforms - Arctic as well as the Chukchi - offer opportunities for additonal plays. Furthermore, the new data have extended the coverage into the North Chukchi Basin, where up to 12,000 meters (40,000 feet) of Brookian and Beaufortian sediments might present other potential targets. The underlying “acoustic basement” is recognized as the top of the Franklinian (pre-Upper Devonian) sequence. However, prior to the deposition of the Ellesmerian sequence, the Franklinian sequence underwent a complex history of rifting, inversion, basement-involved thrusting, uplift and erosion as shown by a reconstruction of a profile that traverses the Arctic Platform in the northeast part of the area. At least part of this sequence appears to be represented by mildly-deformed Paleozoic and upper Proterozoic rocks with a stratigraphy similar to that of rocks present in the Melville Island and vicinity in the Canadian Arctic. Thus, a petroleum potential for this sequence should not be completely ruled out. Along with the sedimentary sequences, we have also regionally mapped the top of the crystalline basement and the MOHO discontinuity. This crustal-level imaging and interpretation in depth have allowed identification of previously untested plays in the basin. In addition, these data should also facilitate in developing a framework for the Russian Chukchi Shelf, which remains completely untested.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia