Seven Major Needs for Petroleum Exploration of U.S. Northwest Region

Mont M. Warner

Regional geologic setting, local surface geology, and seismic refraction support the concept of the Snake River downwarp as a rift valley, separate and distinct from the Basin and Range province. The Idaho rift needs to be traced through Oregon and Washington to its probable site of origin in the Pacific basin.

The original Willamette-Puget Sound early Tertiary depression is a prime target for petroleum exploration in light of recent discoveries. The outer limits of this basin need clarification.

Good understanding of surface stratigraphic relationships would greatly aid subsurface structural interpretation in the region. Better dating and correlation of Cenozoic outcrops are needed.

Much of the petroleum potential of the region requires unmetamorphosed Mesozoic and Paleozoic subsurface sections. To postulate this condition, a better understanding is needed of the nature of the metamorphic terrane--are they mostly of the contact type or can we expect a general regional type, at drilling depths throughout the region?

Seismic reflection interpretation in this region has been difficult and not very successful. More and different geophysical experimenting is needed--refraction fan shooting might locate shallow to intermediate depth plutonic domes. The transitional zone between miogeosynclinal facies and eugeosynclinal facies is important to the search for petroleum source materials, reservoir beds, and trap conditions. This zone needs to be defined more accurately and traced through Oregon and Idaho.

Three strategically spaced, deep boreholes (20,000-25,000 ft) are needed to solve these problems and would add greatly to our understanding of the total regional setting. One well site should be within or near the Quincy basin in Washington, one near the Steens Mountain, Oregon, and one in the western Snake River downwarp of Idaho, near Lake Lowell.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.