James P. Rogers¹, Mark W. Longman²

(1) National Geological Services, Inc, Denver, CO
(2) consulting geologist, Lakewood, CO

ABSTRACT: Introduction To Chert Reservoirs of North America

North American hydrocarbon reservoirs in chert and other fine crystalline siliceous rocks are under-reported and only locally recognized by petroleum professionals. As displayed in this poster symposium on North American Chert Reservoirs, documented examples of such reservoirs with major reserves range in age from Devonian to Miocene. They are widely distributed from West Texas (e.g., the Devonian Thirtyone Formation at Dollarhide Field) to British Columbia in Canada (the Devonian Parkland Field). Depositional facies of these reservoirs range from the anhydritic sabkas (Pennsylvanian Amsden Formation at Wolf Springs field in central Montana) to the deep open marine (Miocene Monterey cherts at Elk Hills Field in south-central California). Furthermore prolific Devonian and Mississippian spiculitic chert reservoirs were deposited in deep shelf environments of the Midcontinent and West Texas. Diagenetic processes fundamental to formation of chert reservoirs include very early dissolution and reprecipitation of amorphous biogenic silica (Miocene Monterey), and of potentially great significance, late stage hydrothermal silicification long after burial of pre-existing carbonate sediments (e.g., Parkland Field).

Glick Field, in Kiowa County, Kansas, provides a classic example of a highly porous spiculitic chert reservoir. Like many other Mississippian fields flanking the Central Kansas Uplift, Glick produces from the ìChatî at or near the pre-Pennsylvanian unconformity. The Glick reservoir is a porous ìspiculiteî that will soon produce its 400th BCF of gas. Glick is a truncation trap formed by erosion of a low-relief sponge bioherm/biostrome which originally covered at least 20 square miles. Other ìChatî reservoirs in contrast produce from a variety of lithologies including spiculitic limestones, allochthonous chert pebble conglomerates and dolomitic cherts. This heterogeneity is a small example of that found in chert reservoirs throughout North America.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado