S. George Pemberton¹, Murray K. Gingras², Floyd Henk¹

(1) University of Alberta, Edmonton, AB
(2) University of New Brunswick, Fredricton, NB

ABSTRACT: Assessing Permeability in Bioturbated Media

In the past, trace fossil research in hydrocarbon reservoir rocks was almost always confined to exploration geology, however, recent research is showing that ichnology has significant applications in production geology. Current research indicates that substrate controlled ichnofossil assemblages can enhance the permeability and vertical transmissivity of a relatively impermeable matrix. Permeability enhancement develops when burrows into a firm ground are filled with sediment from the overlying strata. If the lithology contrasts with the encapsulating firm ground substrate, anisotropic porosity and permeability is developed. The same concept can be applied to carbonate reservoirs where the burrows are subjected to different diagenetic phases. This again results in anisotropic permeability that can have dramatic effects on reserve calculations. If the burrows have enhanced permeability reserve calculations will be too low. Likewise if the burrows have lowered permeability the reserve calculations may be too high. Understanding the flow dynamics of the anisotropic permeability provides a potentially powerful reservoir development tool. The implications of such understanding are far reaching, particularly pertaining to calculations of reserves and deliverability. Three inter related areas are under examination in order to develop quantitative models: A. The Devonian Wabamun Formation in Alberta is a platform carbonate and contains burrowed facies that have enhanced permeability and standard reserve calculations will be under estimated; B. The Ordovician Yeoman Formation in Saskatchewan is a platform carbonate that contains burrowed facies that have reduced permeability, in this example standard reserve calculations will be over estimated; and C. The role of Glossifungites burrows in reservoir dynamics including permeability enhancement, reserve calculations and deliverability of hydrocarbons in reservoirs; specific examples include the Triassic Sag River Formation in Alaska, the Jurassic Arab D in Saudi Arabia, and the Miocene Mirador Fm

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