ABSTRACT

The Paleogene Kugmallit sequence underlies over 20,000 sq. km of the Mackenzie Delta-Beaufort Sea. Selected drill cores from 13 widely spaced wells penetrating Kugmallit delta-plain to distal delta-front facies at depths of 919 to 3937 m contain mainly massive to parallel-bedded siliciclastics with variable bioturbation. Both grain size and sorting decrease in an offshore direction in the modern sediments as well as in the Kugmallit sequence. By analogy with modern sedimentation in the area, most of the Kugmallit offshore sandstones studied were probably deposited in water less than 10 m deep. The petrography of about 170 core samples studied in polished thin sections, supplemented by XRD, SEM and EDXRA data, is compared to corresponding measured values of porosity and permeability and to wireline log response. The results show that improved sorting and an exponential increase in detrital quartzose framework-grain content accompany increasing median grain size. These variations are reflected in reservoir properties and log responses. Coarser grained, better sorted sandstones are characterized by total gamma ray values lower than those of finer grained sandstones. Further, the differences between the neutron and density log porosity values in the coarser sandstones are markedly less than those for finer grained sandstones. Low-magnesian ferroan calcites or calcian to calcian/ferroan dolomites form prominent cements in some of the sandstones, which can be distinguished from noncemented sandstones by high sonic velocities on logs.

End_of_Record - Last_Page 220-------