Assessment of
Permeability and Porosity Using
Kenter, J.A.M.1, O.
Vizika2, E. Rosenberg2, M. Skalinski3, P.M.
Harris4, M. Buoniconti4 (1) Chevron ETC, Voorburg, Netherlands (2) Institut
Français du Pétrole, Paris, France (3) TengizChevroil,
Atyrau, Kazakhstan (4) Chevron Energy Technology
Company, San Ramon, CA
The central platform in the Tengiz buildup contains a succession of cyclic shallow water
deposits ranging from Famennian to Bashkirian in age. The upper Visean,
Serpukhovian, and Bashkirian
form the main hydrocarbon-bearing interval and contain cyclic, depositional
cycles ranging from dm- to m-scale to 10's of meters in. The distribution of
reservoir rock types in the central platform is determined by a combination of
primary deposition and burial diagenetic modification
and includes spatial variations of both porosity enhancing (corrosion) as well
as porosity filling (reducing) effects.
A pilot study using a combination of pore
network modeling of the petrophysical properties from
high resolution (~1 micron) CT microscanner imagery
of several selected plug samples resulted in spatial pore and pore-throat size
distributions, level and type of pore interconnectivity as expressed by the
aspect ratio as well as the coordination numbers (number of pore throats per
pore). Porosity, permeability, capillary pressure and formation factors were
estimated from CT and NMR analyses and show a close match with those derived
from analytical measurements. Most strikingly, the CT imagery allowed the
extraction of the 3D distribution of pore type and connectivity as well as
cement types, information essential to reservoir quality assessment but very
difficult to reconstruct using the classic petrographic
approach.
High resolution CT and NMR imagery of key
reservoir intervals provide reliable data on rock properties and, more
importantly, they fill the essential link between petrophysics
and geology at the scale of even small pore types (~1-3 microns) and pore filling cements.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California