Отправлено: 06.11.12 11:23. Заголовок: A Critical Review to Evaluate NMR Estimated Permeability

The Impact of Pore Geometry Aspects on Porosity- Permeability Relationship - A Critical Review to Evaluate NMR Estimated Permeability
Ahmed Salah, Petrobel
Copyright 2012, Society of Petroleum Engineers


Abstract
The permeability prediction is of extreme importance in hydrocarbon reservoir management. The reservoir rocks are made up
of grains, cement and pore network. The pore network is made up of larger spaces, referred to as pores, which are connected
by small spaces referred to as throats. The pore spaces control the amount of porosity, while the pore throats control the
movement of fluids and the quantity of rock permeability.

The core analysis data for 219 sandstone and limestone sample s were available. The data include porosity, permeability and
capillary pressure by mercury injection. These samples represent 21 stratigraphic units. The geologic age varied between
Cretaceous and Pliocene. Sandstone reservoirs are repres ented by 179 samples, while 40 samples represent carbonate
reservoirs. The data were collected from different geographic areas within Egypt.

Pore-throat size distribution parameters were calculated from the data of capillary pressure. These data were used to
approximate the distribution of pore volume accessible by throat of a given effective size. A new definition for micro-porosity
was proposed based on pore throat size distribution. These data was used to descriminate the sample porosity into micro and
macro porosity based on a pore throat cutoff, which was determined from the relationship betw een storage and flow capacity
of the pore network. The relationship between permeability and aspects of pore geometry; micro-porosity, macro-porosity and
pore throat parameters have been analyzed and discussed.

The interpretation of the results indicates that the permeability is mainly a function of pore-throat size distribution while t he
amount of the porosity or the porosity conf iguration is not the main factor that controls the amount of permeability. A new
model for permeability prediction was devel poed which incorporate the pore space and pore throat. The obtained results have
shown the great influence of pore throat on permeability prediction.