TY - BOOK

T1 - New Concepts for Understanding the Effects of Complex Pore Structures on Petrophysical Properties of Carbonate Rocks

AU - Müller, Edith

N1 - no embargo

PY - 2013

Y1 - 2013

N2 - Important reservoir properties such as porosity or permeability controlling reservoir storativity and productivity are critically influenced by pore space characteristics, which cannot be reduced on a purely volumetric effect. Pore size, pore shape and interface effects exert the strongest influence and the relationships between these properties are not well understood yet. Pore space properties are especially complex in carbonate rocks, where diverse pore types and pore geometries, as well as complicated pore structures (different scales, shapes and connectivities) exist. In this study, experimental investigations combining different measurement techniques and results of model calculations for carbonate reservoir rocks were used to achieve a better understanding of parameters controlling electrical and hydraulic conductivity (permeability). A modified Archie relationship for water-saturated carbonate rocks has been developed, considering electrically relevant pore types (interparticle, fracture and connected vug porosity; i.e. effective porosity) and separate vugs, which contribute only marginally to electrical conductivity. Central to this concept is the application of two Archie exponents: Exponent m related to connected porosity and exponent m* related to total porosity. Regressions for calculation of exponent m and effective porosity from total porosity and resistivity data have been established for a partitioning of total porosity derived from porosity logs into interparticle, fracture and separate vug porosity. New capillary type pore models have been developed for interparticle porosity covering curved and cone-shaped pore geometries. They numerically explain the influence of pore body and pore throat radius on all considered properties (porosity, specific surface, permeability, electrical resistivity) for “non-cylindrical” pore channels. Model equations deliver three essential results: (1) The mostly empirically formulated influences of pore shape on the petrophysical properties investigated could be covered by the models and their effect on these parameters could be calculated. (2) Using this information, empirically derived parameters (RQI, FZI) can be explained by the models. (3) The identified influencing factors (pore size, ratio of pore body to pore throat radius, tortuosity, porosity) are covered separately in the equations representing the parameters investigated, which allows an individual analysis.

AB - Important reservoir properties such as porosity or permeability controlling reservoir storativity and productivity are critically influenced by pore space characteristics, which cannot be reduced on a purely volumetric effect. Pore size, pore shape and interface effects exert the strongest influence and the relationships between these properties are not well understood yet. Pore space properties are especially complex in carbonate rocks, where diverse pore types and pore geometries, as well as complicated pore structures (different scales, shapes and connectivities) exist. In this study, experimental investigations combining different measurement techniques and results of model calculations for carbonate reservoir rocks were used to achieve a better understanding of parameters controlling electrical and hydraulic conductivity (permeability). A modified Archie relationship for water-saturated carbonate rocks has been developed, considering electrically relevant pore types (interparticle, fracture and connected vug porosity; i.e. effective porosity) and separate vugs, which contribute only marginally to electrical conductivity. Central to this concept is the application of two Archie exponents: Exponent m related to connected porosity and exponent m* related to total porosity. Regressions for calculation of exponent m and effective porosity from total porosity and resistivity data have been established for a partitioning of total porosity derived from porosity logs into interparticle, fracture and separate vug porosity. New capillary type pore models have been developed for interparticle porosity covering curved and cone-shaped pore geometries. They numerically explain the influence of pore body and pore throat radius on all considered properties (porosity, specific surface, permeability, electrical resistivity) for “non-cylindrical” pore channels. Model equations deliver three essential results: (1) The mostly empirically formulated influences of pore shape on the petrophysical properties investigated could be covered by the models and their effect on these parameters could be calculated. (2) Using this information, empirically derived parameters (RQI, FZI) can be explained by the models. (3) The identified influencing factors (pore size, ratio of pore body to pore throat radius, tortuosity, porosity) are covered separately in the equations representing the parameters investigated, which allows an individual analysis.

KW - specific electrical resistivity

KW - total porosity

KW - effective porosity

KW - permeability

KW - carbonate rocks

KW - capillary tube model

KW - Archie relationship

KW - pore body radius

KW - pore throat radius

KW - specific surface

KW - pore space geometry

KW - interparticle pores

KW - fractures

KW - vugs

KW - nuclear magnetic resonance

KW - spezifischer elektrischer Widerstand

KW - totale Porosität

KW - effektive Porosität

KW - Permeabilität

KW - Karbonatgesteine

KW - Kapillarmodell

KW - Archie-Beziehung

KW - Porenkörperradius

KW - Porenhalsradius

KW - spezifische innere Oberfläche

KW - Porenraumgeometrie

KW - Interpartikelporosität

KW - Klüfte

KW - Vug-Porosität

KW - nuklearmagnetische Resonanz

M3 - Doctoral Thesis

ER -