TY - JOUR
T1 - Effect of kerogen on rock physics of immature organic-rich chalks
AU - Shitrit, Omri
AU - Hatzor, Yossef H.
AU - Feinstein, Shimon
AU - Palchik, Vyacheslav
AU - Vinegar, Harold J.
N1 - Funding Information:
This research was funded by Israel Energy Initiatives, Ltd. (IEI) through BGU contract No. 87244811 . We thank IEI scientists Dr. Yoav O. Rosenberg, Dr. Itay J. Reznik and Dr. Scott V. Nguyen for fruitful discussions and for joyful cooperation. We thank Leonardo Freitas and Edna Danon for TOC measurements and their great assistance in sample preparation. The senior author thanks Israel Ministry of Infrastructures, Energy and Water Resources for a fellowship awarded to graduate students performing research in petroleum geosciences. Roxana Golan from the Microscopy Unit, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, is thanked for the assistance in scanning the samples in SEM.
Publisher Copyright:
© 2016 Elsevier Ltd.
PY - 2016/5/1
Y1 - 2016/5/1
N2 - We study the rock physics of organic-rich chalk from the Shefela basin, central Israel, based on laboratory measurements of core material from the Zoharim well. This deposit is an immature source rock that includes the Late Cretaceous Ghareb and Mishash formations. The studied rock is composed of three dominating phases: minerals, kerogen, and pores. We investigate how porosity and kerogen influence the physical behavior of the rock, based on measurements of porosity, density, acoustic velocities, elastic moduli, tensile strength and compressive strength. We find that the dynamic bulk modulus and the static Young's modulus decrease with increasing kerogen content as well as with increasing porosity. To describe the stiffness of the solid skeleton we use two different poroelasticity models for fluid substitution assuming material isotropy: Biot-Gassmann model and Marion's BAM model. The obtained poroelasticity coefficients indicate a soft matrix composed of kerogen-micrite mixture, characterized by a low BAM normalized stiffness factor (w ~ 0.2) and a high Biot coefficient (β ~ 0.9). These values appear to vary with changes in kerogen content, grain size and degree of cementation. Porosity, which typically decreases with depth in the studied basin, does not show a clear correlation with kerogen content. Moreover, both compressive and tensile strengths decrease linearly with increasing porosity, regardless of kerogen content. We use a density-kerogen relationship to create a porosity depth profile, by combining data from continuous cores and density well logs. By comparing sonic logs with laboratory measurements of P-wave velocities on fully-saturated cores, we are able to detect a gas zone in the shallow interval of the sequence in the studied well.
AB - We study the rock physics of organic-rich chalk from the Shefela basin, central Israel, based on laboratory measurements of core material from the Zoharim well. This deposit is an immature source rock that includes the Late Cretaceous Ghareb and Mishash formations. The studied rock is composed of three dominating phases: minerals, kerogen, and pores. We investigate how porosity and kerogen influence the physical behavior of the rock, based on measurements of porosity, density, acoustic velocities, elastic moduli, tensile strength and compressive strength. We find that the dynamic bulk modulus and the static Young's modulus decrease with increasing kerogen content as well as with increasing porosity. To describe the stiffness of the solid skeleton we use two different poroelasticity models for fluid substitution assuming material isotropy: Biot-Gassmann model and Marion's BAM model. The obtained poroelasticity coefficients indicate a soft matrix composed of kerogen-micrite mixture, characterized by a low BAM normalized stiffness factor (w ~ 0.2) and a high Biot coefficient (β ~ 0.9). These values appear to vary with changes in kerogen content, grain size and degree of cementation. Porosity, which typically decreases with depth in the studied basin, does not show a clear correlation with kerogen content. Moreover, both compressive and tensile strengths decrease linearly with increasing porosity, regardless of kerogen content. We use a density-kerogen relationship to create a porosity depth profile, by combining data from continuous cores and density well logs. By comparing sonic logs with laboratory measurements of P-wave velocities on fully-saturated cores, we are able to detect a gas zone in the shallow interval of the sequence in the studied well.
KW - Acoustic velocity
KW - Compressive strength
KW - Kerogen
KW - Organic-rich chalk
KW - Poroelasticity
KW - Porosity
KW - Source rock
KW - Tensile strength
UR - http://www.scopus.com/inward/record.url?scp=84961620672&partnerID=8YFLogxK
U2 - 10.1016/j.marpetgeo.2016.03.023
DO - 10.1016/j.marpetgeo.2016.03.023
M3 - Article
AN - SCOPUS:84961620672
SN - 0264-8172
VL - 73
SP - 392
EP - 404
JO - Marine and Petroleum Geology
JF - Marine and Petroleum Geology
ER -