LOG-DERIVED CATION EXCHANGE CAPACITY OF SHALY SANDS: APPLICATION TO HYDROCARBON DETECTION AND DRILLING OPTIMIZATION
Tez Türü: Bütünleşik Doktora
Tezin Yürütüldüğü Kurum: Louisiana State University and Agricultural and Mechanical College, Engineering, Craft and Hawkins Department of Petroleum Engineering, Amerika Birleşik Devletleri
Tez Danışmanı: Dr. Zaki Bassiouini
Tezin Onay Tarihi: 2002
Tezin Dili: İngilizce
Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
Desteklendiği Program: San-Tez Programı
Özet:
ABSTRACT
Researchers at Louisiana State University, LSU, have introduced several
petrophysical models expressing the electric properties of shaly sands. These
models, to be used for hydrocarbon detection, are based on the Waxman and Smits
concept of supplementing the water conductivity with a clay counterions conductivity.
The LSU models also utilize the Dual Water theory, which relates each conductivity
term to a particular type of water, free and bound, each occupying a specific volume
of the total pore space. The main difference between these models and the other
shaly sand models is that the counterion conductivity is represented by a hypothetical
sodium chloride electrolyte.
This study introduces a modified version of early LSU models. This modified
model eliminates a questionable assumption incorporated in all previous shaly sand
models. Previous models use same formation resistivity factor for all terms in the
model. The proposed model considers that the electric current follows the effective
porosity path in the term representing the free electrolyte and follows the clay porosity
path in the term representing bound water. The differentiation between the two paths
is accomplished by using two different formation factors one in the free water and
another in the bound water term of the model. It also used two different cementation
exponents to express formation factors in terms of porosity.
The validity of the new model was checked using cation exchange capacities
measured on core samples and drill cuttings. Calculated cation exchange capacities
display good agreement with the measured cation exchange capacities. The water
saturation calculated using the new model are more representative of hydrocarbon
potential of the zones of interest.
In addition, cation exchange capacity calculated using this modified model and
log data acquired during drilling has shown potential for diagnosis of pending bit
balling of PDC bits drilled with water based mud in overpressured shale.