Induced polarization effect in reservoir rocks and its modeling based on generalized effective-medium theory

One of the major tasks of the petroleum resource-efficient technologies (pREFFIT) is the development and improvement of the methods of exploration for energy resources. This review paper summarizes the results of the research on induced polarization (IP) effect in reservoir rocks conducted by the University of Utah Consortium for Electromagnetic Modeling and Inversion (CEMI) and TechnoImaging. The electrical IP effect in hydrocarbon (HC) bearing reservoir rocks having nonmetallic minerals is usually associated with membrane polarization, which is caused by a variation in the mobility of the ions throughout the rock structure. This mobility is related to the size and shape of the pores filled with electrolyte and the double electrical layers. We have studied the IP response of multiphase porous systems by conducting complex resistivity (CR) frequency-domain IP measurements for two different groups of samples: sands and sandstones containing salt water in pores and those whose unsaturated pores were filled with synthetic oil. We have also studied selected carbonate reservoir formations, typical of some major HC deposits

Free Energy Driven Transfer of Charge in Dense Electrochemically Active Monomolecular Films

The interest in monomolecular films as electric conductors arises from the search for innovative materials. The utility of non-covalently bonded films is limited because they are mechanically unstable and consist of poorly connected domains. Consequently, charge transfers in these films are limited to the distances in the order of a micrometer. Here we show that a recently developed gas phase assembling method (Burtman, V., Zelichenok, A., Yitzchaik, S. (1999) Angewandte Chemie Inter. Ed. 38, 2041-2045.), which produces robust dense monolayers of NTCDI covalently attached to the surface of silicon, allows one to overcome this scale limitation. These virtually insulating monolayers can be photo-chemically populated with cation-radicals via ejection of electrons into the semi-conducting base. The positive charges of cation-radicals can migrate as far as several millimeters within microseconds in a random walk fashion thus demonstrating the macroscopic connectivity of the film. Since the charges exist as cation-radicals, which are potent oxidants, their migration is coupled to transfer of the free energy of their reduction and is driven by the redox potential gradient. Reduction of cation-radicals by an anode converts this free energy into electromotive force. We show how these films can be implemented in solar energy conversion and basic time-resolved distance-controlled studies of sequences of ultra-fast electron transfers.Comment: 18 pages, 4 figure

Molecular Photovoltaics in Nanoscale Dimension

This review focuses on the intrinsic charge transport in organic photovoltaic (PVC) devices and field-effect transistors (SAM-OFETs) fabricated by vapor phase molecular self-assembly (VP-SAM) method. The dynamics of charge transport are determined and used to clarify a transport mechanism. The 1,4,5,8-naphthalene-tetracarboxylic diphenylimide (NTCDI) SAM devices provide a useful tool to study the fundamentals of polaronic transport at organic surfaces and to discuss the performance of organic photovoltaic devices in nanoscale. Time-resolved photovoltaic studies allow us to separate the charge annihilation kinetics in the conductive NTCDI channel from the overall charge kinetic in a SAM-OFET device. It has been demonstrated that tuning of the type of conductivity in NTCDI SAM-OFET devices is possible by changing Si substrate doping. Our study of the polaron charge transfer in organic materials proposes that a cation-radical exchange (redox) mechanism is the major transport mechanism in the studied SAM-PVC devices. The role and contribution of the transport through delocalized states of redox active surface molecular aggregates of NTCDI are exposed and investigated. This example of technological development is used to highlight the significance of future technological development of nanotechnologies and to appreciate a structure-property paradigm in organic nanostructures