PETROPHYSICS
Petrophysics is the study of the physical and chemical properties that describe the occurrence and behavior of rocks, soils and fluids. Petrophysicists evaluate the reservoir rock properties by employing well log measurements, in which a string of measurement tools are inserted in the borehole, core measurements, in which rock samples are retrieved from subsurface, and sometimes seismic measurements, and combining them with geology and geophysics.
In this book we will only use the term “Petrophysics” and consider it in its usual common meaning, which is slightly restrictive: study of the physical properties of rocks focusing on the storage and flow of the fluids contained within them. We will investigate more specifically the properties related to the greater or lesser presence of a porous phase inside the rocks. This porosity will play a central role in our descriptions. The raison d’être of Petrophysics, as we will describe it, lies mainly in its relation to petroleum, hydrogeological and civil engineering applications. |
The document is a summary of each common openhole petrophysical measurement; the interpretation goals and details, a brief explanation of the physics and operating constraints, and some of the nomenclature related to each measurement. The measurements are those that have been traditionally used to determine formation lithology, porosity, and fluid saturation. |
This book presents the developed concepts, theories, and laboratory procedures as related to the porous rock properties and their interactions with fluids (gases, hydrocarbon liquids, and aqueous solutions). The properties of porous subsurface rocks and the fluids they contain govern the rates of fluid flow and the amounts of residual fluids that remain in the rocks after all economical means of hydrocarbon production have been exhausted. It is estimated that the residual hydrocarbons locked in place after primary and secondary production, on a worldwide scale, is about 40% of the original volume in place. This is a huge hydrocarbon resource target for refined reservoir characterization (using the theories and procedures of petrophysics) to enhance the secondary recovery or implement tertiary (EOR) recovery.
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Standard Archie water saturation and formation porosity are the two key parameters determined from wireline logs that are used in the evaluation of a subsittface reservoir as a potential hydrocarbon producer. They are measures of reservoir content but not reservoir performance, and by themselves do not provide an actual indication of the hydrocarbon productivity of a reservoir. |
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